ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
Filter
  • Artikel  (4.317)
  • Polymer and Materials Science  (4.317)
  • Cell & Developmental Biology
  • Electronic structure and strongly correlated systems
  • Animals
  • Chemical Engineering
  • Technik allgemein  (4.317)
Sammlung
  • Artikel  (4.317)
Schlagwörter
Verlag/Herausgeber
Erscheinungszeitraum
  • 1
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 77-85 
    ISSN: 0021-9304
    Schlagwort(e): implant ; titanium ; osteoblasts ; surface roughness ; 1α,25- (OH)2D3 ; differentiation ; local factor ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Surface roughness has been shown to affect differentiation and local factor production of MG63 osteoblast-like cells. This study examined whether surface roughness alters cellular response to circulating hormones such as 1α,25-(OH)2D3. Unalloyed titanium (Ti) disks were pretreated with HF/HNO3 (PT) and then were machined and acid-etched (MA). Ti disks also were sandblasted (SB), sandblasted and acid etched (CA), or plasma sprayed with Ti particles (PS). The surfaces, from smoothest to roughest, were: PT, MA, CA, SB, and PS. MG63 cells were cultured to confluence on standard tissue culture polystyrene (plastic) or the Ti surfaces and then treated for 24 h with either 10-8M or 10-7M 1α,25-(OH)2D3 or vehicle (control). Cellular response was measured by assaying cell number, cell layer alkaline phosphatase specific-activity, and the production of osteocalcin, latent (L) TGFβ, and PGE2. Alkaline phosphatase activity was affected by surface roughness; as the surface became rougher, the cells showed a significant increase in alkaline phosphatase activity. Addition of 1α,25-(OH)2D3 to the cultures caused a dose-dependent stimulation of alkaline phosphatase activity that was synergistic with the effect caused by surface roughness alone. 1α,25-(OH)2D3 also caused a synergistic increase in osteocalcin production as well as local factor (LTGFβ and PGE2) production on the rougher CA, SB, and PS surfaces, but it had no effect on the production on smooth surfaces. The inhibitory effect of surface roughness on cell number was not affected by 1α,25-(OH)2D3 except on the SB surface. 1α,25-(OH)2D3 decreased cell number, increased alkaline phosphatase activity and osteocalcin production, and had no effect on LTGFβ or PGE2 production by MG63 cells grown on tissue culture polystyrene. These data suggest that bone cell response to systemic hormones is modified by surface roughness and that surface roughness increases the responsiveness of MG63 cells to 1α,25-(OH)2D3. They also suggest that the endocrine system is actively involved in normal bone healing around implants. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 77-85, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 2
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 102-119 
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: An investigation was performed to study the mechanical performance of fiber-reinforced composite hip prostheses. In Part I of the study, a three-dimensional finite element code was developed for analyzing a composite hip prosthesis in a femur. The material properties of the composite were treated as anisotropic and inhomogeneous while the properties of the femoral bone were treated as anisotropic and homogeneous. All the materials were assumed to behave linear-elastically. Thermoplastic graphite/PEEK material was selected for the study. No slippage was assumed at the interface between the implant and the surrounding femoral bone. In Part II, numerical simulations were performed using the code to study the performance of a composite prosthesis in the femur. The stress/strain distributions, micromotions, and strain energy density of the surrounding femoral bone were evaluated and found to be related to initial fixation and long-term stability of the prosthesis in the femur. Numerous fiber orientations were studied, and the results of the calculations were compared with those generated from a prosthesis made of cobalt chrome and Ti-6Al-4V titanium alloys. Based on the analysis, it was shown that compared to conventional metallic implants more favorable stresses and deformations could be generated in the femur using composite implants. In addition, by changing fiber orientations according to femoral loads, a composite implant could be designed specifically for the left or the right femur. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 102-119, 1998.
    Zusätzliches Material: 21 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 153-160 
    ISSN: 0021-9304
    Schlagwort(e): low-contact stress prosthesis ; polyethylene failure ; total knee arthroplasty ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: From January 1985 to December 1990, 598 consecutive New Jersey low-contact stress (LCS) total knee arthroplasties (TKAs) were performed for gonarthrosis. Among these 598 operations, 322 were with rotating platform elements and 276 were with meniscal bearing elements. During 5 to 8 years of follow-up, eight knees had severe symptomatic polyethylene failure that required revision surgery; all eight cases were meniscal bearing types. The failed polyethylene inserts were retrieved and studied. It was observed that there were four probable failure mechanisms associated with the catastrophic polyethylene wear. First, insufficient thickness of the meniscal bearing was the major reason for wear. Second, the malpositioning of the metal tibial tray in the transverse plane resulted in the breaking of the meniscal bearing. Third, the inability of the patellar to rotate due to tissue ingrowth made the polyethylene break. Last, yellowing of the subsurface of the meniscal bearing was a sign of polyethylene failure. These four possible failure mechanisms are all associated with the design of the meniscal bearing type of LCS knee prostheses. Therefore, it is suggested that the design of the LCS knee prosthesis should be modified. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 153-160, 1998.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 4
    ISSN: 0021-9304
    Schlagwort(e): femoral neck ; fracture ; osteosynthesis ; stability ; polylactide ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The initial stability of femoral neck osteosynthesis provided by three self-reinforced poly-L-lactide (SR-PLLA) or three metallic cannulated screws was compared. A standard transverse subcapital osteotomy was created with a hand saw in 19 pairs of human cadaver femora. Two fixation methods were randomly used in each pair. Fixations were exposed to a progressive cyclic loading test to determine the deflection curves, the ultimate load-carrying capacity, and the total amount of load absorbed. One pair served as a pilot and two nonoperated pairs served as controls. The positioning of the three fixation screws, whether one screw proximally and two screws distally or vice versa, provided equal stability. Metallic fixation proved to be more stable than SR-PLLA fixation as the average maximum load-carrying capacity was 3400N for the metallic and 2600N for the SR-PLLA fixation. However, SR-PLLA screws showed sufficient fixation properties for considering clinical trials in Garden I-II femoral neck fractures in well cooperative patients. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 171-175, 1998.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 5
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 200-206 
    ISSN: 0021-9304
    Schlagwort(e): cell culture ; flow cytometry ; cytoxicity assay ; scanning electron microscopy ; titanium-tantalum ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: To evaluate the biocompatibility of a new titanium-tantalum alloy, with qualities superior to titanium alone, for use in oral implantology, fibroblast and epithelial cell lines were grown on plastic, titanium, copper, and titanium-tantalum supports. Studies using scanning electron microscopy, flow cytometry, and cytotoxicity assays were conducted to compare the different supports. Scanning electron microscopic observations showed high densities of fibroblasts and epithelial cells with well-developed attachment systems in the form of cytoplasmic projections. Cell densities were lower on titanium and titanium-tantalum surfaces than on plastic. Cell numbers, as determined by cytotoxicity assays, were significantly higher on plastic than on titanium or titanium-tantalum surfaces while fibroblasts proliferated better than epithelial cells on both metal surfaces. Flow cytometric analyses of cell cycles did not reveal any significant variations in the distribution of cells among the cycle phases on the three materials. We found no differences with regard to the parameters studied between titanium and the titanium-tantalum alloy. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 200-206, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 6
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 215-221 
    ISSN: 0021-9304
    Schlagwort(e): bovine pericardium ; collagen fibers ; light scattering ; bioprostheses ; heart valves ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: In Part I of this work we used small-angle light scattering (SALS) to quantify the fiber architecture of 20 bovine pericardial sacs, along with corresponding tissue-thickness measurements, to determine optimal material selection sites. In order to determine the anatomic consistency of these sites, the fiber architecture and thickness data from all 20 sacs were averaged together using a cartographic analysis method that took advantage of the geometry of the prolate spheroid mold used to process the sacs. Optimal selection sites were determined based on a local criteria where all fiber preferred directions within a 2.54-cm circular area were within ±10°. The largest contiguous area (LCA) for the entire BP sac was 20.54 cm,2 located in the vicinity of the left ventricle of the heart. The LCA tissue thicknesses were also relatively uniform, further supporting the use of these areas. However, even within these optimal areas there was a ±20° standard deviation in local fiber preferred directions, resulting in at best a 40° spread in local preferred directions. The observed structural variability may be due to regionally heterogeneous physiologic loadings induced by the ligamentous attachments. These attachments may alter the regional fiber preferred orientation to support local mechanical loadings. Overall, given the inherent structural variability of the BP sac, we conclude that use of anatomic location alone will not consistently guarantee the selection of tissue specimens with a highly homogeneous and predictable fibrous structure. It is thus suggested that a direct fiber measurement presorting method be employed when selecting BP specimens for bioprosthetic applications where tissue structural homogeneity and uniformity is critical. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 215-221, 1998.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 7
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 9-15 
    ISSN: 0021-9304
    Schlagwort(e): fiber-optic pH sensor ; pH sensing membrane ; fluorescent probe ; SNAFL ; photo-crosslinking ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: A fiber-optic pH sensor was prepared using the self-referencing fluorescent pH probe carboxy seminaphthofluorescein (SNAFL-2). The ratio of the emission from the base form of this dye and the emission near the isoemissive point is insensitive to variations in the excitation intensity and photobleaching. The carboxy SNAFL-2 and a photoaffinity crosslinker, 4-azido-2,3,5,6-tetrafluorobenzoic acid, succinimidyl ester, were attached onto poly(acrylamide-co-vinylamine) to form a hydrophilic functional membrane for the fiber-optic sensor. Photo crosslinking was used to create a crosslinked pH-sensing membrane and covalently bind the membrane onto the surface of the PMMA optical fiber. The fluorescent properties of the membrane-fiber conjugate have been determined. The membrane is stable, and the pH sensor shows a fast response time and excellent resolution in a wide pH range of 3 to 11. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 9-15, 1998.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 8
    ISSN: 0021-9304
    Schlagwort(e): endothelial cells ; mesothelial cells ; cell seeding ; PTFE ; blood flow ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: An investigation was made into the effect of blood flow on endothelial cells (EC) and mesothelial cells (MC) seeded on a vascular expanded polytetrafluoroethylene (ePTFE) prosthesis coated with a fibroblastic matrix. Endothelial cells were obtained from the external jugular vein and MC from the omentum. To test the performance of prostheses, a custom designed, femoral “ex vivo” circuit was developed in mongrel dogs. Four study groups were established: a control group, A1, where prostheses were uncoated and seeded with EC; a second control group, A2, where prostheses were uncoated and seeded with MC; group B1 where prostheses were coated with a fibroblastic matrix and seeded with EC; and group B2 where coated prostheses were seeded with MC. All cells were labeled with 111Indium oxine (10 μCi/mL) before seeding. After the seeded cells had formed a monolayer on the ePTFE prostheses (which took approximately 24 h) the prostheses were placed in the “ex vivo” circuit. The rates of blood flow to which prostheses were exposed were measured at the point of inflow (117.5 ± 12.50 mL/min, mean ± SD) and outflow (72.6 ± 14.3 mL/min). MC showed a greater baseline radionuclide uptake than did EC. The cells of groups B1 and B2 adhered sufficiently to the fibroblastic matrix and covered enough of the prosthetic surface to be positioned in the “ex vivo” circuit (76.90 ± 8.24% surface covered in EC-seeded prostheses and 71.65 ± 6.23% in MC-seeded prostheses). After exposure to blood flow the quantity of radionuclide-labeled cells and the prosthetic surface covered by them were greatly reduced though the fibroblast-coated prostheses showed greater cell retention. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 32-39, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 9
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 61-70 
    ISSN: 0021-9304
    Schlagwort(e): immunoisolation of pancreatic islets by encapsulation ; polyelectrolyte complexation ; control of capsule permeability ; size exclusion chromatography ; protein A sepharose-antibody complex ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Transplantation of immunoisolated islets of Langerhans has been proposed as a promising approach to treating insulin-dependent diabetes mellitus. Recently, a cell delivery system based on a multicomponent microcapsule has been designed for the immunoisolation of insulin-secreting pancreatic islets. The capsule, formed by polyelectrolyte complexation of sodium alginate and cellulose sulfate with poly(methylene-co-guanidine), markedly has improved mechanical strength compared with the widely used alginate/poly(L-lysine) capsules. It also provides a flexibility for readily adjusting membrane thickness and capsule size, and, more important, the membrane permeability can be altered over a wide range of molecular sizes. To rigorously test the capsule diffusion properties, we have improved capsule permeability measurement by using two complementary methods: (1) size exclusion chromatography with dextran standards; and (2) newly developed methodology for assessing permeability to a series of biologically relevant proteins. Viability and function of rat pancreatic islets enclosed in the capsules with different permeability were tested in vitro. The insulin secretion of encapsulated islets was well preserved even though slightly delayed in comparison with a control group of free islets. We believe that the unique features of this encapsulation system together with the precise characterization of its physical parameters will enable us to find the optimal range of capsule permeability for in vitro and in vivo survival and function of encapsulated pancreatic islets. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 61-70, 1998.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 10
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 86-91 
    ISSN: 0021-9304
    Schlagwort(e): styrene-butadiene-styrene triblock copolymer ; dimethyl amino ethyl methacrylate ; graft copolymer ; heparin ; biomaterial ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The grafting of dimethyl amino ethyl methacrylate (DMAEMA) onto styrene-butadiene-styrene triblock copolymer (SBS) membrane was subsequently conducted by UV-radiation induced graft copolymerization without degassing to obtain the SBS-g-DMAEMA copolymer membrane. The substituted amino groups on the SBS-g-DMAEMA graft copolymer membrane were quaternized with iodomethane, and then the membrane was treated with heparin to prepare the heparin-containing SBS-g-DMAEMA copolymer membrane (SBS-g-DMAEMA-HEP). The graft copolymer membrane (SBS-g-DMAEMA) and the heparin-containing SBS-g-DMAEMA copolymer membrane (SBS-g-DMAEMA-HEP) were characterized by FTIR spectroscopy. The heparin content was determined by toluidine blue heparin assay. Contact angle, water content, and protein adsorption of fibrinogen and albumin experiments were also performed to evaluate the effect of graft amount and heparin content on the biocompatibility of SBS-g-DMAEMA and SBS-g-DMAEMA-HEP graft copolymer membranes. By using Kaelble's equation, the surface tension of SBS-g-DMAEMA and SBS-g-DMAEMA-HEP were determined. It was found that with increasing grafting amount and the heparin content, the surface tension and water content of SBS-g-DMAEMA membrane increased, whereas the contact angle decreased. The amount of the adsorption of albumin and fibrinogen decreased with increasing graft amount and heparin content. However, there was a minimum for adsorption of proteins in the SBS-g-DMAEMA and SBS-g-DMAEMA-HEP membranes. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 86-91, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 11
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 120-129 
    ISSN: 0021-9304
    Schlagwort(e): polyethylene (UHMWPE) ; implant retrieval ; total hip arthroplasty ; wear ; ultrasound ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: A new, in vitro ultrasound-based method to measure the thickness of acetabular polyethylene components was developed and applied to 26 uncomplicated autopsy-retrieved components and 40 unused components. The average age at total hip arthroplasty was 62 years and the average time in service of the retrieved components was 49 months. The clinical notes indicated that each of the arthroplasties was functioning well at the time of the patients death. Thickness distributions in the retrieved components had two distinct patterns. Eighteen of the retrieved components (69%) had their thinnest areas self-contained and located near the polar point. In the other 8 retrieved components (31%) the areas of minimum thickness were adjacent to the rim. Thickness distribution in the unused cups was predominately concentric with the thinnest area located near the polar point (85% of the cups). Detection limits for dimensional change were established based on the variability found in the unused liners. Fifteen of the 26 retrieved components (58%) had areas of reduced thickness which exceeded the detection limits; the average thickness reduction rate for these components was 0.076 mm per year. The other 11 retrieved components (42%) lacked such areas. The 15 cups with areas of reduced thickness had a longer time in service (63 ± 18 months) than the 11 cups without areas of reduced thickness (32 ± 25 months) (p = 0.003), but no other clinical factor (age, gender, Harris hip score, size and inclination of the cup, type of femoral fixation) was associated with these 15 cups. Cylindrical models to estimate volumetric change tended to underestimate the actual changes, suggesting that the actual particulate burden may be greater than previously appreciated.Finding that the pattern of thickness reduction can vary suggests that distinctive hip loading modes may be present postoperatively in patients with total hip arthroplasty. The wear rates of these components are consistent with wear rates calculated from radiographic data for well-functioning implants and are considerably lower than wear rates calculated for surgically-retrieved implants, indicating that autopsy-derived retrievals may be more representative of the majority of components currently in service than surgically-derived retrievals. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 120-129, 1998.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 12
    ISSN: 0021-9304
    Schlagwort(e): fluorapatite ; hydroxyapatite ; implant ; resorption ; stereology ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Resorption (defined as loss of ceramic coating because of cellular activity or dissolution) of ceramic coatings is a matter of concern for the long-term performance of ceramic-coated implants. A new fluorine-containing coating, fluorapatite (FA), has been shown to be more stable than hydroxyapatite (HA) in unloaded models. In a weight-bearing model in trabecular bone, we evaluated loss (defined as reduction of coating irrespective of type of mechanism) of HA and FA coatings during 25 weeks of implantation. Eight mature dogs had HA- or FA-coated implants inserted bilaterally into the weight-bearing region of the medial femoral condyle. Quantified loss of ceramic coating was estimated at the light microscopic level using stereological methods. The experiment showed significant loss of both types of coatings. However, no statistical difference in loss of ceramic coating was found regarding surface area, implant coverage, volume, and thickness (p = 0.77, p = 0.13, p = 0.56, p = 0.23, respectively). Completely resorbed HA coating was replaced by 36 ± 6.0% (range: 26-42) bone in direct contact with the implant surface compared with 29 ± 16.0% (range: 12-59) for FA (p = 0.40), suggesting that the implant was firmly fixed despite loss of the ceramic coating. Transmission electron microscopy in combination with electron energy spectroscopy and electron spectroscopic imaging showed that osteclast-like cells, osteocytes, macrophage-like cells, and fibroblasts had phagocytosed calcium-containing fragments, indicating cell-mediated resorption of the ceramic coating. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 141-152, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 13
