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  • 1
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    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 2 (1991) 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 2
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 2 (1991), S. 215-215 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 3
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 2 (1991), S. 217-217 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 4
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 2 (1991), S. 261-267 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A transparent poly(vinyl alcohol) hydrogel disc covalently immobilized with Type I collagen, fibronectin, and an adhesive oligopeptide and preseeded with corneal epithelial cells was implanted in rabbit cornea using a technique of lamellar keratoplasty, and the tissue response was studied by light and electron microscopy. Covalent immobilization of type I colagen on the surfaceof hydrogel was found to support growth and adhesion of the corneal epithelium in vitro. the in vivo experiment showed that cell seeding could prevant infection of the hydrogel. However, the implanted disc was rejected from the host cornea by epithelial downgrowth and the exchange between the seeded cells and host corneal epithelia was not observed until 14 days after surgery. The rejection might have occurred because of unsatisfactory fixation of the hydrogel to the host cornea.
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  • 5
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 2 (1991), S. 277-280 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 6
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 2 (1991), S. 273-276 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Fibroblasts in culture and in vitro have been shown to interact with certain surface morphological phenomena. It was the aim of the present study to determine cellular morphological interactions with surface grooves of subcellular dimensions. The silicon oxide layer of a wafer was photoetched, which resulted in a regular micromorphology with linear rectangular shaped microbars and microgrooves 1, 1.5, and 2 μm in diameter and distance from each other. Human fibroblasts were seeded on the sterile specimen and incubated for 48 h. Fluorescence microscopy of the plates revealed that all the cells were aligned parallel to the etched grooves on the test specimen, whereas on the controls the cells were randomly orientated. It could be demonstrated by scanning electron microscopy that single cels were flattened over the surface and conformed to the silicon microgrooves. This indicates that fibroblasts are orienting during adhesion and conform to the surface microtexture to gain a maximum contact area on the presented surface.
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  • 7
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 2 (1991), S. 281-283 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The patent literature can be a morass of confusion. It is complicated by legalese, often uncommunicative titles, and difficult, as well as cryptic, categorization. To kiip current with the broad arena of patents on biomaterials and medical devices is much more difficult than keeping current with the scientific literature of the international journals.It is the goal of my column to provide readers with techniques and tools to better utilize this rich source of scientific information. Also, I intend to provide focused surveys of recent patents in specific areas relating to biomaterials and medical devices. Finally, I will try to include discussion of what constitures patentable material and educate those of us who are new to patent literature and new to the requirements of applying for patents for our discoveries.I appeal to the readership to submit requests for specific areas to be addressed in this column. The interaction will enrich us all.
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  • 8
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 2 (1991), S. 209-210 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of my column is to provide readers with current information on biomaterials related standards produced by both private groups and government agencies, and also on standards-related activities. Standards are descriptive documents given official status by their producers, and in the case of biomaterials, they are generally intended to provide formalized descriptions, of (a) materials used in the construction of medical devices, (b) materials used directly in surgical repairs, (c) test methods to evaluate materials for such applications, and (d) methods for handling or processing such materials.Please consider this column not only a place to obtain biomaterials standards information, but also a place to submit news of biomaterials standards developments in order to get the information before the public. This invitation extends to members of all professional organizations and government agencies in the United States and abroad who are active in standards development and would like specific activities or standards publicized. I will present the information in this column to the extent that allotted space allows.At last, a caveat-since this is a column, it contains both factual information and opinions. I will make every effort to make it clear which is which. Also, as a frame of reference, please note that this column was written and submitted in June 1991.
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  • 9
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The present study was conducted to compare the push-out strength of the treated and control samples obtained after implantation of intramedullary rod in canine femurs with bone cement to simulate the femoral stem implantation for 2 weeks, 3 and 6 months. Contralateral femur served as control. The result showed a significant decrease in push-out interfacial strength after shock wave treatment (average 48.4% decrease compared with control, p 〈 0.0001) which is similar to the in vitro results. There was no significant difference if the shock treatment was applied and left for 2 weeks or 4 weeks compared to the ones tested immediately after sacrifice. There were some soft tissue damage immediately following shock treatment in the focal area but this returned to normal in 2 weeks. Human cadaveric femoral bones and the canine bone (the dosage level was higher for the human bone than canine). The number of impacts used to extract the bone cement plug out of a human femur segment (5-cm long) decreased about 68% at 23 and 25 kV treatment power level. These preliminary studies indicate that the shock wave can be utilized to reduce the interfacial strength of the bone and bone cement although more studies are needed to assess its efficacy in terms of cost, long-term effect on patients and the exact mechanism of the loosening before this technique can be used clinically.
