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  • Articles  (34)
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  • Polymer and Materials Science  (34)
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  • 1995-1999  (34)
  • 1980-1984
  • 1996  (34)
  • Medicine  (34)
  • 1
    Electronic Resource
    Electronic Resource
    Surface roughness modulates the local production of growth factors and cytokines by osteoblast-like MG-63 cells (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 32 (1996), S. 55-63 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Titanium (Ti) surface roughness affects proliferation, differentiation, and matrix production of MG-63 osteoblast-like cells. Cytokines and growth factors produced in the milieu surrounding an implant may also be influenced by its surface, thereby modulating the healing process. This study examined the effect of surface roughness on the production of two factors known to have potent effects on bone, prostaglandin E2 (PGE2) and transforming growth factor β1 (TGF-β1). MG-63 cells were cultured on Ti disks of varying roughness. The surfaces were ranked from smoothest to roughest: electropolished (EP), pretreated with hydrofluoric acid-nitric acid (PT), fine sand-blasted, etched with HCl and H2SO4, and washed (EA), coarse sand-blasted, etched with HCl and H2SO4, and washed (CA), and Ti plasma-sprayed (TPS). Cells were cultured in 24-well polystyrene (plastic) dishes as controls and to determine when confluence was achieved. Media were collected and cell number determined 24 h postconfluence. PGE2 and TGF-β1 levels in the conditioned media were determined using commercial radioimmunoassay and enzyme-linked immunosorbent assay kits, respectively. There was an inverse relationship between cell number and Ti surface roughness. Total PGE2 content in the media of cultures grown on the three roughest surfaces (FA, CA, and TPS) was significantly increased 1.5-4.0 times over that found in media of cultures grown on plastic or smooth surfaces. When PGE2 production was expressed per cell number, CA and TPS cultures exhibited six- to eightfold increases compared to cultures on plastic and smooth surfaces. There was a direct relationship between TGF-β1 production and surface roughness, both in terms of total TGF-β1 per culture and when normalized for cell number. TGF-β1 production on rough surfaces (CA and TPS) was three to five times higher than on plastic. These studies indicate that substrate surface roughness affects cytokine and growth factor production by MG-63 cells, suggesting that surface roughness may modulate the activity of cells interacting with an implant, and thereby affect tissue healing and implant success. © 1996 John Wiley & Sons, Inc.
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of titanium surface roughness on chondrocyte proliferation, matrix production, and differentiation depends on the state of cell maturation (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 30 (1996), S. 145-155 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Although it is well accepted that implant success is dependent on various surface properties, little is known about the effect of surface roughness on cell metabolism or differentiation, or whether the effects vary with the maturational state of the cells interacting with the implant. In the current study, we examined the effect of titanium (Ti) surface roughness on chondrocyte proliferation, differentiation, and matrix synthesis using cells derived from known stages of endochondral development. Chondrocytes derived from the resting zone (RCs) and growth zone (GCs) of rat costochondral cartilage were cultured on Ti disks that were prepared as follows: HF-HNO3-treated and washed (PT); PT-treated and electropolished (EP); fine sand-blasted, HCl-H2SO4-etched, and washed (FA); coarse sand-blasted, HCl-H2SO4-etched, and washed (CA); or Ti plasma-sprayed (TPS). Based on surface analysis, the Ti surfaces were ranked from smoothest to roughest: EP, PT, FA, CA, and TPS. Cell proliferation was assessed by cell number and [3H]-thymidine incorporation, and RNA synthesis was assessed by [3H]-uridine incorporation. Differentiation was determined by alkaline phosphatase specific activity (AL-Pase). Matrix production was measured by [3H]-proline incorporation into collagenase-digestible (CDP) and noncollagenase-digestible (NCP) protein and by [35S]-sulfate incorporation into proteoglycan. GCs required two trypsinizations for complete removal from the culture disks; the number of cells released by the first trypsinization was generally decreased with increasing surface roughness while that released by the second trypsinization was increased. In RC cultures, cell number was similarly decreased on the rougher surfaces; only minimal numbers of RCs were released by a second trypsinization. [3H]-thymidine incorporation by RCs decreased with increasing surface roughness while that by GCs was increased. [3H]-Uridine incorporation by both GCs and RCs was greater on rough surfaces. Conversely, ALPase in the cell layer and isolated cells of both cell types was significantly decreased. GC CDP and NCP production was significantly decreased on rough surfaces while CDP production by RC cells was significantly decreased on smooth surfaces. [35S]-sulfate incorporation by RCs and GCs was decreased on all surfaces compared to tissue culture plastic. The results of this study indicate that surface roughness affects chondrocyte proliferation, differentiation, and matrix synthesis, and that this regulation is cell maturation dependent. © 1996 John Wiley & Sons, Inc.