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 40-51 
    ISSN: 0021-9304
    Schlagwort(e): polyethylene particles ; macrophages ; phagocytosis ; cytokines ; histology ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: In this study, an in vitro model has been developed to examine the interactions of macrophages with ultrahigh molecular-weight polyethylene (UHMWPE) and high-density polyethylene (HDPE) particles. Polyethylene particles are the major constituent of the material debris formed as a result of orthopedic implant wear. However, the study of polyethylene particle interactions with cells has been limited. UHMWPE (18-20 μm) and HDPE (4-10 μm) were suspended in soluble collagen type I and subsequently solidified on glass coverslips. The particle chemistry was characterized by Fourier transform infra-red spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Mouse cell line macrophages (IC-21) were established on the collagen-particle substrata and maintained for up to 24 h. The response of the cells to the particles was examined by light and transmission electron microscopy (LM and TEM), as well as by scanning electron microscopy (SEM), and compared to cells on control collagen surfaces without particles. Histological analysis of the samples revealed that the macrophages surrounded larger particles (18-20 μm) and the cells appeared to be attached to the surface of the particles, and the smaller particles (4-10 μm) had been phagocytosed within 2 h. Inflammatory cytokines (TNF-α, IL-1α, IL-1β, and IL-6), lysosomal enzymes (β-galactosidase and hexosaminidase), and prostaglandin E2 were released into the medium, and IL-1α, IL-1β, PGE2, β-galactosidase, and hexosaminidase levels were significantly increased over collagen control values. The results demonstrate active phagochemotaxis by macrophages for wear particulates and validate this model as a means of studying the specific in vitro interactions of polyethylene with cells. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 40-51, 1998.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 14
    ISSN: 0021-9304
    Schlagwort(e): PVDF ; differential scanning calorimetry ; X-ray scattering ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The outstanding biocompatibility of the polyvinylidene fluoride (PVDF) monofilament suture together with other desirable characteristics, such as ease of handling and resistance to biodegradation, makes it an attractive alternative monofilament suture material for cardiovascular surgery. However, to achieve a high performance suture, the polymeric raw material must be exposed to different treatments, which lead to different degrees and types of crystallization. Since these crystalline modifications deeply influence the mechanical characteristics and the biostability of the sutures, the authors hereby propose a method of quantifying the different structures of PVDF using wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The commercial devices are achieved by coloring and processing the polymeric raw material. The white and unprocessed 4-0 unswaged suture presents 19% of the α phase, 38% of the β structure, and no γ form. Coloration increases the amount of the β phase by 5-9% at the expense of the α phase. On the other hand, processing the fibers lead to the conversion of some of the amorphous phase to the γ structure, the importance of which is 6-7%. Finally, tensile measurements performed on the different PVDF fibers clearly proves that their mechanical characteristics depend on the presence of these crystalline forms in the polymeric structure of PVDF. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 184-189, 1998.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 15
    ISSN: 0021-9304
    Schlagwort(e): occlusive effects ; lactic acid-glycolic acid copolymer membrane ; expanded polytetrafluoroethylene membrane ; environmental scanning electron microscope ; gingival fibroblasts ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The cell occlusive effects on human gingival fibroblasts of degradable lactic acid-glycolic acid copolymer membranes (noncoated membranes) and membranes coated with a sucrose ester of fatty acid (coated membranes) were studied and compared with those of expanded polytetrafluoroethylene (e-PTFE) membranes. The membranes were immersed in a culture medium periodically for 21 days and interposed into a chemotaxis chamber, and the fibroblasts then were cultured in the chamber for another 7 days. The passage rate of cells through the membranes was calculated and the change in surface structure of each membrane after immersion for 28 days was observed by an environmental scanning electron microscope. The passage rate of coated membranes (3.4 ± 2.2%) was significantly lower than that of noncoated (25.7 ± 5.1%) at the 28th day whereas the passage rate of e-PTFE membranes was 0.8-1.5%. Many pores were observed on the noncoated membranes before immersion while the coating material covered most of the pores on the coated membranes. The average pore size of the noncoated membranes was larger than that of the coated membranes at day 28. The structure of the e-PTFE membranes underwent no change. The passage rate of the coated membranes was not different from the e-PTFE membranes, suggesting an effect that might be useful for a guided tissue regeneration procedure. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 554-559, 1998.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 16
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 580-587 
    ISSN: 0021-9304
    Schlagwort(e): plasma spraying ; hydroxyapatite ; decomposition ; vaporization ; amorphous ; X-ray diffraction ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Thermally processed hydroxyapatite coatings used on dental implants and hip prostheses for enhanced fixation may typically consist of a number of chemical and structural phases. These phases affect coating performance and tissue attachment. Hydroxyapatite was plasma sprayed to examine the phase evolution during processing. Coatings were examined with X-ray diffraction and elemental analysis. Results indicate that phase transformations are produced by (a) preferential removal of hydroxyl and phosphate leading to a change in melt composition, and (b) the high cooling rate due to the thermal spray process. Hydroxyl group removal promotes the amorphous phase and oxyapatite. Further heating produces a less viscous melt facilitating decomposition of hydroxyapatite to tricalcium and tetracalcium phosphate. Phosphate removal during flight produces a more calcium-rich melt preferring tetracalcium phosphate and calcium oxide formation. A proposed model shows the phase location within the lamellae of these coatings. Coating processes must thus prevent removal of hydroxide and phosphate during processing to maximize the hydroxyapatite content. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 580-587, 1998.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 17
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 244-251 
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Glass-reinforced HA composites were produced using phosphate-based glasses, and a structure refinement was carried out to determine the effect of the glass on the structure of the residual HA. Quantitative phase analysis showed that the glass causes some of the HA to decompose to β-TCP and, at higher temperatures, to α-TCP. It also was indicated that when three phases were present, the formation of the α-TCP arose from decomposition of the β-TCP and not from further decomposition of HA to α-TCP. The unit cell dimensions showed a decrease in the a axis and an increase in the c axis, giving an overall unit cell decrease in volume. There also was a significant effect based on the amount of glass added. The changes found in the composite containing the 4 wt % glass were attributed to the loss of carbonate and loss of hydroxyl. This was expected to cause shrinkage in the unit cell; however this was not seen, and therefore the major changes in the unit cell were attributed to the ions from the glass taking an interstitial role in the HA structure, thus not allowing the unit cell to shrink as much as expected. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 244-251, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 18
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 266-276 
    ISSN: 0021-9304
    Schlagwort(e): polyethylene glycol ; diacrylate ; peptide ; photopolymerization ; RGD ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Photopolymerized crosslinked networks of poly(ethylene glycol; PEG) diacrylate (MW 8000) were derivitized throughout their bulk with Arg-Gly-Asp (RGD)-containing peptide sequences. Incorporation was achieved by functionalizing the amine terminus of the peptide with an acrylate moiety, thereby enabling the adhesion peptide to copolymerize rapidly with the PEG diacrylate upon photoinitiation. PEG diacrylate hydrogels derivitized with RGD peptide at surface concentrations ranging from 0.001 to 1 pmol/cm were studied in vitro for their ability to promote spreading of human foreskin fibroblasts over 24 h. Hydrogels not derivitized with peptides were poor substrates for adhesion, permitting spreading of only 5% of the seeded cells. When immobilized with no spacer arm, both RGD and RDG (inactive control) supported spreading of ∼50% and ∼15% of cells at 1 and 0.1 pmol/cm2 surface concentrations, respectively; lower concentrations did not promote spreading. When a MW 3400 PEG spacer arm was incorporated between the hydrogel and the peptide linkage, incorporation of 1 pmol/cm RGD promoted 70% spreading whereas RDG at the same concentration did not promote spreading. In addition, when cells were seeded in serum-free medium, only RGD peptides incorporated with a spacer arm were able to promote spreading. Thus peptide incorporated into PEG 8000 diacrylate hydrogels without a spacer arm nonspecifically mediated cell spreading whereas incorporation via a MW 3400 PEG spacer arm was required to permit cell spreading to be specifically mediated. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 266-276, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 19
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 12-23 
    ISSN: 0021-9304
    Schlagwort(e): resin composite ; silane treatment ; mechanical properties ; water sorption ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: A series of microfilled resin composites were formulated by incrementally mixing either agglomerated 20 nm or unagglomerated 50 nm silica microfillers into monomers composed of diphenyloxymethacrylate and TEGDMA. The microfiller particles were prepared with and without a γ-methacryloxypropyl-trimethoxy silane coupling agent. Following polymerization, five material properties were tested: uniaxial tensile strength, Young's modulus in slow compression, Knoop hardness, water sorption, and toothbrush abrasion resistance. Results from these tests indicated that microfiller content clearly was the most influential parameter affecting material property performance. Composites containing 20 nm particles demonstrated greater water sorption, higher Knoop hardness, and better resistance to toothbrush wear. Surprisingly, the application of silane to microfiller surfaces did not greatly improve composite performance for most of the material properties tested in this study. However, water sorption behavior over a 3-year period was observed to be more stable for materials possessing silane-treated particles. Future evaluation of coupling agents should include long-term water storage prior to conducting mechanical tests. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40,12-23, 1998.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 20
    ISSN: 0021-9304
    Schlagwort(e): red cell substitute ; microcirculation ; hemoglobin ; liposome ; polyethyleneglycol ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Phospholipid vesicles encapsulating purified hemoglobin [Hb vesicles (HbV); diameter 259 ± 82 mm; oxygen affinity 31 mm Hg; [Hb] 5 and 10 g/dL] were developed to provide oxygen-carrying capacity to plasma expanders. Their function as a blood replacement was tested in the subcutaneous microvasculature of awake hamsters during severe hemodilution in which 80% of the red blood cell mass was substituted with suspensions of the vesicles in 5% human serum albumin (HSA) solution. Vesicles were tested with membranes that were unmodified (HbV/HSA) or conjugated with polyethyleneglycol (PEG) on the vesicular surface (PEG-HbV/HSA). The viscosity of 10 g/dL HbV/HSA was 8 cP at 358 s-1 owing to the intervesicular aggregation, while that of 10 g/dL PEG-HbV/HSA was 3.5 cP, since PEG chains inhibit aggregation. Both materials yielded normal mean arterial pressure, heart rate, and blood gas parameters at all levels of exchange, which could not be achieved with HSA alone. Subcutaneous microvascular studies showed that PEG-HbV/HSA significantly improved microhemodynamic conditions (flow rate, functional capillary density, vessel diameter, and oxygen tension) relative to unmodified HbV/HSA. Even though the enhancement of PEG modification did not achieve the functional characteristics of the blood-perfused microcirculation, PEG reduced vesicular aggregation and viscosity, improving microvascular perfusion relative to the unmodified type. These results highlight the significance of microvascular analysis in the design of red cell substitutes and the necessity of surface modification of HbV to prevent aggregation. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 66-78, 1998.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 21
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 104-114 
    ISSN: 0021-9304
    Schlagwort(e): HA ; particles ; dissolution ; macrophage ; osteolysis ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: It is controversial as to whether debris from hydroxyapatite (HA)-coated implants jeopardizes the long-term success of total joint replacements. It has been hypothesized that liberated HA particles are engulfed by macrophages and through normal cellular digestion prevent osteolysis and third-body wear. HA particulates, however, have been observed at the interface and on polyethylene articulating surfaces. There is limited data demonstrating the ability of HA to dissolve at the acidity levels associated with macrophage organelle digestion. The objective of this study was to determine if particulate HA could dissolve at the pH levels found in macrophage organelles. Characterized HA particles were placed into buffered solutions corresponding to phagosomal organelle pH levels: cytoplasmic (pH 7), phagosomal (pH 6), and lysosomal (pH 5). Flasks were under continuous agitation in a shaker chamber at 37°C. Calcium and phosphate ions were measured beyond the maximum life span of an activated macrophage. The data showed that calcium ions rose within the first 24 h and then remained constant throughout the experiment for all pH groups. Phosphate ion concentration showed a similar pattern at the lysosomal pH but remained undetected at the other organelle pH levels. The saturation point was highest at the lysosomal pH level and lowest at the cytoplasmic pH level. The results of this experiment leave the potential for HA particles to dissolve following macrophage digestion. However, caution must be exercised when interpreting the macrophage organelle digestion hypothesis; the size of the HA particle, the length of time required to completely dissolve the particle, and potential cellular toxicity all are factors that have yet to be determined before this hypothesis can be validated. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 104-114, 1998.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 22
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 145-152 
    ISSN: 0021-9304
    Schlagwort(e): bioactive bone cement ; Bis-GMA resin ; AW glass-ceramic ; mechanical properties ; bioactivity ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: We examined the influence of the proportion of glass-ceramic powder in a bioactive bone cement of our formula on the bone-bonding ability of cement. Changes in cement bonding with time also were examined. The bioactive bone cement consisted of MgO-CaO-SiO2-P2O5-CaF2 glass-ceramic powder (AW-GC powder) and bisphenol-α-glycidyl methacrylate (Bis-GMA)-based resin. AW-GC powder was added to the cement as 0%, 30%, 50%, 70%, and 80% w/w. Rectangular plates (2 × 10 × 15 mm) of each cement with polished surfaces were implanted into the proximal metaphysis of the tibiae of male rabbits, and the failure load was measured by detaching tests 10 and 25 weeks after implantation. The failure loads of each cement were 0% = 0.03, 30% = 1.52, 50% = 2.67, 70% = 3.56, and 80% = 5.59 kg at 10 weeks, and 0% = 0.05, 30% = 1.68, 50% = 2.77, 70% = 3.80, and 80% = 6.37 kg at 25 weeks. Observation of the cement-bone interface revealed that all bioactive bone cements (30%-80%) formed direct contact with bone whereas intervening fibrous tissue was observed in all specimens of the 0% group. By scanning electron microscopy, all bioactive bone cements (30%-80% groups) showed direct contact with bone at the cement-bone interface. In the 0% group, direct contact with bone at the cement-bone interface was not observed. By electron-probe microanalysis, a Ca-P-rich layer was not detected at the cement-bone interfaces of the 30%-70% bioactive bone cements, but in some samples of the 80% cement specimens a thin Ca-P-rich layer (3 μm thick) was observed at the interface at 10 and 25 weeks after implantation. These results show that all of the bioactive bone cements tested had the ability to bond to bone and to function as bioactive composites of ceramics and polymers. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 145-152, 1998.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 23
    ISSN: 0021-9304
    Schlagwort(e): basophils ; mast cells ; metal ions ; toxic histamine release ; apoptosis ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Recent data suggest that distinct metal ions can be released from dental alloys or other biomaterials, and may cause toxic effects on various cells. In this study, the effects of 14 metal ions on histamine release from human blood basophils (n = 4), isolated tissue mast cells (lung n = 8, uterus n = 2, skin n = 1, gingiva n = 1), the basophil cell line KU-812, and the mast cell line HMC-1 were analyzed. Of the 14 metal ions, Ag+ (0.33 mM) and Hg2+ (0.33 mM) were found to induce release of histamine in blood basophils, KU-812, mast cells, and HMC-1. The effects of Ag+ and Hg2+ were dose dependent and were observed within 60 min of incubation. In primary mast cells and basophils, Au3+ (0.33 mM) also induced histamine release, whereas no effects of Au3+ on HMC-1 or KU-812 cells were seen. The other metal ions showed no effects on primary or immortal cells within 60 min. However, Pt4+ (0.33 mM) induced histamine liberation in HMC-1 and lung mast cells after 12 h. The Ag+- and Hg2+-induced rapid release of histamine from HMC-1 was associated with ultrastructural signs of necrosis, but not apoptosis. In contrast, prolonged exposure to Pt4+ (0.33 mM, 14 h) induced apoptotic cell death in HMC-1 cells, as assessed by electron microscopy and DNA analysis. Together, certain metal ions induce distinct cytopathogenic effects in mast cells and basophils. Whereas Ag+, Hg2+, and Au3+ cause direct toxicity, Pt4+ causes cell death through induction of apoptosis. Whether such effects contribute to local adverse reactions to metal-containing biomaterials in vivo remains to be determined. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 560-567, 1998.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 24
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 588-593 
    ISSN: 0021-9304
    Schlagwort(e): polyepsiloncaprolactone nanocapsules ; indium oxine ; in vitro release kinetics ; esterases ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The main purpose of this study was to determine the influence of factors (pH, enzymes, etc.) chosen partially to mimic in vivo conditions on the release of a model drug, indium oxine, from polyepsiloncaprolactone (PCL) nanocapsules in vitro. A nanocapsule suspension, an emulsion (O/W), and a solution in olive oil were prepared in order to compare the release of a radioactive tracer, indium oxine, as a function of time by an in vitro dialysis method. Nanocapsules were prepared by interfacial deposition of PCL and characterized by particle size distribution (laser light scattering) and determination of the polymer molecular weight by gel permeation chromatography (GPC). The results of this study suggest that the partition coefficient between the acceptor medium and the olive oil is the major parameter governing the release of the isotope, at least in the absence of significant enzyme activity. The PCL wall of nanocapsules is a barrier that does not seem to retard the release of indium. The addition of porcine liver esterases accelerated the degradation of PCL. This study confirms that the release of a drug from nanocapsules may be very different depending on the in vivo location, that is, the administration site. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 588-593, 1998.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 25
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 611-620 
    ISSN: 0021-9304