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  • 10
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 2 (1991), S. 211-212 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 11
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    Journal of Applied Biomaterials 2 (1991), S. 213-213 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 12
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 2 (1991), S. 219-229 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We have developed a bioactive bone cement using CaO—SiO—2—P2O5—CaF2 glass powders and ammonium phosphate solution, and investigaed ist histological and mechanical characteristics in vivo. A bone defect was drilled in the proximal metaphysis of the rat tibia and filled with the bioactive bone cement in paste form or polymethylmethacrylate (PMMA) bone cement in the dough state. The cements were allowed to harden in situ. Histological examinationdemonstrated direct bonding between the new cement and bone by 4 weeks. The bioactive bone cement did not degrade up to 24 weeks postimplantation. The inflammatory reaction to the bioactive bone cement was less intense than the reaction induced by PMMA. Changes in the mechanical properties of the cement in vivo were studied by implanting hardened cylindrical specimens of both types of cement into the hindlimb muscles of ras of rats for 12 weeks. The compressive strength of the bioactive cement increased significantly after implantation, and reached 68 MPa in 1 week and 73 MPa in 4 weeks. These values were comparable to those of PMMA, and were maintained up to 12 weeks after implantation. This bioacive bone cement hadens in situ within a few minutes with negligible rise of temperature and can be easily handled as a paste for filling bone cavities of different shapes. In addition, this cement has good osteoconductive and bone bonding potential and fairly high mechanical strength. Therefore, this new cement could be used both as a bioactive bone cement and bone defect filler.
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  • 13
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    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 2 (1991), S. 13-22 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A test methodology was developed for exposing degradable polymer test specimens to a simulated chemical and mechanical body environment and then testing them periodically to detect changes in stress-strain behavior. Poly(ortho ester) specimens were exposed to cyclic loading in aerated tris-buffered saline (pH = 7.4) at 37°C. Specimens were removed at various time periods and the mechanical properties determined. To determine the effects of cyclic loading alone, additional specimens were cycled in air for the same cyclic periods and tested in the same manner. To determine the effects of a constant load on degradation rate, other specimens were subjected to a static load while exposed to trisbuffered saline. Additional specimens were subjected to immersion in tris-buffered saline without loading.Exposure to tris-buffered saline alone had a small effect on the rate of change of the mechanical properties of the poly(ortho ester) specimens while cyclic loading in air alone had no effect. However a combination of both exposure to tris-buffered saline and a static load decreased the flexural yield strength by 29% and the modulus of elasticity by 20% after 40 days, and a combination of both exposure to tris-buffered saline and cyclic loading decreased both the flexural strength and modulus by 75% after 40 days.
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  • 14
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    Journal of Applied Biomaterials 2 (1991), S. 23-28 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: As-polymerized poly(L-lactide) test rods were sterilized by seven different specially designed computer-operated autoclaving programs. As a control, common hospital sterilization was performed. In all cases, the molecular weight decreased after sterilization. A short time high-temperature sterilization lead to less molecular weight decrease than a low sterilization temperature cycle with a longer sterilization time. Regular hospital sterilization significantly reduced the elongation at break and also resulted in a decrease of 35% in tensile strength. The program causing minimal damage to the material properties was studied in detail. This program, with a steriliztioan period of 60 s and 129°C, was effective for PLLA steriliztation and also looks very promising for sterilization of other thermo- and moisture-labile polymers.