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  • 3
    Electronic Resource
    Electronic Resource
    Novel fracture toughness test using a notchless triangular prism (NTP) specimen (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 31 (1996), S. 457-463 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The aim of this study was to develop and validate a new method for determining the fracture toughness of materials and adhesive interfaces. The new test specimen is a notchless triangular prism (NTP) which, when placed in the testing holder, achieves a configuration similar to that of the standard chevron-notched short rod (CNSR) specimen. It can be cast, ground, or simply machined easily and reproducibly without cutting an initial notch. Finite element analysis of a modeled NTP specimen loaded in tension showed a stress distribution similar to a CNSR specimen. A very good correlation was obtained between the NTP and CNSR fracture toughness values of poly(methyl methacrylate) during a calibration study. Fracture toughness values similar to those reported in the literature were obtained for several dental materials and one adhesive interface using the NTP test. The fracture patterns were indicative of plane strain conditions during testing. All bulk specimens and most of the adhesive specimens showed crack arrest, which suggested a stable, well-controlled testing procedure. These results suggest that the NTP fracture toughness test can be used to determine the fracture mechanics of bulk materials and adhesive interfaces. © 1996 John Wiley & Sons, Inc.
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  • 4
    Electronic Resource
    Electronic Resource
    Crystallization of experimental bioactive glass compositions (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 32 (1996), S. 119-124 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Crystallization kinetics studies for six experimental glass formulations in the system Na2O-CaO-SiO2-P2O5 synthesized by wet chemistry were conducted by means of differential thermal analysis. These glasses had CaO/P2O5 and SiO2/(CaO + Na2O) ratios ranging from 8.74-3.38 and 0.92-3.03, respectively. Samples of each glass (n = 30 were heated from 23 to 1250°C under N2 atmosphere at heating rates ranging from 10 to 50°C/min. Glass-ceramics were obtained after heat treating the initial glasses at temperatures determined from their DTA exotherms. The activation energy of crystallization for each glass composition was calculated from an expression-relating log-heating rate and the reciprocal of the exothermic peak temperature. The compositions of the six glasses were significantly different (p = 0.05). The activation energy of crystallization (Q) values ranged from 196 to 782 kJ/mole. A correlation was obtained between Q and CaO/P2O5 and between Q and the Young's modulus (p 〈 0.001). Two of the six glasses exhibited bulk crystallization. X-ray diffraction studies showed that four of the six glasses exhibited different proportions of crystalline phases following heat treatment. These phases were wollastonite (CaSiO3), Na2CaSi3O9, combeite [Na4Ca3SI6O16(OH)2], and some unidentifiable phases. Two of the six bioceramic materials had a mixture of unknown crystalline phases. © 1996 John Wiley & Sons, Inc.
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  • 5
    Electronic Resource
    Electronic Resource
    Collagen synthesis by vascular smooth muscle cells in the presence of antiproliferative polysaccharides (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 30 (1996), S. 501-508 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Production of various components of the extracellular matrix (ECM) modulates biological functions of the vascular tissue. This process is generally amplified in pathologic states as atherosclerosis. Atheroma originates from smooth muscle cells (SMC) which have migrated and proliferated in the vascular intima. In this study we investigated protein synthesis, collagen synthesis, and types I, III, and V collagen distribution by SMC in the presence of three families of water-soluble polysaccharides, heparin, fucans, and derivatized dextrans. We observed that fucan and derivatized dextran were able, as was heparin, to inhibit rat aortic SMC growth in culture. We then analyzed collagen modulation by measuring the incorporation of the radiolabeled precursor (3H)-proline into vascular SMC. Our results showed uncoupling of the antiproliferative capacity with collagen biosynthesis. However, fucan, the most antiproliferative polysaccharide, was also the most active in inhibiting protein and collagen synthesis. In addition, compounds that decreased total collagen synthesis preferentially increased the proportion of cell-associated collagen. Interestingly, only the antiproliferative polysaccharides inhibited significantly type V collagen biosynthesis. These new biomaterials appear to be valuable tools to study and control extracellular-matrix interactions with cells from the vascular walls. © 1996 John Wiley & Sons, Inc.
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  • 6
    Electronic Resource
    Electronic Resource
    Shape and size of virgin ultrahigh molecular weight GUR 4150 HP polyethylene powder (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 33 (1996), S. 65-71 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Sizes and shapes of micron- and submicron-sized structures in four lots of virgin GUR 4150 HP ultrahigh molecular weight polyethylene powder were determined by using low-voltage scanning electron microscopy and image analysis. One thousand two hundred micron-sized virgin powder particles and 1200 of their constituent submicron-sized structures were analyzed. The mean maximum diameter of the micron-sized particles was 81.3 μm, and that of the submicron-sized particles was 0.82 μm. Particle shapes, as determined by the aspect ratio (maximum diameter ÷ minimum diameter), were remarkably consistent from lot to lot and between the micron- and submicron-sized particles (1.55 versus 1.53, respectively). Significant lot to lot variability was observed in the sizes of the micron-sized particles, and the size distribution of the submicron-sized particles closely follows the size distribution of the submicron-sized particles observed in tissue retrievals. This variability leads to questions about variability in polyethylene quality and in vivo wear performance. Size similarity between the submicron-sized particles retrieved from tissues and that observed in virgin powder supports the hypothesis that polyethylene debris has two origins: particles released from structures retained from the virgin powder, and particles generated de novo by friction and wear. © 1996 John Wiley & Sons, Inc.