    Schlagwort(e): transmission electron microscopy ; high voltage electron microscopy ; osteogenesis ; bone remodeling ; bone-implant interface ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: This report presents transmission electron and high voltage transmission electron microscopic observations of bone and associated remodeling tissues directly interfacing with endosteal dental implants. Undecalcified interfacial tissues were serially sectioned from mandibular samples encasing 60 implants placed into 30 dogs. Two-dimensional ultrastructural analyses and three-dimensional stereology showed that osteogenesis adjacent to dental implants is a dynamic interaction of osseous cells and a collagenous fiber matrix. This study showed that the interfacial bone consists of a mineralized collagen fiber matrix associated with an inorganic (hydroxylapatite) matrix. This study suggested that an unmineralized collagen fiber matrix initially is laid down directly at the implant surface, and that this matrix then is mineralized. Osteoblasts interacted with this matrix, eventually becoming encased within developing lacunae during the remodeling process. This process formed the cellular (osteocyte) aspects of the developed bone. Osteocyte processes extended through canaliculi directly to the implant surface. Apparently, these processes also were entrapped within canaliculi during the mineralization events. At times, these processes paralleled the implant surface. The bone-implant interfacial zone was primarily fibrillar (both mineralized and unmineralized) in morphology, with an electron-dense, ruthenium positive deposition. This electron-dense material was approximately 20 to 50 nanometers in thickness, and only this thin layer separated the remodeled mineralized bone from the implant. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 611-620, 1998.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 26
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 642-649 
    ISSN: 0021-9304
    Schlagwort(e): ureteral stent ; encrustation ; hydrogel ; Aquavene® ; silicone ; polyurethane ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The effective long-term use of indwelling ureteral stents is often hindered by the formation of encrusting deposits which may cause obstruction and blockage of the stent. Development of improved ureteral stent biomaterials capable of preventing or reducing encrustation is therefore particularly desirable. In this study, the suitability as a ureteral stent biomaterial of Aquavene®, a novel poly(ethylene oxide)/polyurethane composite hydrogel was compared with that of silicone and polyurethane, two materials widely employed in ureteral stent manufacture. Examination of Aquavene® in dry and hydrated states by confocal laser scanning microscopy, scanning electron microscopy, and atomic force microscopy showed the presence of numerous channels within a cellular matrix structure. The channel size increased considerably to as much as 10 μm in diameter in the hydrated state. Aquavene® provided superior resistance to encrustation and intraluminal blockage over a 24-week period in a simulated urine flow model. Unobstructed urine flow continued with Aquavene® at 24 weeks, whereas silicone and polyurethane stents became blocked with encrustation at 8 and 10 weeks, respectively. Weight loss within Aquavene® on the order of 9% (w/w) over the 24-week flow period indicates that extraction of the noncrosslinked poly(ethylene oxide) hydrogel may be responsible for the prevention of encrustation blockage of this biomaterial. In the dry state, Aquavene® was significantly harder than either silicone or polyurethane, as shown by Young's modulus, and rapidly became soft on hydration. These additional properties of Aquavene® would facilitate ease of stent insertion in the dry state past obstructions in the ureter and provide improved patient comfort on subsequent biomaterial hydration in situ. Aquavene® is a promising candidate for use in the urinary tract, as it is probable that effective long-term urine drainage would be maintained in vivo. Further evaluation of this novel biomaterial is therefore warranted. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 642-649, 1998.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 27
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 1-11 
    ISSN: 0021-9304
    Schlagwort(e): surface characteristics ; titanium implants ; osseointegration ; bone response ; loaded implants ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Many dental clinical implant studies have focused on the success of endosseous implants with a variety of surface characteristics. Most of the surface alterations have been aimed at achieving greater bone-to-implant contact as determined histometrically at the light microscopic level. A previous investigation in non-oral bone under short-term healing periods (3 and 6 weeks) indicated that a sandblasted and acid-etched titanium (SLA) implant had a greater bone-to-implant contact than did a comparably-shaped implant with a titanium plasma-sprayed (TPS) surface. In this canine mandible study, nonsubmerged implants with a SLA surface were compared to TPS-coated implants under loaded and nonloaded conditions for up to 15 months. Six foxhound dogs had 69 implants placed in an alternating pattern with six implants placed bilaterally in each dog. Gold crowns that mimicked the natural occlusion were fabricated for four dogs. Histometric analysis of bone contact with the implants was made for two dogs after 3 months of healing (unloaded group), 6 months of healing (3 months loaded), and after 15 months of healing (12 months loaded). The SLA implants had a significantly higher (p 〈 0.001) percentage of bone-to-implant contact than did the TPS implants after 3 months of healing (72.33 ± 7.16 versus 52.15 ± 9.19; mean ± SD). After 3 months of loading (6 months of healing) no significant difference was found between the SLA and TPS surfaced implants (68.21 ± 10.44 and 78.18 ± 6.81, respectively). After 12 months of loading (15 months of healing) the SLA implants had a significantly greater percentage (p 〈 0.001) of bone-to-implant contact than did the TPS implants (71.68 ± 6.64 and 58.88 ± 4.62, respectively). No qualitative differences in bone tissue were observed between the two groups of implants nor was there any difference between the implants at the clinical level. These results are consistent with earlier studies on SLA implants and suggest that this surface promotes greater osseous contact at earlier time points compared to TPS-coated implants. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 1-11, 1998.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 28
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 48-56 
    ISSN: 0021-9304
    Schlagwort(e): bioactive glass ; hydroxyapatite ; cell adhesion ; fibronectin ; protein conformation ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Bioactive glasses and ceramics enhance bone formation and bond directly to bone, and have emerged as promising substrates for bone tissue engineering applications. Bone bioactivity involves physicochemical surface reactions and cellular events, including cell attachment to adsorbed extracellular matrix proteins. The effects of fibronectin (Fn) adsorption and glass surface reaction stage on the attachment of osteoblast-like cells (ROS 17/2.8) to bioactive glass were analyzed. Bioactive glass disks were pretreated in a simulated physiologic solution to produce three reaction layers: unreacted glass (BG0), amorphous calcium phosphate (BG1d), and carbonated hydroxyapatite (BG7d). Synthetic hydroxyapatite (sHA) and nonreactive borosilicate glass (CG) were used as controls. A spinning disk device which applied a linear range of forces to attached cells while maintaining uniform chemical conditions at the interface was used to quantify cell adhesion. The number of adherent cells decreased in a sigmoidal fashion with applied force, and the resulting detachment profile provided measurements of adhesion strength. For the same amount of adsorbed Fn, cell adhesion was higher on surface-reacted bioactive glasses (BG1d and BG7d) than on BG0, CG, and sHA. For all substrates, cell attachment was primarily mediated by the RGD binding site of Fn, as demonstrated by blocking experiments with antibodies and RGD peptides. Cell adhesion strength increased linearly with adsorbed Fn surface density. Analysis of this fundamental relationship revealed that improved adhesion to reacted bioactive glasses resulted from enhanced cell receptor-Fn interactions, suggesting substrate-dependent conformational changes in the adsorbed Fn. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 48-56, 1998.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 29
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 86-91 
    ISSN: 0021-9304
    Schlagwort(e): X-ray diffraction ; ceramic ; external fixation ; coating ; biocompatibility ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The in vivo compatibility and degradation aspects of an innovative coating to be sprayed onto titanium implants were investigated. The surface of fluorinated apatite (fHA), consisting of fluorhydroxyapatite plasma sprayed in a vacuum atmosphere, was treated with carbonate to improve its biological compatibility. fHA coating was compared with titanium implants coated (a) with hydroxyapatite (HA) by the traditional plasma spraying, and (b) with titanium oxide (TiOx). Screw-shaped implants were inserted in the cortical bone of sheep tibiae. X-ray diffraction (XRD) analysis of bone tissue and coatings was carried out at 2, 4, 12 and 36 weeks after surgery. The crystallographic habit of the implant-facing bone, as well as the structural stability of the coating, were evaluated. For each time period and type of ceramic bone apatite lattice at the interface, no significantly different reference apatite lattice and no foreign peak were recorded. Two weeks after implantation, the bone at the interface was strongly unmineralized in all samples; after 4 weeks, poorly mineralized bone microareas decreased. At 12 weeks, the newly formed bone tissue at the interface with both the new coating and HA coating was shown to be fully mineralized; this crystallographic habit was retained at 36 weeks, when particle release from the tested material was lower compared to the controls. The XRD pattern of bone apatite surrounding the coating particles was unmodified. The innovative coating did not alter the mineralization process at the interface. It improved implant osteointegration, mainly due to a limited release of particles. Consequently, clinical performance of external fixation treatment could be improved by modifying the chemical composition of the implant surface. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 86-91, 1998.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 30
    ISSN: 0021-9304
    Schlagwort(e): methylmethacrylate ; polymethylmethacrylate ; free radicals ; polymerization ; redox polymerization ; bone cements ; in vitro study ; osteoblasts ; cytotoxicity ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Polymerization of orthopedic cements makes use of a peroxide initiator which is decomposed by an accelerator to provide free radicals. Free radicals which act on the monomer molecules are also known to induce cell lesions and cell death. We used an in vitro model of cement polymerization to study the effects of free radicals release on osteoblast-like cells. Initiation of methylmethacrylate was done with benzoyl peroxide and acceleration by N,N-dimethylaniline. Bulk polymerization was done in calibrated test tubes which were left aging until use. Polymers (aged from J1 to J31 days after completion of the polymerization process) were sawed to produce slices. Slices were rinsed in distilled water and free radical release was measured by spectrophotometric titration with p-iodonitrotetrazolium. Saos-2 osteoblast-like cells were cultured in parallel on the slices. Cells appeared to be round and were altered when grown on slices prepared freshly after polymerization. Cytomorphometric analysis of the cell shape surface area and form-factor polyethylene confirmed that they spread and flatten on slices prepared a long time after polymerization. Free radical release from polymethylmethacrylate cements is a long-lasting event that can induce bone cells alterations in their neighborhood. Two cytotoxic mechanisms were evidenced: (a) polymer slices released a stable toxic component which could be removed by extensive washing; (b) they released free radicals which were still detectable several days after the end of polymerization. The titration curve was a negative exponential. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 124-131, 1998.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 31
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 164-169 
    ISSN: 0021-9304
    Schlagwort(e): gingiva ; collagen ; polysaccharides ; heparin ; dextran ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Gingival fibroblasts are particularly involved in the physiologic maintenance and repair of periodontium. During these processes, cell proliferation and synthesis of a collagen-rich gingival matrix should be controlled. A dextran derivative, namely, carboxy methyl dextran benzylamide sulfonate (CMDBS), considered to be a functional analog of heparin, was previously described to regulate proliferation of different types of cells and independently to modulate the expression of collagen biosynthesis. In this report, we demonstrate that CMDBS and heparin inhibited gingival fibroblast proliferation. We then analyzed collagen biosynthesis by measuring the incorporation of the radiolabeled [3H]proline precursor into collagen by postconfluent gingival fibroblasts. Our results showed CMDBS did not alter total collagen synthesis; it induced the preferential accumulation of newly synthesized collagen into the pericellular matrix; and it decreased the expression of type III collagen, particularly in the cell layer. Taken together, our results suggest that by inhibiting cell proliferation, CMDBS could induce the synthesis of an extracellular collagenous matrix which forms a network between gingival fibroblasts. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 164-169, 1998.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 32
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 195-203 
    ISSN: 0021-9304
    Schlagwort(e): polyurethane ; phosphorylcholine ; protein adsorption ; phospholipid adsorption ; ellipsometry ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: In a previous report we demonstrated that the blood compatibility of poly(ether urethane) (PEU) was improved by grafting phosphorylcholine (PC) groups on the surface. The improved blood compatibility was indicated by decreased platelet adsorption/activation and reduced thrombin formation at the polymer surface in experiments in which the surfaces were contacted with platelet-rich plasma in vitro. In the present study, we investigated the effect of grafted PC groups at a PEU surface on protein and phospholipid adsorption. Adsorption of human fibrinogen (Fg), human serum albumin (Alb), human high-molecular-weight kininogen (HMWK), and dioleoyl phosphatidylcholine (DOPC) vesicles was measured by ellipsometry. For this purpose, thin PEU films were cast on silicon wafers. The polymer film was photochemically modified with a PC-containing aryl azide. The presence of PC groups on the polymer surface was demonstrated by ESCA (Electron Spectroscopy for Chemical Analysis). The hydrophilicity of the polymer surface increased by the surface modification, as indicated by a decrease of the contact angle from 59° before to 43° after modification. Our data show that the presence of PC groups has little effect on the adsorption of proteins to a PEU surface. The highest adsorption was observed for Fg (0.49 μg/cm2 on PC-modified PEU and 0.50 μg/cm2 on PEU), followed by HMWK (0.28 μg/cm2 on both PC-modified PEU and PEU), and Alb (0.16 μg/cm2 on PC-modified PEU and 0.18 μg/cm2 on PEU). Protein adsorption was further studied on a “biomembrane-like” DOPC bilayer formed on hydrophilic silicon. We found no protein adsorption on this DOPC bilayer. The adsorption of small unilamellar DOPC vesicles on the polymer surfaces amounted to about 0.06 μg/cm2 (corresponding to circa 30% of monolayer coverage) and was similar for PC-modified PEU and PEU. Despite this partial surface coverage, preadsorbed DOPC on the polymer surface diminished the subsequent adsorption of proteins considerably. These results show that the mere presence of phosphorylcholine groups on a PEU surface is insufficient to suppress protein adsorption. The highly ordered structure of natural phospholipid bilayers seems to be required to suppress protein adsorption effectively. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 195-203, 1998
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 33
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 115-123 
    ISSN: 0021-9304
    Schlagwort(e): entrapment ; islet ; reversible gel ; disulfide bond ; bioartificial pancreas ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Currently, there are three types of devices for a bioartificial pancreas; microencapsulation, an extravascular diffusion chamber, and an intravascular diffusion chamber. The purpose of the present study was to provide a new extracellular matrix hydrogel for the devices of extra- and intravascular diffusion chamber types. As the sol-gel transition of this hydrogel is reversible, refilling of islets in vivo will be possible without a severe traumatic procedure. The hydrogel was produced from a polyacrylamide derivative carrying thiol groups synthesized by radical copolymerization of acrylamide and N,N′-bis-acrylcystamine, followed by reduction of the disulfide bonds in the copolymer. This water-soluble copolymer was used to entrap hamster islets by re-formation of disulfide bonds on the copolymer to produce a hydrogel. The formed hydrogel was easily reliquefied by reduction of the disulfide crosslinks to thiols. Insulin release from the islet-entrapped hydrogel continued for more than 1 month when examined in vitro. A static glucose stimulation test for the entrapped islets exhibited an increased insulin release. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 115-123, 1998.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 34
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 180-186 
    ISSN: 0021-9304
    Schlagwort(e): chargeable functional groups ; gradient surfaces ; corona discharge ; surface grafting ; platelet adhesion ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Functional group gradients were prepared on low-density polyethylene (PE) sheets. The surface density of grafted functional groups was gradually changed along the sample length by way of corona discharge treatment with gradually increasing power following graft copolymerization of acrylic acid (AA), sodium p-styrene sulfonate (NaSS), or N,N-dimethyl aminopropyl acrylamide (DMAPAA). AA and NaSS are negatively chargeable and DMAPAA is positively chargeable in phosphate-buffered saline or plasma solution at pH 7.3-7.4. The prepared functional group gradient surfaces were characterized by measurement of the water contact angle, by electron spectroscopy for chemical analysis, and by Fourier transform infrared spectroscopy in the attenuated total reflectance mode. All these measurements indicated that the functional groups were grafted onto the PE surfaces with gradually increasing density. The platelets adhered to the functional group gradient surfaces along the sample length were counted and observed by scanning electron microscopy. It was observed that the platelet adhesion to the gradient surfaces decreased gradually with the increasing surface density of functional groups. This may be related to the hydrophilicity of the surfaces. The DMAPAA-grafted surface showed a large amount of platelet adhesion, probably due to its positive charge character, while the AA-grafted surface, which is charged negatively, showed poor platelet adhesion. However, the NaSS-grafted surface, which is also charged negatively, showed a relatively large amount of platelet adhesion. This may be associated with the existence of an aromatic ring close to the ionizable group in NaSS. It seems that surface functional groups and their charge character, as well as wettability, play important roles for platelet adhesion. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 180-186, 1998
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 35
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 204-213 
    ISSN: 0021-9304
    Schlagwort(e): growth hormone delivery ; bioactivity ; poly(∊-caprolactone); solvent casting; particulate leaching ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: We have characterized the biodegradable material poly(∊-caprolactone) (PCL) as a delivery system for recombinant human growth hormone (hGH). Two contrasting methods for the manufacture of the biomaterial were investigated: namely, solvent casting and solvent casting particulate leaching; the latter yielded porous PCL discs. The degree of porosity, which was assessed by scanning electron microscopy, could be controlled by incorporating selected concentrations of particulate sodium chloride during the manufacturing process. Bioactive hGH released from the PCL preparations was quantified with a highly sensitive and precise bioassay which was based upon hGH activation of rat lymphoma Nb2 cells. Eluates obtained from control discs of PCL which had not been loaded with hGH proved to be nontoxic when tested on these cells. The release of bioactive hGH from hormone-loaded nonporous discs of PCL was found to be a direct function of the initial hormone loading dose. Increased porosity of the discs manufactured by solvent casting particulate leaching increased the delivery of hGH from discs which had been immersion loaded. However, hGH release after surface loading was independent of porosity. Hormone concentrations were also assessed by immunoassay so that the ratios of bio- to immunoactivity (B:I ratio) of the hormone release could be determined. We found that the B:I ratio of the hormone after release from unstored discs was identical to that of the hormone prior to its incorporation into the PCL, demonstrating that the mild incorporation procedures utilized had not adversely affected the structural integrity of the hormone. However, if the hormone-loaded discs were stored at 37°C prior to elution, the B:I ratios of the hGH released decreased indicating that this compromised the bioactive site. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 204-213, 1998