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  • 15
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    Journal of Applied Biomaterials 2 (1991), S. 37-40 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Previous studies have shown that synthetic calcium phosphate ceramics are biocompatible materials capable of providing scaffolding for new bone growth as well as osteogenesis. In particular, hydroxylapatite (HA) is less soluble than β-tricalcium phosphate (β-TCP) which has a higher degree of bioactivity. An implant made of dense hydroxylapatite shows substantially less bone growth than an implant made of a suitable HA/TCP ratio.1 Therefore, since biological response to the two materials is different, it is essential to have some means of determining the ratio of hydroxylapatite to β-tricalcium phosphate to ensure quality control of the synthetic ceramic as well as optimum biological response. In this study, a calibration curve was developed for x-ray diffractometer examination of mixtures of HA and β-TCP. The accuracy of using the diffractometer was compared to the accuracy of a powder camera, and it was determined that the diffractometer correctly identified the ratio within a range of 3% while the powder camera was accurate within a 20% range. This study showed that with an appropriate calibration curve, the HA/TCP ratio can be determined to a greater degree of accuracy using an x-ray diffractometer than by powder camera methods.
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  • 16
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    Journal of Applied Biomaterials 2 (1991), S. 29-35 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Anteior cruciate ligament (ACL) grafts made from expanded polytetrafluorethylene (ePTFE) were examined after failure (n = 7; 3 instabilities, 2 partial and 2 complete ruptures) to provide information about secondary fixation mechanisms via ingrowth of the different tissues. The ultrastructural evaluation clearly evidenced the existence of two main interface areas of ePTFE ACL-replacement: First, in areas without a dense cellular infiltrate there was interdigitating collagen producing a dense ePTFE-collagen network. Additionally, in a few areas of the graft/bone-tunnel interface a fibrous cartilage or bone regenerate could be demonstrated to be in contact with the prosthesis. Second, there was a dense infiltration of macrophages and multinuclear giant cells, partially containing birefringent material of implant origin, with and without a neosynovia-like reaction product, indicating a disturbance of tissue integration of the prosthesis. In areas of inflammation there was no bone development and only few collagen interdigitation with the graft material. This study provides further knowledge about mechanisms of secondary graft fixation due to tissue ingrowth. The interdigitation of collagen fibers and ePTFE filaments provides interfaces which should be at least partially resistant against load.
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  • 17
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We have developed a new poly(vinyl alcohol) hydrogel (PVA-H) of increased physical strength through a new manufacturing process. Its mechanical properties have been found to be preferable as a substitute for articular cartilage. To evaluate its biocompatibility as an artificial articular cartilage, a series of in vivo tests within the intraarticular, as well as the intramuscular, environment were conducted. Tissue reactions of cartilage, bone, synovium, and muscle to PVA-H were studied histologically. In the experimental group, in which PVA-H was implanted, inflammatory reactions of all of these tissues were very slight. In the control group, in which ultra-high molecular weight polyethylene (UHMWPE) was implanted, although tissue reactions of bone and muscle were as slight as in the experimental group, those of cartilage and synovium were somewhat more conspicuous. By way of these findings, the better biocompatibility of PVA-H was documented.
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  • 18
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    Journal of Applied Biomaterials 2 (1991), S. 153-159 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Glass plates of the chemical composition: CaO (29.0), SiO2 (31.0), Fe2O3 (40.0), B2O3 (3.0), P2O5 (3.0) in weight ratio were heated to 1050 °C at a rate of 5 °C/min and then cooled to laboratory temperature. The resulting glass-ceramic containing magnetite and wollastonite crystals showed high-saturation magnetization. The bonding ability of this new glass-ceramic to bone tissue was evaluated using rabbit tibiae, and compared with glass of the same composition. This glass-ceramic formed a Ca, P-rich layer on its surface and bonded tightly with bone within 8 weeks of implantation. However, the glass did not form this Ca, P-rich layer, nor had it bonded with bone at 25 weeks. The bone-heating ability of this glass-ceramic was investigated by applying a max. 300-Oe, 100-kHz magnetic field. The granules of the glass-ceramic filled in the rabbit tibiae heated the whole surrounding bone to more than 42 °C and maintained this temperature for 30 min. Bioactive ceramics reinforce the mechanical strength of bone tissue. Furthermore, this heat-generating bioactive glass-ceramic can be used for hyperthermic treatment of bone tumors.