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  • 7
    Electronic Resource
    Electronic Resource
    Testing mode and surface treatment effects on dentin bonding (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 32 (1996), S. 533-541 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The goal of this project was to evaluate the effect of the following variables on shear dentin-bonding test results: mode of testing (cyclic fatigue versus static loading), surface treatments (32% phosphoric acid, 10% phosphoric acid, and no treatment [unetched]), and type of shear test (traditional planar versus push-out). All teeth were stored in distilled water and tested in a shear mode at a loading rate of 2 mm/min. The specimens were loaded in static or cycled for 1000 cycles using a staircase approach or until fracture, whichever occurred first. On samples with etched dentin surfaces, the push-out test did not demonstrate a significant difference in measured bond strength when compared with results from the planar test, although sample preparation was more labor-intensive. The bond strength resulting from cyclic fatigue of the etched specimens was approximately 51% of the static loading value. Ten percent phosphoric acid was as effective as 32% phosphoric acid for dentin bonding. Finite-element analysis indicated that the traditional planar shear test produces flexure of the specimen and high tensile stress magnitudes within the resin bonding layer. The push-out test produces elevated compressive stresses localized in the composite along the circumference of the punch. Shear stresses in the resin bonding layer are similar for both testing methods at the same loading element contact force. © 1996 John Wiley & Sons, Inc.
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  • 8
    Electronic Resource
    Electronic Resource
    Technical note: Activation of the plasma coagulation system induced by some biomaterials (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 31 (1996), S. 145-148 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The ability of some biomaterials to activate plasma coagulation system was examined in vitro. After contact of platelet-rich plasma with biomaterials, some markers of the thrombin formation process, i.e., fragment 1 + 2 and fibrinopeptide A, and some inhibitors of the blood coagulation mechanism were tested. Fragment 1 + 2 and fibrinopeptide A were found to be increased by all of the materials, though to a different extent. In particular, fragment 1 + 2 and fibrinopeptide A were significantly increased upon contact with polybutylene terephthalate and with collagen coated polyethylene terephthalate, respectively. Also, antithrombin III was shown to decrease following exposure to biomaterials, but statistical significance was found only for polyethylene terephthalate and polyvinylacetate. As a result of this wide range of variability in the parameters, it is advisable to explore the plasma coagulation system with a multiparametric approach in which thrombin formation and coagulation inhibitors are thoroughly investigated. © 1996 John Wiley & Sons, Inc.
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of biomaterial surface charge on the inflammatory reponse: Evaluation of cellular infiltration and TNFα production (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 31 (1996), S. 139-144 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A rat model was used to investigate the effect of net surface charge on polymer biocompatibility and its potential to modify and stimulate the inflammatory response. Poly(ether)urethane was taken as the base material and the net charge altered by introducing sulphonate ionic groups to the polymer backbone. Three differently charged poly(ether)urethanes were made with 10, 20, and 30% sulphonate substitution, giving a range of negative charge, with unmodified poly(ether)urethane used as a control. The polymers were implanted intramuscularly into rats for 2 days, and for 1, 2, and 12 weeks. After explantation, the cellular infiltration in the tissue surrounding the implants was evaluated using immunohistochemistry to stain for specific cell types: macrophages, neutrophils, lymphocytes, and the cytokine TNFα. In situ hybridization was used to detect expression of mRNA encoding TNFα. Stained sections were analyzed and the cellular response quantified using image analysis. Initially macrophages and neutrophils were observed around all the materials, but neutrophils were absent in all samples at 12 weeks. The 2-day time point had significantly more macrophages than the later time points. By 2 weeks the 20%-charged polymer elicited significantly less neutrophil infiltration than the other three polymers. In all samples where macrophages were observed, cells staining positive for TNFα protein and message also were observed. No T or B lymphocytes were observed in the infiltrates around the materials at any time point. The results indicate that surface charge can influence the early phase acute inflammatory response to an implanted material. © 1996 John Wiley and Sons, Inc.
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  • 10
    Electronic Resource
    Electronic Resource
    Measurement of bacterial growth rates on polymers (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 32 (1996), S. 271-278 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A video microscope system and a mathematical model were developed to observe and model the early stage of bacterial growth on polymer surfaces. Glass slides were coated with polyorthoester, poly(L-lactic acid), and polysulfone, and inserted into a laminar flow cell to expose them to bacterial cultures of Staphylococcus epidermidis, Pseudomonas aeruginosa, or Escherichia coli. The free energy of adhesion (ΔFadh) was determined from contact-angle measurements. The microscopic observations along with the mathematical model allowed measurement of the rates of adhesion, release, and growth. The growth rate of P. aeruginosa on the various surfaces correlated to the ΔFadh. The growth rates of all species on all of the surfaces were slower than the growth rates of the bacteria in suspension. The mathematical model is valid for early growth before the bacteria form a complete monolayer, and is useful in predicting and modeling early growth of bacteria on implanted biomaterials. © 1996 John Wiley & Sons, Inc.
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