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 36
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 314-323 
    ISSN: 0021-9304
    Schlagwort(e): polyethylene oxide (PEO) ; sulfonated PEO ; surface modification ; segmented polyurethane ; platelet adhesion ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Polyethylene oxide (PEO) surfaces were prepared by the addition of PEO- and sulfonated PEO-containing amphiphilic block copolymers as surface-modifying additives in a segmented polyurethane (PU). PEO-PPO-PEO triblock copolymers (Pluronics) with different PEO chain lengths (from 2 to 80) were used as additives. The prepared film surfaces were characterized by the measurement of dynamic water contact angles and electron spectroscopy for chemical analysis. It was observed that the PU films containing 10 wt % of PEO additives were surface-saturated with the additives regardless of their PEO chain length, but the PEO chains were more projected from the film surfaces containing the additives with longer PEO chains. The water absorption of the films increased largely with the increasing PEO chain length of the additives. The addition of PEO additives produced film surfaces that were in a gel-like state. The films demonstrated some extraction of the PEO additives. However, the additives with higher molecular weights were entrapped more stably into the PU matrix. The mechanical properties (tensile strength and elongation) of the films were changed by the addition of PEO additives, but the differences were not significant compared to the control PU. The platelet adhesion on the film surfaces decreased with increasing PEO chain length of the additives. The film surface containing additives with long PEO chains (chain length of 80) was particularly effective in preventing platelet adhesion. The effect of negatively charged sulfonate groups on the prevention of platelet adhesion appeared only on the film surfaces containing additives with short PEO chains. For longer PEO chains, the chain mobility effect was more dominant than the negative charge effect on the prevention of platelet adhesion. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 314-323, 1998.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 37
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 358-364 
    ISSN: 0021-9304
    Schlagwort(e): hydroxyapatite ; hydroxyl groups ; hexamethylene diisocyanate ; isocyanatoethyl methacrylate ; coupling agents ; surface modification ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The surface grafting reactions of a series of isocyanates with hydroxyapatite particles at different temperatures were studied by Infrared spectrophotometry (IR) and thermal gravimetric analysis (TGA). The study results show that both hexamethylene diisocyanate (HMDI) and isocyanatoethyl methacrylate (ICEM) react readily with HA while ethyl isocyanate acetate (EIA) and butyl isocyanate (BIC) have lower reactivity towards HA particles. It also has been found that the reaction of ICEM with HA follows a second-order reaction mechanism, despite the heterogeneous nature of the reaction, while the reaction of HMDI with HA does not due to the complexity of the reaction. Based on this study, it is concluded that ICEM and HMDI are suitable agents for the coupling of polymers due to their reactivity towards HA. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 358-364, 1998.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 38
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 378-384 
    ISSN: 0021-9304
    Schlagwort(e): UHMWPE ; plasma sterilization ; gamma sterilization ; structure ; fatigue ; wear ; gas sterilization ; low temperature sterilization ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The effects of gamma radiation and low temperature hydrogen peroxide gas plasma (HPGP) sterilization on structure and cyclic mechanical properties were examined for orthopedic grade ultra-high-molecular-weight polyethylene (UHMWPE) and compared to each other as well as to no sterilization (control). Density was monitored with a density gradient column and was found to be directly influenced by the sterilization method employed: Gamma radiation led to an increase, while plasma did not. Oxidation of the polymer was studied by observing changes in the carbonyl peak with Fourier transform infrared spectrometry and was found to be strongly affected by both gamma radiation and subsequent aging, while plasma sterilization had little effect. Gamma radiation resulted in embrittlement of the polymer and a decreased resistance to fatigue crack propagation. This mechanical degradation was a direct consequence of postradiation oxidation and molecular evolution of the polymer and was not observed in the plasma-sterilized polymer. Both gamma radiation and plasma sterilization led to improved wear performance of the UHMWPE compared to the nonsterile control material. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 378-384, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 39
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 414-418 
    ISSN: 0021-9304
    Schlagwort(e): lubrication ; cartilage ; lubricin ; wear ; hyaluronate ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Purified human umbilical hyaluronate and a commercial preparation of rooster comb hyaluronate (Healon®) intended for intra-articular viscosupplementation did not demonstrate the same degree of boundary-lubricating ability as bovine synovial fluid or its purified lubricating mucin, lubricin (p 〈 0.01). Boundary lubrication was measured in vitro in an arthrotripsometer oscillating natural latex against polished glass under a load of 0.35 MPa with an entraining velocity of 0.37 mm/s. The two hyaluronate solutions possessed the same hyaluronate concentration as synovial fluid, but Healon was 4.5 times more viscous. Present practice of viscosupplementation therapy for degenerative joint disease is limited and fails to implicate the important role of synovial mucin. Boundary lubrication provided by synovial mucin, independent of its viscosity, is not replicated by hyaluronate hydrogels. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 414-418, 1998.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 40
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 434-441 
    ISSN: 0021-9304
    Schlagwort(e): collagen ; bioprostheses ; glutaraldehyde ; calcification inhibitors ; serum conditioning ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The purpose of this study was to evaluate the effects of the calcification inhibitors FeCl3 and sodium dodecyl sulfate (SDS) on the morphology of glutaraldehyde-crosslinked type I collagen sponges and on their serum conditioning. Scanning electron microscopy (SEM) showed that the morphology of the sponges, already modified by glutaraldehyde crosslinking, underwent further changes after treatment of the hydrogels with inhibitors. Coral-like structures were found to branch from the bulk of the material especially in the case of SDS-treated samples. The composition and morphology of the conditioning layers was characterized after 48 h incubation in serum by SDS-polyacrylamide gel electrophoresis-immunoblot of the adsorbed proteins, by energy-dispersive X-ray analysis of the elements (EDX), and by SEM of the conditioned surfaces. All the samples showed the adsorption of proteins with molecular weights ranging from 10 to 203 kD. However, the peculiar adsorption of an approximately 10-kD band (complement C3 fragment) and of fibronectin were detected in the case of glutaraldehyde-crosslinked collagen. On the other hand, glutaraldehyde-crosslinked collagen treated with 0.1M FeCl3 showed the remarkable adsorption of a 29-kD band. The glutaraldehyde-crosslinked hydrogels showed the massive precipitation of crystals on their exposed surfaces, whereas a disordered network structure surrounding the collagen fibrils was found in the case of the samples pretreated with inhibitors. A predominant precipitation of sodium and chloride was detected in all the sponges, although the ratio between the peaks changed from from one hydrogel to another. The results reported in this article clearly indicate that the treatments with SDS and FeCl3 change the surface conditioning of collagen sponges, suggesting a possible role of deposited serum solutes in affecting mineralization processes on bioprosthesis. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 434-441, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 41
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 464-474 
    ISSN: 0021-9304
    Schlagwort(e): calcium phosphate coatings ; magnetron sputtering ; osteoblast ; in vitro ; bone ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: In previous studies we developed a RF magnetron sputter technique for the production of thin Ca-P coatings. With this technique coatings can be produced that vary in Ca/P ratio as well as in structural appearance. The aim of this investigation was to obtain more understanding of the biological behavior of these coatings by way of in vitro experiments. The effect of noncoated titanium (Ti) and three different Ca-P-sputtered surfaces on the proliferation and differentiation (morphology and matrix production) of osteoblast-like cells was studied. Proliferation was determined using counting procedures; morphology was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Fluorescent markers and energy-dispersive X-ray microanalysis (EDX) were used to obtain quantitative and compositional information about the resultant calcified extracellular matrix (ECM). Results demonstrated that proliferation of the osteoblast-like cells was significantly (p 〈 0.05) higher on noncoated than on Ca-P-coated samples. On the other hand, more mineralized ECM was formed on the coated surfaces. In addition, TEM confirmed that the cells on the coated substrates were surrounded by ECM with collagen fibers embedded in crystallized, needle-shaped structures. On the basis of these findings, we concluded that: (1) the investigated Ca-P sputter coatings possess the capacity to activate the differentiation and expression of osteogenic cells, and (2) bone formation proceeds faster on Ca-P surfaces than on Ti substrates. Further, this bone-inductive effect appeared to be dependent on the Ca-P ratio of the deposited coatings. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 464-474, 1998.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 42
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 475-489 
    ISSN: 0021-9304
    Schlagwort(e): human femur ; chimpanzee femur ; greyhound femur ; femur morphology ; total hip replacement ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The canine model remains an animal of choice for determining the efficacy and safety of various materials and designs used in human total hip replacement (THR). The primate also is used in orthopedic-related research for studying limb anatomy, gait, and age-related bone loss. In order to better understand the appropriateness of these animal models for human THR, external morphologies of thirty-three adult Caucasian human, sixteen adult chimpanzee, and forty-two adult greyhound femora were compared using osteometric methods. Measured parameters included anteversion angle, cervico-diaphyseal angle, femoral head offset in the frontal plane, and anterior bow profiles along the femoral diaphysis. Although some of the measured parameters were approximately similar between species (e.g., mean cervico-diaphyseal angle of humans and chimpanzees), the majority demonstrated morphologic differences that may be biomechanically significant for interpreting stress transfer across the hip (e.g., mean anteversion angle and mean normalized femoral head offset between species). Additionally, age-related changes in proximal femoral morphology and gait pattern, as well as species-related differences in local muscle and inertial forces, may result in notably different loading conditions across the hip joint of each species. Therefore, discretion must be exercised when evaluating canine or primate THR materials and designs for potential use in the human hip. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 475-489, 1998.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 43
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 520-529 
    ISSN: 0021-9304
    Schlagwort(e): 3D carbon/carbon composite ; collagen/apatite composite ; coating ; grafting ; phosphorylation ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: A three-dimensional carbon/carbon composite (3D C/C) was studied as potential bone-repairing material; its major mechanical properties were found to be closer to those of human bone than other common bone-repairing materials available. In vitro calcification tests revealed that as-received 3D C/C is almost bioinert in simulated body fluid (SBF) over an immersion period of 4 weeks. To improve the bioactivity of 3D C/C, surface modification was accomplished through two practical routes: (1) grafting with polyethylene glycol (PEG) and (2) phosphorylation and precalcification. After grafting with α, ω di(aminopropyl) polyethylene glycol 800 (NH2-PEG-NH2), a continuous layer of calcium phosphate was formed on the surface of 3D C/C in SBF after 4 weeks. Phosphorylated 3D C/C samples have the ability to induce apatite precipitation after precalcification in a saturated Ca(OH)2 solution for 1 week. To speed up the coating process, a calcification solution with collagen was developed in which a collagen/apatite coating layer can be formed on 3D C/C in 9 h in ambient conditions. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 520-529, 1998.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 44
    ISSN: 0021-9304
    Schlagwort(e): biphasic calcium phosphate ceramic ; monocyte ; lipopolysaccharides ; polymyxin B ; cell degradation ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Numerous cell types, such as monocytes and osteoclasts, are involved in calcified matrix degradation. In this context, calcium-phosphate ceramics present similar degradation processes in vivo and in vitro to those found in a natural calcified substrate. As the monocyte/macrophage lineage is among the first cells to appear in ceramic implantation sites, it is a key protagonist in inflammatory reaction and biodegradation mechanisms. This study investigated the ability of human monocytes/macrophages activated by various agents [lipopolysaccharides (LPS), polymyxin B (PMB)] to degrade biphasic calcium-phosphate ceramics. PMB sulfate is a bacteriostatic antibiotic that modulates LPS-induced cell activities in vivo and in vitro. Degradation pits (about 10 μm) produced on the pellet surface by these monocytes were discrete, with well defined margins. LPS increased the degradation of calcium-phosphate ceramic (number of lacunae, mean pellet surface area degraded) in a dose-dependent manner whereas polymyxin B downmodulated it significantly. The addition of 2 μg/mL of polymyxin B reduced the number of degradation lacunae and the extent of degraded surface area induced by 0.1 μg/mL LPS by 87% and 64%, respectively. Thus this cell culture system can be very useful in the study of cellular degradation of biomaterials and of the influence of therapeutic agents that may modulate these cell activities. © 1998 John Wiley & Sons, Inc. J. Biomed Mater Res, 40, 336-340, 1998
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 45
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 359-363 
    ISSN: 0021-9304
    Schlagwort(e): bone morphogenetic protein-2 ; hydroxyapatite ; osseointegration ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: To determine if recombinant human bone morphogenetic protein-2 (rhBMP-2) can be adsorbed onto porous ceramic hydroxyapatite (HA) and promote the integration of HA to host bone, 54 subperiosteal pockets were created on the skulls of 19 adult Pasteurella-free white rabbits. Fourteen HA implants were saturated with saline and placed in subperiosteal pockets (control), 22 HA implants were saturated with saline and placed into subperiosteal pockets after burring 1-2 mm of calvarium to expose bleeding cancellous bone, and 18 HA implants were saturated with rhBMP-2 and placed into subperiosteal pockets. The animals were sacrificed at 1 month with examination to determine implant mobility. Histology was used to determine the amount of bone growth into the implant. Of the 14 control sites, 10 implants were found to be freely mobile, five demonstrated host bone resorption, and only one exhibited bone growth into the implant. Of the 22 burred sites, eight were freely mobile and 10 demonstrated bone growth into the implant (p = 0.04). Of the 18 rhBMP-2 sites, only two were freely mobile, none demonstrated host bone resorption, and 16 exhibited bone growth into the implant (p = 0.00002). This study supports the use of porous ceramic HA as a biocompatible, osteoconductive implant material for use in craniomaxillofacial augmentation and reconstruction. It also provides evidence that rhBMP-2 enhances osseointegration, thereby fixing the implant in position against the host-bone interface. In the clinical setting, osseous fixation of the implant should aid in preventing displacement, minimizing host bone resorption, and decreasing the incidence of extrusion. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 359-363, 1998.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 46
    ISSN: 0021-9304
    Schlagwort(e): cartilage ; growth factors ; tissue engineering ; osteogenic protein-1 ; cartilage repair ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The objective of this study was to examine in vitro the influence of recombinant human osteogenic protein-1 [rhOP-1, or bone morphogenetic protein-7 (BMP-7)] on cartilage formation by human and goat perichondrium tissue containing progenitor cells with chondrogenic potential. Fragments of outer ear perichondrium tissue were embedded in clotting autologous blood to which rhOP-1 had been added or not added (controls), and the resulting explant was cultured for 3 weeks without further addition of rhOP-1. Cartilage formation was monitored biochemically by measuring [35S]-sulphate incorporation into proteoglycans and histologically by monitoring the presence of metachromatic matrix with cells in nests. The presence of rhOP-1 in the explant at the beginning of culture stimulated [35S]-sulphate incorporation into proteoglycans in a dose-dependent manner after 3 weeks of culture. Maximal stimulation was reached at 40 μg/mL (human explants: +148%; goat explants: +116%). Histology revealed that explants treated with 20-200 μg/mL of rhOP-1, but not untreated control explants, contained areas of metachromatic-staining matrix with chondrocytes in cell nests. It was concluded that rhOP-1 stimulates differentiation of cartilage from perichondrium tissue. The direct actions of rhOP-1 on perichondrium cells in the stimulation of chondrocytic differentiation and production of cartilage matrix in vitro provides a cellular mechanism for the induction of cartilage formation by rhOP-1 in vivo. Thus rhOP-1 may promote early steps in the cascade of events leading to cartilage formation and could prove to be an interesting factor in the regeneration of cartilage in articular cartilage defects. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 614-620, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 47
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 646-659 
    ISSN: 0021-9304
    Schlagwort(e): titanium ; surface treatment ; surface roughness ; surface composition ; surface energy ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Surgical implant finishing and sterilization procedures were investigated to determine surface characteristics of unalloyed titanium (Ti). All specimens initially were cleaned with phosphoric acid and divided into five groups for comparisons of different surface treatments (C = cleaned as above, no further treatment; CP = C and passivated in nitric acid; CPS = CP and dry-heat sterilized; CPSS = CPS and resterilized; CS = C and dry-heat sterilized). Auger (AES), X-ray photoelectron (XPS), and Raman spectroscopic methods were used to examine surface compositions. The surface oxides formed by all treatments primarily were TiO2, with some Ti2O3 and possibly TiO. Significant concentrations of carbonaceous substances also were observed. The cleaning procedure alone resulted in residual phosphorus, primarily as phosphate groups along with some hydrogen phosphates. A higher percentage of physisorbed water appeared to be associated with the phosphorus. Passivation (with HNO3) alone removed phosphorus from the surface; specimens sterilized without prior passivation showed the thickest oxide and phosphorus profiles, suggesting that passivation alters the oxide characteristics either directly by altering the oxide structure or indirectly by removing moieties that alter the oxide. Raman spectroscopy showed no crystalline order in the oxide. Carbon, oxygen, phosphorus, and nitrogen presence were found to correlate with previously determined surface energy. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 646-659, 1998.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 48
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 30-40 
    ISSN: 0021-9304