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  • 19
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    Journal of Applied Biomaterials 2 (1991), S. 161-170 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In order to apply the extracorporeal shock wave lithotripter (ECWSL) technique to the loosening of the bone-cement interface for the extraction of the cement during revision arthroplasty it is essential to know the dose-response characteristics. The present study shows that the number of shocks needed to break the interface between a 2- and 6-mm-thick bovine femoral bone and bone cement is similar to the fatigue behavior of a material, that is, Log(N) = C(kV) + D, where N is the number of shock impulses, kV is the power setting of the lithotripter machine in kilovolts, and C and D are constants. Iso-pressure distribution of the traveling shock wave front through a simulated bone in a Plexiglass® tube using Fuji® pressure film showed quantitative pressure contours from which one can understand the effective area of shock wave and its distribution. The most effective area of the shock wave was about 1.5 cm in diameter at 23 and 25 kV with pressure at least 7.0 MPa which is more than sufficient to break the bone-cement interface in tension.
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  • 20
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Surgical sutures that are directly attached to the surgical needle ends are called swaged sutures. A forming tool has been used to split one-half of the wire diameter of cardiovascular needles that forms a channel or receptacle for the suture. With the advent of lasers, uniform holes can now be produced in the ends of small-diameter cardiovascular needles. An advantage of the laser-produced hole is that its outer circumference is smooth; the channel swage has a linear slit that interrupts its smooth outer circumference. A standardized reproducible test has been developed that quantitates the force required to pull the needle end through a synthetic membrane that simulates vascular tissue. A swage produced by a laser encountered significantly less drag forces than that noted with a comparable size channel swage of cardiovascular needles.
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  • 21
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    Journal of Applied Biomaterials 2 (1991), S. 187-208 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The morbidity associated with autogenous bone graft harvest and the recent concern regarding the transmission of live virus through use of allografts, have been the impetus for research into a variety of materials that could take the place of these standard materials for bone grafting. The positive results reported with various ceramics and/or bone derivatives suggest the possibility of a material with osteoconductive and/or osteoinductive properties for use with or in place of bone graft. This review discusses a variety of bone graft and bone graft substitute materials. Among the osteoconductive materials outlined are the hydroxyapatite and tricalcium phosphate ceramics as well as some reportedly osteoactive polymers. While osteoconduction is a favorable quality, much interest has focussed on the use of osteoinductive or osteogenic materials such as demineralized bone matrix or bone derivatives,that is, BMP, osteogenin, etc. It is increasingly apparent that these materials require a carrier vehicle for optimal expression of osteoactivity. Therefore, the review finishes with a comparison of the various materials suggested for use as carriers.
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  • 22
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    Journal of Applied Biomaterials 2 (1991), S. 241-242 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: It is common experience that carbon fiber braids, which are passed through osseous tunnels, are not incorporated by osteointergration. Rather, they are separated from the boy walls of the tunnels by a granulomatous-cicatrizing interface membrane. In the exceptional case, however, Bony ingrowth into the braid occurs without an intervening soft tissular layer. Bony ingrowth may be contingent on the stability of the carbon fiber braid within the osseous tunnel.
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  • 23
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    Journal of Applied Biomaterials 2 (1991), S. 231-239 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Bioactive glass powders, with a composition of SiO2-CaO-P2O5,have been successfully synthesized via a sol-gel process at considerably loer temperatures than required for conventional melting method. Bioactive glass powders made via conventional methods form an interfacial bond wih none when they are implanted. Bonding is correlated with the formation of a surface hydroxyapatite layer. This study examinded the formation of a hydroxyapatite layer in Tris-buffered solution as a function of SiO2 content of sol-gel derived powders. A FT-IRRS technique was used to monitor the formation of the hydroxyapatite on the surface of the powders. X-ray diffraction analysis and BET were also used to characterize the chemical and physical properties of the sol-gel derived bioactive powders. It was discovered that: (a) the rate of hydroxyapatite formation decreased wih increasing SiO2 content for powders whose SiO2 content was less than 90 mol%; (b) a hydroxyapatite film does not form for the powders whose SiO2 content is more than 90 mol%; (c) the SiO2 limit, beyond which the powders lost their bioactivity, was much higher for bioactive glass powders mad through sol-gel process (90%) than those made by conventional melting methods (60%). These results indicate that it is possible to significantly expand the bioactive composition range through microstructural control made possible by sol-gel processing techniques.
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  • 24
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    Journal of Applied Biomaterials 2 (1991), S. 243-250 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Classically, calcium hydroxide is used as a pulp capping agent in humans to form a dentinal bridge over vital dental pulp tissue. The aim of the present study was to determine whether synthetic hydroxyapatite could be used as a substitute. For this purpose, pulp capping with microsized hydroxyapatite (mean size = 38 nm ± 15 nm) was done under lacal anesthesia in 12 normal premolars, to be extracted for orthodontic purposes form 12 different young patients, having given their informed consent. Clinically, the healing was uneventful in all patients, having given their informed consent. Clinically, the healing was uneventful in all patients. Half of the teeth were extracted at 3 months and the other half at 6 months. The pulps were studied under light microscopy and under scanning and transmission electron microscopy using nondecalcified sections. In all cases, a continuous, well-calcified bridge was observed and no inflammatory cells were present in the residual pulp. In some cases denticles containing some synthetic hydroxyapatite crystals were found in the radicular pulp. The calcified bridge was made up by osteodentine and near the pulp tubular dentine with a layer of predentine and odontoblasts were noted. Odontoblastic processes were lacated in deninal tubules and the intertubular dentine showed interwoven calcified collagen fibrils and hydroxyapatite crystals with a mean length of 0.1 μm along their c axis.
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  • 25
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    Journal of Applied Biomaterials 2 (1991), S. 251-259 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A novel biotechnology is introduced by way of the successful synthesis of nanocrystalline Epstein-Barr virus (EBV) decoys having specific in vivo immunogenie activity. Assembled from ultrafine suface modified tin oxide and purified DNA-free isolated EBV envelope proteins, the decoys consisted of 〉150 nm units whose electophoretic mobilities were similar to whole EBV; whose outer coats were strongly immunoreactive with murine monoclonal anti-EBV antibodies; and which elicited immunospecific niutralizing anti-EBV antibodies in the rabbit. The development of this carier techonology for vaccine preparations is suggested.
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  • 26
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    Journal of Applied Biomaterials 2 (1991), S. 269-271 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 27
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    Journal of Applied Biomaterials 2 (1991) 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Journal of Applied Biomaterials 2 (1991), S. 1-12 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of this study was to evaluate a biodegradable poly(L-lactide) (P—L—LA) screw for osteosynthesis under a load-bearing condition. A proximal tibial osteotomy on 25 rabbits was fixed with a biodegradable screw made of P—L—LA. A follow-up study was done at 1, 2, 4, 8, and 16 weeks. In another 25 rabbits, the tibial osteotomy was fixed with stainless steel (SUS) screws of the same size as the P—L—LA screws with a similar follow-up period. Radiographic, histological, microradiographic, and oxytetracycline-labeling studies showed healing of the osteotomy within 4 to 8 weeks. The displacement of frag-ments and the mass of newly formed bone around the screws were measured by histomorphometric analysis. There was no significant difference in the displacement of the fragments in these two groups and new bone was more abundantly detected in the P—L—LA group than in the SUS group. Histologically, no inflammatory lesion was detected in either group. All osteotomies united without delay and the displacement was minimal, although no external support was applied and the rabbits were allowed to move freely after the operation. The results of this study suggest a possible use for a P—L—LA screw in the clinical treatment of human bone fractures.
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    Journal of Applied Biomaterials 2 (1991), S. 285-287 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Applied Biomaterials 2 (1991), S. 41-48 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: In vitro transmucosal permeation of (14C)-dibutyl phthalate [(14C)DBP], across intact mucosal hamster tissue compared to keratin-stripped mucosal tissue indicated no significant difference (p ≈ 0.069) in (14C)-DBP. However, significantly greater (p 〈 0.022) DBP was found to be concentrated in the keratin-stripped after a period of 6 h. The amount of (14C)-DBP permeating both tissues followed a similar linear increase for next 3 h. However, between 3 and 4 h, the rate of permeation through the untraumatized tissue significantly decreased. This was followed by a rapid linear increase for the next 3 h. In contrast, the cumulative amount of (14C)-DBP permeating the traumatized tissue showed a linear correlation (r = 0.995) over the 6-h period. A theoretical two-layer model was constructed to allow computer simulations of the (14C)-DBP permeation. It was indicated that an average diffusion coefficient for a single DBP molecule through the intact keratin layer would be ∼ 100 times less than through the remaining layer of the model. The model has enabled a possible explanation to be put forward, describing the role of the keratin layer in the permeation of plasticizer mucosal tissue.