    Schlagwort(e): laminin-5 ; titanium alloy ; passivation ; epithelial cells ; attachment ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Enhancement of epithelial cell attachment to laminin-5-coated titanium alloy (Ti-6Al-4V) implant material was evaluated in vitro. Protein analysis showed that Ti-6Al-4V has a high affinity for laminin-5 and adsorbed significantly more laminin-5 than laminin-1. DNA analysis showed that laminin-5 enhanced attachment of normal human epidermal keratinocytes (NHEK) to Ti-6Al-4V significantly more than did laminin-1 or uncoated controls. The effect of passivation on laminin-5 adsorption and activity on Ti-6Al-4V also was evaluated. Passivation had no significant effect on the amount of protein adsorbed; however, AFM, ESCA, and ToF-SIMS analyses suggested that passivation affects the conformation of adsorbed laminin-5. Although laminin-5 coating significantly enhanced rapid attachment of epithelial cells to both passivated and unpassivated Ti-6Al-4V, surface area measurements showed that cells spread on laminin-5-coated passivated Ti-6Al-4V covered a significantly larger surface area than cells spread on laminin-5-coated unpassivated samples. TEM analysis showed that cells formed significantly more hemidesmosomes on the surface of laminin-5 coated passivated than on the surface of laminin-5 coated unpassivated titanium alloy. The enhancement of rapid cell attachment, spreading, and hemidesmosome assembly on laminin-5-coated passivated samples may reflect better integration between epithelial cells and titanium alloy and thus may be predictive of long-term implant stability. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 30-40, 1998.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 49
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 49-57 
    ISSN: 0021-9304
    Schlagwort(e): dextran derivatives ; CMDBS ; thrombin ; heparin cofactor II ; anticoagulant ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Carboxymethyl dextran benzylamide sulfonate/sulfates (CMDBS) are synthetic polysaccharides with anticoagulant activity. We synthesized eight different highly substituted CMDBS and one CMDSu. We studied both their anticoagulant activity and the catalysis of thrombin (T) inhibition by heparin cofactor II (HCII) and antithrombin (AT) in the presence of these dextran derivatives relative to heparin and dextran sulfate (DXSu). The anticoagulant activity of CMDBS was due both to direct thrombin inhibition and to catalysis of thrombin inhibition by HCII. The anticoagulant and catalytic activities of CMDBS were related mainly to their molecular weight and sulfate content. The interaction of the dextran derivatives with thrombin does not involve the active site of the enzyme. A kinetic study showed that all the CMDBS exhibited higher affinity for thrombin than heparin did but lower affinity than DXSu did, suggesting that the benzylamide and sulfate groups potentiate the interaction between the dextran derivatives and thrombin. This study shows that the mechanism by which the dextran derivatives inhibit thrombin is original and is related to preferential interaction with thrombin; this both inhibits the clotting activity of the enzyme and increases the reaction rate of thrombin inhibition by HCII. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 49-57, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 50
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 95-103 
    ISSN: 0021-9304
    Schlagwort(e): ToF SIMS ; XPS ; radiolabeling ; polystyrene and tissue culture polystyrene ; fibronectin ; protein adsorption, orientation, and conformation ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Protein adsorption is widely studied by a variety of techniques, but there still is little known about protein orientation and conformation after adsorption. This probably is due to the large number of parameters involved, such as the characteristics of the surface and the structure of the protein. In this study, the adsorption of fibronectin was investigated with three different techniques: radiolabeling, X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (ToF SIMS) on polystyrene and oxidized polystyrene. The first two techniques have been widely used to study protein adsorption, allowing us to determine the amount of protein adsorbed on each surface. The ToF SIMS, however, is a technique just emerging for the study of protein adsorption. This study confirms its utility since ToF SIMS is found to be sensitive to the protein orientation and/or conformation at the surface. Indeed, the ToF SIMS peaks characteristic of the protein show differences in their reduced intensity between the two substrates. These differences, which are not detected by XPS, are attributed to different orientations and/or conformations of the protein. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 95-103, 1998.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 51
    ISSN: 0021-9304
    Schlagwort(e): polypyrrole ; polyester ; conductivity ; in vitro ; cell culture ; cell activation ; interleukin expression ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Electrically conducting polypyrrole-treated films have recently been shown to influence the morphology and function of mammalian cells in vitro. This type of polymer represents a possible alternative biomaterial for use in vascular implantation. The present study compared the in vitro biocompatibility of five different polyester woven fabrics having increasing levels of electrical conductivity ranging from 4.5 × 104 to 123 Ω/square with that of low density polyethylene and polydimethylsiloxane primary reference materials. Biocompatibility was measured in terms of four different types of in vitro cellular response, including (a) an indirect and (b) a direct control organotypic culture assay using endothelial cells, (c) a polymorphonuclear (PMN) cell activation study using flow-cytometric measurements of CD11/CD18 integrin molecule expression, and (d) a semiquantification of interleukin (IL)-6 mRNA expression on monocytes/macrophages using reverse-transcriptase polymerase chain reaction. The organotypic culture study revealed that the fabrics with high levels of conductivity exhibited lower cell migration, proliferation, and viability. The PMN activation study of blood from 10 healthy adult donors demonstrated that the two most conductive fabrics were able to identify the more reactive donors. The levels of IL-6 mRNA expression by monocytes/macrophages decreased as the conductivity level of the fabrics increased. The results of the present study therefore indicate that high levels of conductivity (〈200 Ω/square) on polyester fabrics are detrimental to the growth, migration, and viability of endothelial cells; induce elevated PMN activation; and affect the intracellular metabolism of monocytes. They also point to a specific range of conductivity (103 〈 104 Ω/square) which is associated with an optimum in vitro cellular response. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 519-526, 1998.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 52
    ISSN: 0021-9304
    Schlagwort(e): transforming growth factor-beta1 (TGF-β1) ; wax-like polymer ; biodegradation ; biocompatibility ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The study reported describes an experimental biodegradable polymer ceramic composite with wax-like handling properties that was combined with 2.0 μg of recombinant human transforming growth factor beta (rhTGF-β1). The polymer/rhTGF-β1 combination was introduced into standard-sized calvarial defects in rabbits to evaluate biodegradability, biocompatibility, hemostasis control, and bone promotion. The experimental wound model was a standard-sized circular calvarial defect 8 mm in diameter. The experimental design included 24 skeletally mature New Zealand white rabbits divided evenly between two time periods (6 and 12 weeks) and among three experimental treatments (untreated defects and defects treated with polymer with or without rhTGF-β1). Evaluations consisted of clinical examinations, standardized radiography, radiomorphometry, as well as histology and histomorphometry. Data were analyzed by an Analysis of Variance (ANOVA) and Fisher's Protected Least Significant Difference test at each time period (level of significance p≤ 0.05). Radiomorphometry data indicated that standard-sized defects treated with the wax-like polymer alone and the polymer plus 2.0 μg of TGF-β1 were significantly more radiopaque than control sites at both 6 and 12 weeks. Histomorphometric data revealed the amount of new bone was significantly greater at 6 weeks in the polymer plus 2.0 μg of TGF-β1 and in the control group than in the polymer alone. Moreover, at 12 weeks, there was significantly more new bone in the control than in either the polymer alone or the polymer plus 2.0 μg of TGF-β1. We speculate the incomplete biodegradation of the polymer ceramic composite contributed to the radiopacity and may have retarded osseous regeneration. It is important that the bone wax-like polymer material was biocompatible and acted as a hemostatic agent. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 584-592, 1998.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 53
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 624-632 
    ISSN: 0021-9304
    Schlagwort(e): calcium phosphate coatings ; interface strength ; RF magnetron sputter deposition ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: In previous studies, an RF magnetron sputter technique was developed for the production of thin calcium phosphate coatings. Several deposition parameters were found to influence the growth rate and the stoichiometry of the coatings. For instance, deposition with additional oxygen pressure decreased the Ca to P ratio of the coatings to 1.67. For application of these coatings on actual Ti implants, it is important to know their adhesive tensile strength with the implant surface and how it varies with the deposition parameters. Motivated by these goals, the aim of this study was to measure the adhesive tensile strength of these coatings with Ti substrates and to study its variation with the deposition parameters. Since most mechanical characterization methods are incapable of providing a direct measure of the interface's fundamental strength, a novel laser spallation experiment was used to accomplish this task. In this experiment, a compressive stress pulse is generated on the back side of a substrate by impinging a 3-ns long Nd:YAG laser pulse. The stress pulse propagates through the substrate and is reflected into a tensile stress wave from the free surface of the coating deposited on its front surface. The returning tensile pulse pries off the coating if its amplitude is high enough. The peak interface tensile stress is computed by using the optically recorded free surface displacement of the coating. Because interface decohesion is accomplished at a strain rate of almost 107 s-1, all inelastic processes essentially are suppressed and the measured value essentially is the intrinsic tensile strength of the interface. Tensile strength values in the range of 500-900 MPa were recorded for the interfaces between sputter-deposited calcium-phosphate coatings and Ti substrates. To confirm the locus of failure, the spalled spots were examined using SEM and EDS. The variation in the measured values was related to the changes in the deposition conditions. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 624-632, 1998.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 54
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 657-670 
    ISSN: 0021-9304
    Schlagwort(e): platelets ; prothrombinase ; adherent ; biomaterials ; thrombin ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Platelet adhesion to biomaterials is often used as an index of blood compatibility, but a more clinically relevant issue is whether the adherent platelets are able to promote clot formation (i.e., if they are in the procoagulant state). Platelets rapidly generate thrombin when they are in the procoagulant state and the Va/Xa complex is present. We found that adherent platelets are procoagulant by three different methods: binding of FITC-Annexin V, acceleration of thrombin generation in the presence of Xa, Va, and prothrombin; and clotting of recalcified plasma. In the clotting time studies, the effect of adherent platelets on TCPS was completely eliminated by the addition of Annexin V, which is known to bind tightly to procoagulant platelets. The degree of procoagulant activity of adherent platelets was determined by measuring thrombin generation rates in the presence of the clotting factors Va, Xa, and prothrombin and normalizing to the number of adherent platelets. Two key observations were made in these studies. First, the procoagulant activity of platelets adherent to untreated and to several types of treated polystyrenes, as well as to glass and PET, was much greater than the procoagulant activity of unstimulated bulk phase platelets. Little difference in the procoagulant activity of adherent platelets was observed among the materials tested, however. Second, the procoagulant activity of platelets prestimulated with ionophore and subsequently allowed to adhere to Plastek® M was much greater than when adherent platelets were stimulated by the adhesion event only. Measured values for platelet adhesion, platelet activation, and contact activation of blood plasma are discussed in the context of their potential combined impact on blood clotting. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 657-670, 1998.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 55
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 104-110 
    ISSN: 0021-9304
    Schlagwort(e): bone morphogenetic protein ; osteoblasts ; microspheres ; poly(d,l lactide-co-glycolide) ; cellular responses ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Porous 50:50 poly(d,l lactide-co-glycolide) microspheres containing varying amounts of “free” recombinant human bone morphogenetic protein-2 (rhBMP-2) were evaluated for their ability to induce/enhance expression of osteoblastic characteristics by pluripotent mesenchymal cells in vitro. “Free” protein (Fp) is defined as protein present on the surface and within the porous matrix of the microspheres. Four preparations of bioerodible particles (BEP) were used: blank - without rhBMP-2; low Fp - 24 μg of free rhBMP-2 per g of particles; medium Fp - 403 μg/g; and high Fp - 884 μg/g. C3H10T1/2 cells (C3H) and bone marrow stromal cells (BMC) were cultured with 1 mg of BEP for up to 4 weeks, and cell growth and expression of osteogenic responses were determined weekly. For both cell types, control cultures (neither BEP nor rhBMP-2) and cultures with blank BEP exhibited no or minimal osteoblastic characteristics. Compared to control and blank BEP cultures, C3H cells responded to particles having medium and high amounts of free rhBMP-2 with increased cell growth and alkaline phosphatase activity, but osteocalcin secretion and mineralization were not markedly influenced. Low Fp BEP enhanced only the alkaline phosphatase activity of C3H cells. In contrast, although growth was not affected, rhBMP-2-loaded BEP increased alkaline phosphatase activity, osteocalcin secretion, and mineralization in BMC cultures in a dose-dependent manner (i.e., blank 〈 low 〈 medium 〈 high Fp). © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 104-110, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 56
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 398-404 
    ISSN: 0021-9304
    Schlagwort(e): feldspar glass ; crystallization ; cubic leucite, microstructure ; X-ray diffraction ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Previous studies have shown that the crystallization of glasses in the system K2O-Al2O3-SiO2, in the primary field of leucite, is not possible without modification of the composition. Leucite (KAlSi2O6) is used as a reinforcing phase in some compositions for all-ceramic dental restorations. However, because of their higher coefficient of thermal expansion, these materials cannot be veneered with conventional metal-ceramic porcelains. The purposes of this study were to investigate the crystallization behavior of a glass in the system K2O-Al2O3-SiO2 and to evaluate the effect of heat treatment on the crystal size, percent crystallinity, and coefficient of thermal expansion of the material. Ion-exchanged glass powder was prepared by mixing the glass with rubidium nitrate and heat-treating at 450°C for 4, 8, 24, or 48 h. Bars were made from these powders and baked under vacuum at 1038°C for 2 min. The bars made from the powder ion-exchanged for 48 h were further heat-treated for 4 h at either 800°C, 850°C, 900°C, 950°C, or 1038°C. X-ray diffraction analyses showed cubic leucite was the only crystalline phase in the specimens made from the powders ion-exchanged for 4, 8, 24, or 48 h and baked at 1038°C for 2 min. Further heat treatment for 4 h at either 800°C, 850°C, 900°C, 950°C, or 1038°C promoted the growth of cubic leucite. In addition, a second phase identified as tetragonal rubidium-leucite was present in the specimens heat-treated for 4 h at 1038°C. SEM observations showed that all specimens made from the powders ion-exchanged for 48 h exhibited small spherical crystals dispersed in a glassy matrix. The percent crystallinity ranged from 18.9% to 42.9% and the average particle size was between 0.64 to 1.18 μm. The coefficients of thermal expansion ranged between 8.076 and 8.788 × 10-6/°C. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 398-404, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 57
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 167-170 
    ISSN: 0021-9304
    Schlagwort(e): FT-IR ; microspectroscopy ; infrared ; injectable biomaterial ; calcium phosphate ; bone substitute ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Hydroxypropylmethylcellulose (HPMC) of high-viscosity grade is used as a ligand for a bioactive calcium phosphate ceramic (the filler) in a ready-to-use injectable sterilized biomaterial for bone and dental surgery. Application of physico-chemical methods such as XPS, NMR, or Raman spectroscopy encounters difficulties when used to study such a multiphased material. This paper reports on the application of FT-IR microspectroscopy (FT-IRM) for the investigation of inorganic and organic phases of the rough composite and separated phases obtained by mechanical or chemical extraction methods. A comparison of FT-IRM with the conventional KBr pellet method was made and indicates that the macro and micro FT-IR methods are complementary: the former revealed new chemical groups not visualized with the KBr method whereas the latter detected the major compound of the blend. FT-IR microspectroscopy was revealed to be a powerful method of analysis that is complementary to other existing spectroscopic methods. Moreover, it is expected to be a useful tool in the study of biomaterials in biological samples. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 167-170, 1998.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 58
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 468-473 
    ISSN: 0021-9304
    Schlagwort(e): macrophages ; cobalt chromium ; bone resorption ; cytokines ; aseptic loosening ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The purpose of this study was to elucidate the mechanisms by which cobalt chromium particulate wear debris contribute to the aseptic loosening of total joint prostheses. Incubation of macrophages with cobalt chromium led to release of tumor necrosis factor-α (TNF-α) and prostaglandin E2 (PGE2), but did not lead to release of interleukin-1β (IL-1β) or interleukin 6 (IL-6). Exposure of macrophages cocultured with osteoblasts to cobalt chromium also led to significant release of TNF-α and PGE2, but did not lead to significant IL-6 or IL-1β production. The release of PGE2 in the coculture system was greater than that detected when macrophages were exposed to cobalt chromium without the osteoblast contribution. Exposure of radiolabeled calvaria to media from macrophages incubated with cobalt chromium in coculture with osteoblasts led to release of 45Ca. In contrast, exposure of radiolabeled calvaria to media from isolated macrophages incubated with these particles did not result in release of 45Ca. Exposure of macrophages to cobalt chromium was toxic, as reflected by release of the intracellular enzyme lactate dehydrogenase. Macrophages play a role in the initiation of bone resorption at the interface through the phagocytosis of cobalt chromium particles and subsequent release of TNF-α and PGE2. The presence of osteoblasts at the interface may be required for amplification of the inflammatory response and ultimately for bone resorption. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 468-473, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 59
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998) 
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 60
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 541-548 
    ISSN: 0021-9304
    Schlagwort(e): apatite ; chitin ; in situ precipitation ; hydroxyapatite ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Composites of chitin with calcium phosphate were obtained by in situ precipitation of the mineral from a supersaturated solution onto chitin scaffolds. The chitin scaffolds were obtained by freeze drying to give a highly porous structure possessing a polar surface favorable for apatite nucleation and growth. The extent and arrangement of calcium phosphate deposits on the chitin and substituted chitin scaffolds were explored. Up to 55% by mass of calcium phosphate could be incorporated into chitin scaffolds. Deposits on the chitin surface were of a continuous apatite carpet nature while deposits on carboxymethylated chitin surfaces displayed a spherical morphology. Carboxymethylation of chitin exerts an overall inhibitory effect towards calcium phosphate deposition, but it provides for site-specific nucleation of the mineral phase. In situ precipitation can be an important route in the future production of various polymer-calcium phosphate composites. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 541-548, 1998.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 61
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 549-559 
    ISSN: 0021-9304
    Schlagwort(e): photopultrusion ; composites ; fiber-reinforced polymers ; photopolymerization ; methacrylates ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: To develop a dual-curing monomer system for the photopultrusion of reformable (soft) composites, a microhardness assay showed that in a blend with 2,2-Bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl] propane (Bis-GMA), the substitution of methyl methacrylate (MMA) for triethylene glycol dimethacrylate (TEGDMA) delayed the onset of gelation during photopolymerization. Adding lauroyl peroxide permitted the completion of polymerization thermally. This system was used to form silicate-glass-fiber-reinforced composites, with varying degrees of conversion, by photopultruding over a range of pulling speeds. Sol-gel extractions demonstrated both fully soluble and insoluble matrices. For the soluble material, gel permeation chromatography elucidated a trimodal distribution of molecular weights that corresponded to MMA, Bis-GMA, and polymeric molecules with molecular weights in the tens of thousands. Composites with matrix solubilities above about 10% wt could be swaged after photopultrusion to change the cross section from circular to rectangular before thermal processing. The effect on the final elastic modulus was small (∼44GPa, as measured in flexure for 57% vol-reinforced composites); but the final flexure strength was reduced by approximately 25% to a constant of about 1.2 GPa. Morphological characteristics that were seen in the circular-sectioned precursors were observed in the swaged rectangular products as well, including flaws when swaging was conducted at matrix solubilities above about 75%. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 549-559, 1998.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 62
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 593-599 
    ISSN: 0021-9304
    Schlagwort(e): collagen membrane ; collagen sponge ; adhesion ; Pseudomonas aeruginosa ; amikacin ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The adherence of P. aeruginosa to collagen membrane, sponge, and to a new anti-infective COLL dressing and the susceptibility of the organisms attached to the biomaterials to amikacin were investigated in vitro. After 17 h of attachment, the bacteria demonstrated an increased resistance to amikacin compared with their free-floating counterparts. Amikacin, even at a concentration exceeding 150 times the minimal bactericidal concentration (MBC) for the strain tested, did not eradicate the attached bacteria from the surface of collagen membrane. However, when the drug at a high concentration (over 16 times the minimal inhibitory concentration, MIC) was present in the incubation medium before it had been inoculated with P. aeruginosa, a reduction of 2 log10 units in the organisms adherent to the surface of collagen membrane was observed. We conclude that slow release of the antibiotic from the COLL dressing could control the bacterial colonization on the surface. In fact, the released amikacin at the final concentration of 32 times the MBC reduced the number of adherent bacteria by 6 log10 units. In contrast, ciprofloxacin at the same final bactericidal concentration completely eradicated the bacteria from the surface of COLL dressing. However, as ciprofloxacin is not recommended for use as a topical antimicrobial agent, a further search is needed to find an agent with a similar anticolonization activity. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 593-599, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 63
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 574-583 
    ISSN: 0021-9304
    Schlagwort(e): artificial implants ; calcium phosphates ; titanium ; osteointegration ; arthroplasty ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The early healing phase of hard tissue implants is important to their long-term success. Problems during this phase can result in a so-called primary biological failure. In 24 New Zealand white rabbits, the healing in cortical bone of noncoated TiAlV and cpTi cylinders and of TiAlV cylinders plasma-spray-coated with hydroxyapatite (HA) or fluorapatite (FA) was investigated histologically and histomorphometrically after 3, 7, 14, and 28 days. Histomorphometry consisted of bone contact measurements and the use of a new semi quantitative scoring system that discriminated various tissues in contact with the implant. The results demonstrated that the most important parameter in initial implant healing is the bone itself and not the characteristic of the implanted material. For all implants, healing was characterized by a sequence of hematoma formation, bone resorption, and new bone formation where the initial press-fit situation revealed more bone-implant contact than after 7 and 14 days. There were only minor differences between the implant types: the new bone formation directly on the implant surface was qualitatively histologically superior to the CaP-coated implants, but this could be confirmed with the scoring method only for the HA-coated implants. It is concluded that initial press-fit fixation in cortical bone is not an end situation; rather, what happens is that as a result of interface remodeling, early postoperatively implant integration in the bone will decrease temporarily prior to a subsequent phase of new bone formation. © 1998 John Wiley & Sons, Inc. J. Biomed Mater Res, 41, 574-583, 1998.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 64
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998) 
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 65
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 45-54 
    ISSN: 0021-9304
    Schlagwort(e): nanospheres ; polylactic acid-polyethylene glycol ; protein encapsulation ; protein delivery ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The development of injectable nanoparticulate “stealth” carriers for protein delivery is a major challenge. We have shown the possibility of entrapping human serum albumin (HSA) in polyethylene glycol (PEG)-coated monodisperse biodegradable nanospheres with a mean diameter of about 200 nm, prepared from amphiphilic diblock PEG-polylactic acid (PLA) copolymers, with loadings up to 9% (w/w). Microscopic techniques and surface analysis studies enabled us to prove that the protein was well entrapped and not adsorbed onto the particle surface. Zeta potential and water uptake studies corroborated that part of the PEG chains are located in the nanosphere matrix. Water uptake in the nanospheres was related to their chemical composition, i.e., the respective wt% of PEG and PLA in the matrix, and not on their fabrication procedure. The hydrophilic PEG blocks absorbed up to 130% (w/w) water, whereas PLA absorbed only about 10% (w/w). However, the rate of swelling at the beginning of the process was related to the structure of the matrix, more particularly to the manner in which PEG was disposed at the surface. Furthermore, it was shown that the PEG “brush” at the nanosphere surface drastically reduces HSA adsorption on the PEG-PLA nanospheres compared to the PLA ones. © 1998 John Wiley & Sons, Inc. J. Biomed Mater Res, 42, 45-54, 1998.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 66
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 422-430 
    ISSN: 0021-9304
    Schlagwort(e): cell attachment ; cell spreading ; silane chemistry ; model surfaces ; cytoskeletal organization ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Understanding the relationships between material surface properties, adsorbed proteins, and cellular responses is essential to designing optimal material surfaces for implantation and tissue engineering. In this study, we have prepared model surfaces with different functional groups to provide a range of surface wettability and charge. The cellular responses of attachment, spreading, and cytoskeletal organization have been studied following preadsorption of these surfaces with dilute serum, specific serum proteins, and individual components of the extracellular matrix. When preadsorbed with dilute serum, cell attachment, spreading, and cytoskeletal organization were significantly greater on hydrophilic surfaces relative to hydrophobic surfaces. Among the hydrophilic surfaces, differences in charge and wettability influenced cell attachment but not cell area, shape, or cytoskeletal organization. Moderately hydrophilic surfaces (20-40 degree water contact angle) promoted the highest levels of cell attachment. Preadsorption of the model surfaces with bovine serum albumin (BSA) resulted in a pattern of cell attachment very similar to that observed following preadsorption with dilute serum, suggesting an important role for BSA in regulating cell attachment to biomaterials exposed to complex biological media. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 422-430, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 67
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 461-467 
    ISSN: 0021-9304
    Schlagwort(e): microencapsulation ; diabetes ; atomic force microscopy ; surface characterization ; immunoisolation device ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The surface morphology of the microcapsule used as a bioartificial pancreas was examined by atomic force microscopy (AFM) under ambient conditions in a liquid environment. The standard contact mode was used for imaging. The capsules exhibited different morphologies and surface roughness depending on the composition of the cation solution: namely, the mole ratio of antigelling and gelling cations [Na+]/[Ca2+]. Surface roughness parameters obtained by AFM measurements provide quantitative information on the surface properties of the capsular membrane. In this respect, AFM can be considered a valuable technique complementary to optical microscopy in providing feedback for capsule optimization. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 461-467, 1998.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 68
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 633-648 
    ISSN: 0021-9304
    Schlagwort(e): segmented polyetherurethane (SPEU) ; hemolysis ; cytotoxicity ; cell culture ; blood compatibility ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Segmented polyetherurethane (SPEU) materials based on polytetramethylene oxide (PTMO, Mw 1000 and 2000) with various hard-segment contents were synthesized and their biocompatibilities studied via different tests. The static contact angle data reveal that the higher hard-segment-content SPEU material possesses a lower contact angle, implying that the surface of the higher hard-segment-content SPEU is more hydrophilic than its low hard-segment-content SPEU counterpart. The catalyst- and additive-free PTMO-based SPEU materials in this study possess neither a hemolytic nor a cytotoxic response that could be considered non toxic for biomedical applications. By using L-929 cell lines, a cell-seeding test indicated that the higher hard-segment-content SPEU material possesses quicker cell attachment and proliferation behaviors. In vitro platelet adhesion tests indicated that the lower hard-segment-content SPEU possesses less platelet adhesion than the high hard-segment-content SPEU material. Both ex vivo canine artery-artery (A-A) and arterio-venous (A-V) shunting tests revealed that the extent of platelet adhesion reaction is less for lower hard-segment-content SPEU. In addition, the blood compatibility of SPEU material synthesized from PTMO 1000 excels over PTMO 2000 SPEU material by nearly the same levels as the hard-segment-content SPEU. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 633-648, 1998.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 69
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 6-12 
    ISSN: 0021-9304
    Schlagwort(e): composite ; ligaments ; viscoelasticity ; mechanical properties ; hydrogels ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Despite the compelling need for artificial connective tissue replacements for orthopedic applications, to date, there is no material which can adequately reproduce the mechanical behavior of natural tissue with necessary long-term endurance. In this work, we introduce a novel soft composite material as a more suitable candidate for connective tissue replacement. The material proposed is based on a hydrogel-polymer matrix reinforced with poly(ethylene terephthalate) fibers wound helically to mimic the architecture of the collagen fibers in natural tissue. Macroscopic behaviors such as static stress-strain, stress relaxation, and dynamic frequency responses can be modulated with choice of the components and design of the composite structure. In doing so, the mechanical characteristics of natural ligaments can be qualitatively reproduced and sustained over time. © 1998 John Wiley & Sons, Inc. J. Biomed Mater Res, 42, 6-12, 1998.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 70
    ISSN: 0021-9304
    Schlagwort(e): dentin ; demineralization ; shrinkage ; rehydration ; atomic force microscopy ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Most current dentin bonding procedures use acid etchants to partially demineralize the dentin structure and provide pathways for resin infiltration. This study determined the recession rates of peritubular dentin and intertubular dentin as a function of pH during demineralization in citric acid solutions (0.0005-2.5M) and the effects of dehydration and rehydration on the partially demineralized dentin. Polished dentin disks were prepared with an internal reference layer and were studied at specific intervals for citric acid etching between pH 1 and 3.4 in an atomic force microscope. Peritubular dentin etched rapidly and linearly with time until it could no longer be measured. The intertubular surface began etching at nearly the same rate, but then recession slowed for all concentrations and stabilized after recession of less than 1 μm for all but the pH 1 solution. The decrease in recession was attributed to the limitation of contraction of the demineralized collagen scaffold as long as it remained hydrated. Dehydration following etching resulted in significant collapse of the surface, changes in roughness, and a slight decrease in tubule diameter for samples etched for 30 min. Measurements could not be made of the collapse for low pH samples, because shrinkage stresses disrupted the integrity of the reference layer. On rehydration, the dehydrated surfaces underwent an expansion up to the level seen after etching and tubule diameters returned to the etched values. These results indicate that the collapse of demineralized matrix is almost totally recoverable on rehydration. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 500-507, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 71
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 43 (1998), S. 1-14 
    ISSN: 0021-9304
    Schlagwort(e): silicone ; texture ; cell adhesion ; cell cycle ; MTT ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: In vivo biocompatibility of soft-tissue implants is often hampered by development of capsules that eventually might contract and impair implant function. It has been shown that capsule formation can be significantly reduced by using materials with textured surface elements in the micron range. In this study the interaction of human fibroblasts with silicone surfaces was analyzed using cell cycle analysis. Silicone was textured with 2, 5, and 10 μ wide grooves (2MU, 5MU, 10MU, respectively) or kept smooth (SMT). Cell cycle analysis was performed after staining of cells with propidium iodide. Cells proliferated on the fibronectin-preadsorbed silicone, as demonstrated by increased coverage and occurrence of subpopulations in the S and G2/M phase of the cell cycle. Cells on SMT went faster into the S phase than cells on textured silicones. Cells on 10MU showed less proliferation than cells on 2MU and 5MU. Besides the basic percentages of cells in the different cycle phases, DNA profiles were also influenced by incubation time and texture, especially with respect to the presence of hypodiploid populations and asymmetry of the G0/G1 peak. Finally scatter characteristics were influenced. 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay data did not reveal significant differences among the different samples. Fibronectin preadsorption of silicone only resulted in slightly higher MTT conversion. Cell cycle analysis proved to be a sensitive screening method for proliferation on the silicone surfaces and provided information beyond the normal G0/G1, S, and G2/M subpopulations. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 1-14, 1998
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 72
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 517-522 
    ISSN: 0021-9304
    Schlagwort(e): chitin ; chitosan ; canine polymorphonuclear cells ; leukotriene B4 ; prostaglandin E2 ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The effects of chitin and chitosan on the release of arachidonic acid products were investigated in this study. Supernatants of canine polymorphonuclear cell (PMN) suspensions incubated with chitin and chitosan contained a leukotriene B4 (LTB4) concentration high enough to induce canine PMN migration in vitro. The supernatants also contained the same concentration of prostaglandin E2 (PGE2) as that normally found in the peripheral blood of dogs. Intraperitoneal administration of chitosan to dogs induced peritoneal exudative fluid (PEF), but chitin did not. The PEF contained numerous PMNs and macrophages. The supernatant of PEF contained both heat-stable and heat-labile chemotactic factors for canine PMNs. It also contained enough LTB4 to attract the canine PMNs in vitro. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 517-522, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 73
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 508-516 
    ISSN: 0021-9304
    Schlagwort(e): nondestructive analysis ; titanium-ceramic interface ; scanning acoustic microscopy ; protective coating ; four-point bending test ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Failures that occur in titanium-ceramic restorations are of concern in clinical dentistry. The purpose of this study was to nondestructively characterize the internal cracks and nonadherent defects at the titanium-porcelain interface using scanning acoustic microscopy. Titanium samples coated with porcelain without a bonding agent, with sputter coated palladium or chromium as an oxygen diffusion barrier on the titanium, and with the use of a porcelain bonding agent (control group) were compared. The scanning acoustic microscopy analyses were correlated with four-point bending test results. The group that was initially coated with palladium had fewer interfacial defects and a higher load to failure than the control group, and the group that did not contain the bonding agent had a higher void area and a lower load to failure than the control group. The use of chromium produced no differences from the control group. Samples after a four-point bending test were also analyzed by scanning electron microscopy. The scanning electron microscopy was not able to characterize interfacial defects at the fractured titanium-ceramic interface for some of the samples. The validity of nondestructive analysis at the Ti-ceramic interface using scanning acoustic microscopy was demonstrated in this study. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 508-516, 1998.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 74
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 43 (1998), S. 62-68 
    ISSN: 0021-9304
    Schlagwort(e): hip prosthesis ; taper ; standardization ; mechanical properties ; ceramic heads ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Standardization of bores and cones for modular hip prosthesis heads has been addressed by both the International Standard Organisation (ISO) and the American Society for Testing and Materials (ASTM) in response to the need to control the conditions of head-trunnion fit that thereby improves implant safety. Standardization of these conditions could help the surgeon avoid fit mismatch, especially during revision surgery. Instituting a system of standardization without taking all critical parameters into consideration, however, could be more dangerous than no system at all. The current article discusses the main taper parameters that directly influence the performance of ceramic head-metallic trunnion assemblies and argue for standardization that integrates all these parameters. Several examples, based on experimental mechanical tests and finite element analysis, are given to support the argument. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 62-68, 1998
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 75
    ISSN: 0021-9304
    Schlagwort(e): sol-gel films ; titania ; silica ; dip coating ; bioactivity ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Different sol-gel-derived titania and titania-silica films were prepared and their properties related to in vitro bioactivity. The films were prepared by depositing the sols on the substrate surface using a dip-coating method. The sols were monitored carefully as a function of time, using rheological techniques and dynamic light scattering. The topography of the films was characterized using atomic force microscopy, and thicknesses and refractive indexes of the films were evaluated by fitting transmittance spectra measured in a wave length region of 370-1100 nm with a spectrophotometer. The in vitro bioactivity tests were performed in simulated body fluid. Surface topography was found to be of great importance with respect to the bioactivity of the studied films. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 295-302, 1998.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 76
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 272-277 
    ISSN: 0021-9304
    Schlagwort(e): anodic oxide titanium ; hydrothermal treatment ; SA-treated titanium ; biomaterial ; immunocyte ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: All dental root implants come in contact with the oral epithelium, and many complex factors are found to arise in this region. In order to perform a successful dental root implantation, it is necessary to clarify the interaction of the dental root implant material with the host defense mechanisms involved in the specific and nonspecific immune responses to many antigens in oral bacteria and their components. Recently, focusing on developing the dental root implant, the Nikon Corporation improved the surface characteristics of pure titanium even further by developing a hydroxyapatite (HA) layer formed on an anodic titanium oxide film containing Ca and P via hydrothermal treatment (SA treatment). However, since little is known about the effect of SA-treated pure titanium (HA/Ti) on the defense mechanisms of the oral membrane epithelium, we investigated (1) the in vitro proliferation of murine splenic B lymphocytes on the surface of HA/Ti in the presence of three lipopolysaccharide (LPS) concentrations and (2) interleukin-1α (IL-1α) production by the reaction of human peripheral blood mononuclear cells (PBM cells) on the surface of HA/Ti under the same concentrations. After culture, murine splenic lymphocytes were measured by uptake of 3H-thymidine, and cytokine release (IL-1α) from PBM cells was measured by ELISA. Results showed that HA/Ti had hardly any effect on the LPS-induced proliferation of B lymphocytes and IL-1α production. In vitro investigations of the effects of HA/Ti on the LPS-induced proliferation of murine splenic B lymphocytes and IL-1α from PBM cells might be a useful way of elucidating the defense mechanism between implants and the oral epithelium. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 272-277, 1998.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 77
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 614-623 
    ISSN: 0021-9304
    Schlagwort(e): stress analysis ; analysis of bimaterial strips ; thermal incompatibility ; metal-ceramics ; viscoelasticity ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The feasibility of simple tests or analytical methods for prediction of residual stress states in metal-ceramic (MC) prostheses has not been demonstrated. Bimaterial metal-ceramic strips have been proposed to provide sensitive measures of transient and residual stress states through the measurement of midpoint deflection after cooling from the ceramic sintering temperature. The objective of this study was to apply the elastic-viscoelastic analogy to calculate transient and residual midpoint deflections in MC bimaterial strips and to compare these values with deflections measured with a beam-bending viscometer (BBV). Calculations and measurements were made for five MC systems that were found from a clinical study to be “thermally compatible” and from two that were selected as “thermally incompatible” systems. Metal strips, 64 mm in length, 3 mm wide, and either 0.5 mm, 1.0 mm, or 2.0 mm in thickness, were veneered with four 0.25-mm thick layers of opaque porcelain. Midpoint deflection of the MC strips (ceramic oriented in the posterior position) was measured during cooling from an initial temperature of 700°C. In general, the directions of the measured residual deflections did not agree with the “textbook” convention that negative deflections are associated with positive thermal contraction mismatch (αM - αc 〉 0) regardless of metal thickness. For a metal thickness of 0.5 mm, the residual midpoint deflection for all thermal contraction mismatch cases, except one, was positive (upward deflection) whereas the residual midpoint deflections were all negative when the metal thickness was increased to 1 or 2 mm, independent of the thermal contraction mismatch. The best agreement between calculated and measured values of residual midpoint deflection (+16 μm vs. +14 ± 2.3 μm, respectively) was obtained for MC bimaterial strips with a Ni-Cr alloy (0.5 mm thick) while the largest difference (+346 μm vs. +61 ± 43.8 μm) was obtained for MC bimaterial strips with a Au-Pd alloy (0.5 mm thick). In all but one case, changes in deflection direction as a function of metal thickness were correctly predicted by the viscoelastic analysis. The results of this study indicate that a viscoelastic model is useful for estimating thermal compatibility conditions of MC systems. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 614-623, 1998.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 78
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 649-656 
    ISSN: 0021-9304
    Schlagwort(e): flow cytometry ; cell culture ; biocompatibility ; biomaterials ; implants ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Flow cytometry (FCM) was examined as a possible procedure for measuring in vitro the biocompatibility of implant materials for orthopedic and dental surgery. The human osteoblast-like cell line MG63 was grown on hydroxyapatite (HA) and P2O5 glass-reinforced HA composite discs and compared with the same cells grown on polystyrene culture dishes. While morphological observation at the light and electron microscopic levels showed no major deleterious effects, FCM indicated that cell size was somewhat reduced, particularly by growth on the HA composite. Moreover, this material also appeared to delay the progression of the cells from the G0/G1 into the S phase of the cell cycle. In addition to this low level of inhibition of cell growth relative to control cultures, FCM analysis also demonstrated that the glass-reinforced HA caused some down-regulation of the expression of osteocalcin and fibronectin, two antigens which play a vital part in the integrity and function of bone and soft connective tissue, respectively. These results thus show, first, that although HA and the HA composite used in these experiments were generally biocompatible, they nevertheless had certain suboptimal effects on the cells; and second, that FCM could be a highly useful procedure for effectively screening and evaluating important biological responses to implant materials. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 649-656, 1998.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 79
    ISSN: 0021-9304
    Schlagwort(e): bacterial adherence ; contact lens ; nonsteroidal anti-inflammatory drug ; bacterial adherence drug effect ; antimicrobial treatment ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Deposition and aggregation of lachrymal proteins on the contact lens surface can promote bacterial adherence. Lysozyme is the major tear protein and is also mainly responsible for the formation of protein deposits on contact lenses. Nonsteroidal anti-inflammatory drugs (NSAID) prevent protein aggregation. The effect of a water-soluble NSAID drug on bacterial adherence to high-water-content/ionic disposable contact lenses was examined in a radiolabeling study. Dose-related inhibition of adherence of Staphylococcus aureus, S. epidermidis, and Pseudomonas aeruginosa on both pretreated lenses and after adding the drug to the medium was investigated. When the drug was added to the media, maximal inhibition of S. aureus adherence was observed in trypticase soy broth (59-98% at the lower and higher drug concentrations, respectively); inhibition progressively decreased in calf aqueous humor (48-75%), lysozyme (34-63%), and saline (12-20%) solutions. Inhibition of adherence varied with the three bacterial species; it was maximal with S. aureus, intermediate with S. epidermidis, and minimal with P. aeruginosa. When lenses were pretreated with the drug, consistent, and even higher, inhibitory effects were observed. The results suggest that water-soluble NSAIDs could be used in preventive treatments for conjunctivae and corneal infections in contact lens wearers, and may provide a clue as to which compounds might inhibit protein interaction and bacterial adhesion. © 1998 John Wiley & Sons, Inc. J. Biomed Mater Res, 42, 1-5, 1998.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 80
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 38-44 
    ISSN: 0021-9304
    Schlagwort(e): pattern-grafting ; thermoresponsive polymer ; protein adsorption ; cell detachment ; cell culture engineering ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: A thermoresponsive copolymer, poly(N-isopropylacrylamide-co-acrylic acid), was coupled with azidoaniline. The azidophenyl-derivatized copolymer was grafted in a specific pattern on a polystyrene matrix by photolithography. The surface micropattern appeared and disappeared interchangeably, as observed under a phase-contrast microscope, by varying the temperature between 10°C and 37°C. The copolymer-grafted polystyrene surface was hydrophobic at 37°C and hydrophilic at 10°C. Albumin and fibronectin adsorption on the matrix was investigated using the fluorescent-labeling method. Fibronectin adsorbed onto both the grafted and nongrafted regions, while albumin adsorbed more onto the nongrafted regions than the grafted regions. Protein adsorption did not affect surface wettability. Mouse fibroblast STO cells were cultured on tissue culture plates pattern-grafted with the thermoresponsive copolymer. Fibronectin adsorption enhanced cell spreading, while albumin reduced it. When the temperature was lowered, the cells selectively detached from the surface areas grafted with the thermoresponsive copolymer when cultured in serum-free medium; the cells partially detached from these areas when cultured in serum-containing medium. The effect of serum proteins on cell detachment was similar to that caused by a mixture of albumin and fibronectin. Albumin adsorption did not affect the detachment of cells, while fibronectin adsorption inhibited it. The results of the present study indicate that a pattern-grafted, thermoresponsive, azidophenyl-derivatized copolymer can effectively facilitate selective cell detachment under some conditions such as serum-free culture or preadsorption of albumin. The pattern-grafting technique will be useful for qualitative microscopic comparison of surfaces prepared differently on one chip under the same conditions. © 1998 John Wiley & Sons, Inc. J. Biomed Mater Res, 42, 38-44, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 81
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 43 (1998), S. 241-248 
    ISSN: 0021-9304
    Schlagwort(e): ultrahigh molecular weight polyethylene (UHMWPE) ; degradation ; γ sterilization ; mechanical behavior ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The γ radiation sterilization of ultrahigh molecular weight polyethylene (UHMWPE) components in air generates long-lived free radicals that oxidize slowly over time during shelf storage and after implantation. To investigate the combined effects of chemical and mechanical degradation on the mechanical behavior of UHMWPE, sterilized tensile specimens were immersed in 0.5% hydrogen peroxide solution at 37°C for up to 9 months and concurrently subjected to cyclic stress levels of 0 (control), 0 to 5, and 0 to 10 MPa. After chemical and mechanical preconditioning, specimen density was measured using the density gradient column technique. The true stress-strain behavior was measured up to 0.12 true strain and characterized using a multilinear material model, the parameters of which were found to vary linearly with density and cyclic stress history. The mechanical behavior of as-irradiated and degraded UHMWPE was accurately predicted by an analytical composite beam model of the tensile specimens. The results of this study support the hypothesis that chemical and mechanical degradation affect the true stress-strain behavior of UHMWPE. In the future, the material model data presented in this study will enable more accurate prediction of the stresses and strains in UHMWPE components following γ sterilization in air and subsequent in vivo degradation. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 241-248, 1998
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 82
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 43 (1998), S. 277-281 
    ISSN: 0021-9304
    Schlagwort(e): multilaminate sheet ; biaxial testing ; ball burst test ; rehydration effects ; small intestinal submucosa ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The design and test of a multilaminate sheet developed for a hernia repair application is presented. As biomaterial applications become more complex, characterization of uniaxial properties becomes insufficient and biaxial testing becomes necessary. A measure of the in-plane biaxial strength of the device is inferred from a ball burst test. The results of this test for different thicknesses of the device are correlated with the uniaxial strength of the material. A biaxial test such as the ball burst test is more indicative of the properties of a planar material than would be a uniaxial test. The interactions in the biaxial mode of failure are of value and can be related back to a classical uniaxial tensile test from the ball burst test. The material used in this study to fabricate the device was a resorbable biomaterial called small intestinal submucosa (SIS). The effects of rehydration on the stiffness and associated ball burst properties of the SIS device were also measured. It is shown that at a rehydration time of 5 min from a reference dry state, steady-state mechanical properties are reached. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 277-281, 1998
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 83
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 43 (1998), S. 270-276 
    ISSN: 0021-9304
    Schlagwort(e): magnetron sputtering ; calcium phosphates ; subperiosteal ; oesteogenesis ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The aim of this study was to obtain more information about the initial biological events around RF magnetron sputtered calcium phosphate (Ca-P) coatings. Therefore, uncoated and coated disks were inserted subperiosteal into the tibia of a goat. The coatings were deposited on commercially pure titanium. The thickness of the coating was 0.1 or 2.0 μm. All the as-sputtered coatings were subjected to an additional heat treatment for 2 h at 500°C. After 1 and 3 weeks of implantation the experimental disks were retrieved and prepared for histological and physicochemical analysis. The histological results demonstrated that the periosteum covered the specimens after both implantation periods. In between the periosteum and implant an acellular layer and a collagen matrix was observed. Energy dispersive spectrometry revealed that the acellular layer consisted of C, Ca, and P ions for the 0.1 μm thick Ca-P coatings. The 2 μm thick Ca-P coatings also showed the presence of sulfate ions in this layer. Only organic material was found on the titanium disks. Further, SEM showed that even after 3-week implantation, a substantial thickness of both coatings was still maintained. Thin film X-ray diffraction demonstrated that after both implantation periods, the CaP-0.1 coating was still present. FTIR of the retrieved specimens demonstrated on the coated disks the formation of additional carbonate apatite (CO3-AP) associated with an organic phase (NH2 groups). On basis of these findings we conclude that our experimental approach is very suitable for the investigation of the healing process around Ca-P coatings. Further, we again demonstrated that the initial interfacial response to Ca-P materials differs from titanium. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 270-276, 1998
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 84
    ISSN: 0021-9304
    Schlagwort(e): titanium ; dental implant ; osseointegration failure ; surface analysis ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: A multitechnique approach has been used to characterize the surface of nonosseointegrated titanium implants and the surrounding biological tissues. Five pure titanium dental implants were used as reference, and 25 removed implants were studied. Surface and in-depth chemical compositions of the implants (from a total of 16 patients) were investigated by X-ray photoelectron spectroscopy (XPS). Histological slides of the surrounding tissues were examined by light microscopy, XPS, and electron microprobe analysis. None of the failed implants presented the regular surface composition and depth profile of the TiO2 overlayer; foreign elements (Ca, Na, P, Si, Cl, Zn, Pb, and Al) were observed on some implants. Fibrosis, lymphocytic and plasmocytic infiltrates, and granulomatous lesions were detected in the surrounding tissues. XPS and electron microprobe analysis indicated the presence of Zn, Fe, Sn, and Ti in the tissues. As a possible scenario for implant failure, we propose and discuss a oxidoreduction mechanism, leading to a partial dissolution or the complete dissociation of the protective titanium dioxide overlayer and to ion diffusion through the surrounding tissues. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 300-312, 1998
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 85
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 43 (1998), S. 282-290 
    ISSN: 0021-9304
    Schlagwort(e): chitosan ; γ irradiation ; films ; main chain scission ; network structure ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Chitosan has potential biomedical applications that may require the final products to be sterilized before use. The γ irradiation of purified and highly deacetylated chitosan fibers and films at sterilizing doses (up to 25 kGy) caused main chain scissions. The viscosity average molecular weight of the polymer decreased with increasing irradiation dose, the radiation yields of scission being 1.16 in air and 1.53 in anoxia. Preirradiation application of a negative pressure of 100 kPa disrupted the network structure, which may have contributed to the greater radiation yield obtained by chitosan fibers in anoxia. Radiation induced scission of the chitosan chains resulted in a lower glass transition temperature (Tg), indicative of higher segmental mobility. The Tg was below ambient at an irradiation dose of 25 kGy in air. Irradiation in air improved the tensile strength of the chitosan film, probably due to changes in chain interaction and rearrangement. Irradiation in anoxia did not affect film properties significantly, partly because the preirradiation application of negative pressure had a negligible effect on the structure of the chitosan film. Polymer network structure and the irradiation conditions are therefore important determinants of the extent of radiation induced reactions in chitosan. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 282-290, 1998
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 86
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 43 (1998), S. 321-330 
    ISSN: 0021-9304
    Schlagwort(e): ureteral stents ; film depositions ; bacterial biofilms ; XPS ; SEM ; encrustation ; prophylactic antibiotics ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Ureteral stents are commonly implanted to assist the postsurgery flow of urine from the kidney to the bladder. We hypothesized that different surface compositions of stent material could result in different conditioning film depositions and potentially altered receptivity to bacterial biofilms. Using XPS, three types of ureteral stents recovered from 64 patients were found to have adsorbed conditioning films that altered the surface composition of the devices. Elements associated with encrustation (calcium, magnesium and phosphorus) were found on 69% of the silicone latex stents, 44% of the low surface energy (LSe) devices, and 38% of the carbon-rich stents. No statistical difference was found in relation to patient gender, stent type, duration of implantation, and encrustation deposition. The composition of the film suggested that the nature of the underlying material did not significantly alter the elements that adsorbed. Thus, devices may take on a similar surface coat within days, and perhaps hours, of exposure to the host. With respect to dense encrustations, fewer appeared on the LSe devices. SEM confirmed the presence and nature of the film crystals and showed bacterial biofilms adherent to devices and encrustations in three patients who had received prophylactic trimethoprim compared to one on ciprofloxacin. In conclusion, although encrustation deposition and biofilm formation on ureteral stents is not unique to Cook devices, the human model and surface science test systems described here are invaluable to evaluate biomaterials used in patients. Unless biomaterials undergo rigorous analysis in vivo, including true assessment of the outcome of prophylactic antibiotic usage, clinicians will be unable to accurately select the best device and management strategy for a given patient. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 321-330, 1998
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 87
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 387-395 
    ISSN: 0021-9304
    Schlagwort(e): hydroxyapatite ; hydrothermal-electrochemical ; deposition ; titanium ; coating ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Hydroxyapatite crystals were formed on a titanium electrode using the hydrothermal-electrochemical method in an autoclave with two electrodes. The electrolyte dissolving NaCl, K2HPO4, CaCl2 · 2H2O, trishydroxyaminomethane, and hydrochloric acid was maintained at 80°-200°C. After loading of a constant current at 12.5 mA/cm2 for 1 h, the deposited amounts were measured through the weight gain of the electrode. The deposits were characterized by X-ray diffractometry, Fourier transform infrared spectroscopy, field emission-type scanning electron microscopy, field emission-type transmission electron microscopy, and energy dispersive X-ray spectroscopy. The deposited amount increased with electrolyte temperatures up to 150°C and slightly decreased above that temperature. The deposits were identified as hydroxyapatite crystal rods grown along the c axis and perpendicular to the substrate. The crystallinity of the deposited hydroxyapatite increased continuously with the electrolyte temperature and closed to stoichiometric hydroxyapatite. At 150°-160°C, the hydroxyapatite rod grew very homogeneously perpendicular to the substrate, and the edge of the needle had a flat hexagonal plane. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 387-395, 1998.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 88
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 396-402 
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Engineering tissues utilizing biodegradable polymer matrices is a promising approach to the treatment of a number of diseases. However, processing techniques utilized to fabricate these matrices typically involve organic solvents and/or high temperatures. Here we describe a process for fabricating matrices without the use of organic solvents and/or elevated temperatures. Disks comprised of polymer [e.g., poly (D,L-lactic-co-glycolic acid)] and NaCl particles were compression molded at room temperature and subsequently allowed to equilibrate with high pressure CO2 gas (800 psi). Creation of a thermodynamic instability led to the nucleation and growth of gas pores in the polymer particles, resulting in the expansion of the polymer particles. The polymer particles fused to form a continuous matrix with entrapped salt particles. The NaCl particles subsequently were leached to yield macropores within the polymer matrix. The overall porosity and level of pore connectivity were regulated by the ratio of polymer/salt particles and the size of salt particles. Both the compressive modulus (159 ± 130 kPa versus 289 ± 25 kPa) and the tensile modulus (334 ± 52 kPa versus 1100 ± 236 kPa) of the matrices formed with this approach were significantly greater than those formed with a standard solvent casting/particulate leaching process. The utility of these matrices was demonstrated by engineering smooth muscle tissue in vitro with them. This novel process, a combination of high pressure gas foaming and particulate leaching techniques, allows one to fabricate matrices with a well controlled porosity and pore structure. This process avoids the potential negatives associated with the use of high temperatures and/or organic solvents in biomaterials processing. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 396-402, 1998.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 89
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 403-406 
    ISSN: 0021-9304
    Schlagwort(e): calcium phosphate cements ; X-ray diffraction ; setting reactions ; bone apatite ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The setting reactions of calcium phosphate cements in the CaHPO4-α-Ca3(PO4)2 (DCP-α-TCP) system have been investigated. X-ray diffraction (XRD) analyses were performed on DCP-α-TCP cement samples of varying calcium to phosphorus (Ca/P) ratios after setting for 24 h in Ringer's solution at 37°C. XRD measurements showed that the intensity of the DCP peaks decreased linearly as the Ca/P ratio of the mixture increased. However, the intensity of the peaks of a new calcium-deficient hydroxyapatite [CDHA; Ca9(HPO4)(PO4)5OH] precipitating phase increased linearly as the Ca/P ratio increased. Alpha-TCP was not detected after 24 h of setting in any sample. A two-phase mixture XRD model was applied to explain the results, and suitable fits were obtained between observed and expected values of the relevant peak heights. The method used for this study also can be applied to studies of the kinetic behavior of other cement systems. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 403-406, 1998.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 90
    ISSN: 0021-9304
    Schlagwort(e): composite materials ; carbon fiber ; implant ; femoral ; bone ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: A novel composite material with an ultra-high strength and a low elastic modulus called carbon-fiber-reinforced liquid crystalline polymer (LCP/CF) has been developed. We studied the effects of an intramedullary LCP/CF rod on bone in rabbits. A LCP/CF rod of 3.2 mm in diameter and 50 mm in length was introduced into the intramedullary canal of the right femur in ten rabbits weighing an average of 3.6 (3.1-4.2) kg. The follow-up intervals were 3 and 52 weeks. No signs of deformity or osteopenia were seen in the operated femurs in the radiographic, histological, and histomorphometric studies. Histologically, the implant was enclosed by cancellous bone in the metaphyseal area and by a thin cancellous bone cuff in medullary cavity. Bone was able to grow in direct contact with the LCP/CF rod. No signs of degradation of the implants or of adverse tissue reaction were seen. The intramedullary LCP/CF rod had no harmful effects on bone in rabbits. The biocompatibility of the LCP/CF appeared to be good. This novel composite material demonstrates properties that may be useful in orthopedic applications. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 407-411, 1998.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 91
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 412-416 
    ISSN: 0021-9304
    Schlagwort(e): hydroxyapatite ; hydroxyapatite/bone bonding ; hydroxyapatite/bone stability ; homo/heterocoagulation ; hydroxyapatite/bone surface potentials ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Electroacoustic measurements of the zeta (ζ) potential as a function of pH were collected and used to probe the nature of the ionic contributions to the bond formed between synthetic hydroxyapatite (HA) and bone. HA powder and wet bone powder were dispersed into an electrolyte solution comprised of physiologic saline (0.154M NaCl), electroacoustic measurements collected, and the ζ potential calculated as a function of pH. The ζ potential and particle size then were used to calculate the stability of the composite dispersion, where stability is the ability of a particulate suspension to remain unagglomerated. The stability was used to predict the homo- (HA to HA and bone to bone) versus heterocoagulation (HA to bone) behaviors for the HA/bone system. Although single component bone and HA demonstrated stability against agglomeration, the HA/bone interaction was determined to be unstable for all pH levels tested, including pH 7.4, the normal in vivo pH. These results establish one factor responsible for the observed physicochemical bonding between bone and HA noted by many in the orthopedic community. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 412-416, 1998.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 92
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 587-596 
    ISSN: 0021-9304
    Schlagwort(e): gene therapy ; immunoisolation ; human growth hormone ; β-glucuronidase ; factor IX ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Microencapsulation of recombinant “universal” cells with immunoprotective membranes is an alternate approach to somatic gene therapy. Therapeutic gene products secreted by these cells can be delivered to different patients without immunosuppression or genetic modification of the host's cells. The encapsulation of different mammalian cell types (epithelial cells, fibroblasts, and myoblasts) is compared among three alginate-based microcapsules: (1) calcium-linked alginate microcapsules with a solubilized core and a poly-L-lysine-alginate-laminated surface; (2) barium-linked alginate beads with a gelled core; and (3) a hybrid formulation of barium-linked alginate beads with a poly-L-lysine-alginate-laminated surface. The mechanical stability of the different microcapsule types, as measured with a cone-and-plate shearing apparatus, was superior in the two barium-linked alginate beads. All cell types maintained high viability (65-90%) in culture after encapsulation. The recombinant gene products secreted by these cells (human growth hormone MW = 22,000, human factor IX MW = 57,000, and murine β-glucuronidase MW = 300,000) were able to traverse the three microcapsule types at similar rates. Cell numbers within the microcapsules increased twofold to 〉 20-fold over 4 weeks, depending on the cell type. Epithelial and myoblast cell numbers were not affected by microcapsule formulation; however, fibroblasts proliferated the most in the calcium-linked alginate spheres. These results show that for culturing fibroblasts in a mechanically stable environment the classical calcium-linked microcapsules are adequate. However, where mechanical stability is a more critical requirement, the solid barium-linked gelled beads are more appropriate choices. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 587-596, 1998.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 93
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 626-633 
    ISSN: 0021-9304
    Schlagwort(e): magnesium ; calcifying matrix ; osteoblast-like cell culture ; apatite ; collagen sponge ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The induction of a calcifying matrix is of great interest in the restoration of bone defects. In a previous in vitro study we demonstrated that a collagen sponge constituted of type I collagen fibrils, chondroitin sulfates, and hydroxyapatite crystals induces an earlier and a more abundant synthesis of a new extracellular calcifying matrix than do other biomaterials such as collagen or hydroxyapatite alone. Bone mineral contains various amounts of magnesium ions, either adsorbed at the surface of apatite crystals or incorporated inside the crystal structure. Magnesium is known to reduce the degradation rate of tricalcium phosphate ceramics and to influence the crystallization of mineral substance. Thus we evaluated two sponges modified with different substituted apatites. The substituted low magnesium-containing apatite sample decreased the osteoinductive properties of the sponge whereas the substituted high magnesium-containing apatite sample had a toxic effect on bone cells and prevented the formation of any extracellular matrix. Such a toxic effect can be explained by the presence of large numbers of magnesium ions released into the culture medium even though at physiological level magnesium is able to promote bone mineralization and to control the growth of hydroxyapatite crystals. Thus collagen sponges containing hydroxyapatite remain one of the most appropriately evaluated biomaterials used for the restoration of periodontal pockets and bone defects. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 626-633, 1998.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 94
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 261-265 
    ISSN: 0021-9304
    Schlagwort(e): UHMWPE ; compressive creep ; wear ; linear penetration ; total joint prosthesis ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The static compressive creep behavior of ultrahigh-molecular-weight polyethylene (UHMWPE) was studied under physiologic conditions. Specimens were machined from the center and periphery of extruded GUR 4150HP rod stock and were subjected to constant pressures of 2, 4, or 8 MPa for intervals as long as 104 min. The creep strain (creep ÷ initial thickness) was compared to the pressure and duration of loading by using analysis of variance and linear regression analysis. The amount of creep strain increased rapidly in the early period of testing and was followed by a reduced rate of creep, which reached a steady state after approximately 4000 min. The amount and rate of creep strain increased linearly with pressure. Surprisingly, the rate of creep strain varied with the radial position in the rod stock: specimens obtained from the periphery had 8-19% larger creep strain rates than did specimens obtained from the center (p = 0.1 to p 〈 0.001). These results advance the characterization of creep's contribution to the in vivo penetration of the metallic component into the UHMWPE component, thereby facilitating the measurement of true in vivo wear. These data also help explain the azimuthally nonuniform deformation observed in retrieved acetabular cups. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 261-265, 1998.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 95
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 286-291 
    ISSN: 0021-9304
    Schlagwort(e): cytotoxicity ; biomaterials ; standards ; microplate ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: We investigated the cytotoxicity of different dental materials according to the study protocol adopted by our lab for the screening of new materials. Experimental parameters used in such testing are addressed mainly in documents EN 30993 “Biological evaluation of medical devices, Part 5: Tests for cytotoxicity: in vitro methods” and “Biological evaluation of medical devices, Part 12: Sample preparation and reference materials.” Cells were cultured in microplates and challenged with aqueous extracts of the materials. The assay methods were neutral red- and propidium iodide-uptake assays, both indicative of cell viability and able to provide quantitative data. The observation of contrasting results for one material using the above-mentioned methods raised some concern about the assay system used. With further experimentation, it appeared that a sustained release of volatile substances still present in one extract exerted a toxic effect in neighboring cultures. It is concluded that in the microenvironment of a microplate the distribution of samples cannot be disregarded, as it may be responsible for toxicity cross-contamination. Moreover, the use of more than one single method has to be recommended in cytotoxicity testing, in order to avoid false positive results due to experimental artifacts. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 286-291, 1998.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 96
    ISSN: 0021-9304
    Schlagwort(e): fungi ; chitin ; chitosan ; polysaccharides ; Rhizomucor miehei ; Rhizopus oryzae ; Agaricus bisporus ; Fusarium graminearum ; Phycomyces blakesleeanus ; fibroblast proliferation ; hydrogen peroxide ; wound healing ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Agaricus bisporus, Fusarium graminearum, Phycomyces blakesleeanus, unbleached and bleached, Rhizomucor miehei, and Rhizopus oryzae were examined as sources of fungal chitin/chitosan. The nitrogen content of the alkali-treated mycelia/sporangiophores obtained after optimization of culture conditions, and of similarly treated A. bisporus stipes, was 2.87, 1.29, 6.27, 6.50, 4.80, and 4.95% w/w, respectively, which relates to an estimated chitin content of 42, 19, 91, 94, 70, and 72%, respectively. The hydrogen peroxide (H2O2)-generating ability of the treated fungal materials after 8 h at pH 7.4 and 37°C decreased in the order R. oryzae 〉 P. blakesleeanus unbleached ≈ R. miehi 〉 F. graminearum 〉 A. bisporus 〉 P. blakesleeanus bleached. This did not correlate with estimated chitin content. The effect of these fungal materials on the rate of proliferation of murine L929 fibroblasts in culture also was examined. Both pro- and antiproliferant effects were observed. Significant (P 〈 .05) proproliferant effects were observed on day 6 with R. miehei, R. oryzae, and P. blakesleeanus (unbleached and bleached) at 0.01% w/v. The greatest antiproliferant effect was observed with R. oryzae at 0.05% w/v on day 6 (-63% relative to the control, P 〈 .05; cell viability, 95%). In contrast, A. bisporus failed to affect cell yield significantly at either 0.01 or 0.05% w/v. Addition of catalase to cultures containing R. oryzae or R. miehei at 0.05% w/v failed to abolish the antiproliferant effect on day 3, instead producing a small but significant (P 〈 .05) increase in the effect. Catalase also failed to affect significantly the antiproliferant effect of F. graminearum at 0.05% w/v, but did abolish the proproliferant effect of P. blakesleeanus (unbleached and bleached) on day 3. Overall, our results suggest that the H2O2 being generated by the fungal materials modulates cell proliferation but that this effect is superimposed upon a H2O2-independent antiproliferant effect manifesting itself at the higher concentrations of fungal material. The antiproliferant effect was not attributable to Ca2+, Mg2+, or Fe2+ depletion although chelation of Fe2+ did correlate with H2O2-generating ability. Only P. blakesleeanus appears to lack this antiproliferant activity while retaining H2O2-generating activity. These results may aid the selection of fungal chitin/chitosan for further evaluation as a potential wound management material. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 300-307, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 97
    ISSN: 0021-9304
    Schlagwort(e): calcium alginate dressing ; wound healing ; foreign body ; occlusive dressing ; artificial skin ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Calcium alginate dressings have beneficial effects on wound healing by providing a moist wound environment. However, cytotoxicity and the nonbiodegradable nature of calcium alginate dressings induce unresolved chronic foreign-body reaction. In this study, a novel freeze-dried alginate gel dressing (AGA-100) low in calcium ions was evaluated for cytotoxicity to L929 cells in vitro and in full-thickness pig wounds in vivo. Cytotoxicity testing on L929 cells showed the cytocompatibility of AGA-100 extracts, while extracts from Kaltostat, a well-established alginate dressing, induced cytopathic effects. In an in vivo study using pigskin, AGA-100, Kaltostat, and gauze were applied on 1-in-diameter circular full-thickness wounds on the back of pigs and the time course of wound closure was evaluated. Kaltostat and gauze dressings were used as controls. For histologic evaluation, wound tissue was harvested on day 18. AGA-100-treated wounds showed rapid wound closure compared to control wounds on day 15. Foreign-body reaction was marked in Kaltostat- and gauze-treated wounds, and differed significantly from AGA-100-treated wounds. Based on these data, AGA-100 could reduce the cytotoxicity to fibroblasts and foreign-body reaction that have been observed with currently available calcium alginate dressings; it was also found to be useful as an alginate dressing. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 317-322, 1998.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 98
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 341-350 
    ISSN: 0021-9304
    Schlagwort(e): bacterial adhesion ; Staphylococcus epidermidis ; polysaccharide adhesin (PS/A) ; slime ; surface hydrophobicity ; biomaterials-adverse effects ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Staphylococcus epidermidis capsular polysaccharide adhesin (PS/A) and slime were studied as possible mediators of bacterial adhesion to NHLBI polyethylene (PE) under dynamic flow. This putative interaction was examined by quantifying the adhesion of M187 (PS/A+, slime+) parent strain and isogenic transposon mutant strain sn3 (PS/A-, slime-) to polyethylene (PE) under a range of physiologic shear stress conditions in both phosphate-buffered saline (PBS) and 1% platelet poor plasma (PPP). No significant differences in adhesion were noted between the M187 and sn3 strains in either test medium. However, adhesion of both strains in 1% PPP was decreased 75-95% compared to adhesion in PBS. In PBS, adhesion was shear stress dependent from 0-15 dyne/cm2, after which adhesion was comparatively shear stress independent. Adhesion in 1% PPP was independent of shear stress. Epifluorescent imaging of both strains labeled for slime confirmed the presence of slime on the surface of M187 and suggested that PS/A and slime promote the formation of large aggregates, as aggregates were totally absent in the images of the sn3 strain. The results suggest that PS/A and slime do not mediate S. epidermidis adhesion to bare PE or PE with adsorbed plasma proteins, but may be necessary for intercellular adhesion, which is important for biofilm formation. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 341-350, 1998.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 99
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 373-379 
    ISSN: 0021-9304
    Schlagwort(e): cortical bone ; laser speckle ; strain rate ; nondestructive evaluation ; biomaterials ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: We investigated the micromechanical behavior of porcine femoral cortical bone using a novel, nondestructive, noncontacting, laser-based strain measurement technique. The technique is based upon the well-known concept of tracking translating laser speckle with a linear array CCD camera, but employs a unique data-processing scheme based upon a two-dimensional frequency transform of the data. The method proved to be successful in evaluating strain rates in the bone samples. Measured strain rates ranged between 4.61 and 23.84 με/s. Total strains recorded were between 3.7 and 19.1 με. Estimated Young's moduli averaged 9.01 ± 3.93 GPa, which, considering the extremely slow strain rates, is an acceptable value for porcine cortical bone. General advantages of the technique include high sensitivity, insensitivity to zero-mean noise sources, compact design, and the fact that it is truly noncontact. A brief discussion of possible error sources within the method is also given. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 373-379, 1998.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 100
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 407-414 
    ISSN: 0021-9304
    Schlagwort(e): plasma spraying ; amorphous phases ; hydroxyapatite ; coating microstructure ; X-ray diffraction ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The amorphous phase content of air plasma-sprayed hydroxyapatite coatings is dependent upon spraying and deposition conditions. X-ray diffraction and optical microscopy were used to investigate the influence of spray parameters on the formation of the amorphous phase. Results show three factors which most influence the formation of the amorphous phase: dehydroxylation of the molten particle during flight, the cooling rate as it impinges onto the metal substrate, and the substrate temperature. Crystalline regions were identified as unmelted particles and elongated recrystallized areas. Amorphous phase regions vary throughout the coating but are more commonly found at the coating-substrate interface, i.e., the regions decrease toward the surface of the coating. Such an inhomogeneous distribution of phase content is expected to affect the clinical process of bone deposition, and therefore successful implant fixation. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 407-414, 1998.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...