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    Journal of Applied Biomaterials 2 (1991), S. 49-54 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Heat generated by tooth reduction and restoration procedures may be harmful to the pulp. Water spray during those procedures aids in maintaining lowered pulpal temperatures. A device that lowers intrapulpal temperatures has been developed and tested in an animal model. The animal's pulp chamber temperatures were lowered to 15.5°C and 12.4°C and maintained at those temperatures for 20 min. Histological examination disclosed no inflammatory reaction to the testing. Therefore, this device may aid in reducing the trauma of dental preparation procedures as well as other effects of lowered temperature on the biology of the dental pulp.
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    Journal of Applied Biomaterials 2 (1991), S. 55-56 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Applied Biomaterials 2 (1991), S. 57-58 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Applied Biomaterials 2 (1991), S. 63-65 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Applied Biomaterials 2 (1991), S. 61-62 
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  • 36
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    Journal of Applied Biomaterials 2 (1991) 
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  • 37
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    Journal of Applied Biomaterials 2 (1991), S. 59-60 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of my column is to provide readers with current information on biomaterials-related standards produced by both private groups and government agencies, and standards-related activities. Standards are descriptive documents given official status by their producers, and in the case of biomaterials, they are generally intended to provide formalized descriptions of (a) materials used in the construction of medical devices, (b) materials used directly in surgical repairs, (c) test methods to evaluate materials for such applications, and (d) methods for handling or processing such materials.Please consider this column not only a place to obtain biomaterials standards information, but also a place to submit news of biomaterials standards developments in order to get the information before the public. This invitation extends to members of all professional organizations and government agencies in the United States and abroad who are active in standards development and would like specific activities or standards publicized. I will present the information in this column to the extent that allotted space allows.And last, a caveat - since this is a column, it contains both factual information and opinions. I will make every effort to make it clear which is which. Also, as a frame of reference, please note that this column was written and submitted in November 1990.
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  • 38
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    Journal of Applied Biomaterials 2 (1991), S. 67-72 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Poly(vinyl alcohol) (PVA) microspheres impregnated with barium sulphate and methyl iothalamate, having diameters raning from 100 to 1500 μm were prepared by the glutaraldehyde cross-linking of an aqueous dispersion of PVA containing the radiopaques in paraffin oil using dioctyl sulfosuccinate (DOS) as the stabilizing agent and thionyl chloride as the catalyst. while the use of thionyl chloride allowed the formation of spherical, nonaggregatory beads, other catalysts such as magnesium chloride and hydrochloric acid gave rise to an agglomerated product. The radiopaques were found to be firmly trapped inside the microspheres as they did not leach out on prolonged standing in water, on sonication, or on steam sterilization. Microspheres with pores and channels were also made by incorporating a fine powder of methyl methacrylate along with barium sulphate during their preparation and washing out the polymer after the microspheres were formed. The porous nature of such microspheres was confirmed by transmission electron microscopy (TEM). Microspheres containing the radiopaques exhibited hydrophilicity, swelling ability, and compressibility to a significant extent. the radiopaque nature of the microspheres was confirmed by their x-ray images. In vitro tests using heparinized calf blood showed that the microspheres were nonhaemolytic in nature. These microspheres may find application as radiopaque emboli in particulate embolization.
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    Journal of Applied Biomaterials 2 (1991), S. 95-99 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: One-hundred-fifteen retrieved, porous-coated, uncemented patellar knee components of a wide variety of designs were examined for type and amount of tissue ingrowth and for wear and creep of the polyethylene-articulating surface. Examples of well-fixed patellar components of all designs presented regions of bone ingrowth independent of pore size, number of fixation pegs, and the presence or absence of coating on the pegs. Polyethylene breakdown, including delamination, pitting, subsurface cracking, and separation from the metal backing, was common. Comparative analysis indicates that solutions exist and include increasing congruency and polyethylene thickness and eliminating metal fixation buttons.
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    Notes: New and used polypropylene tailstrings from the Copper 7 (Cu-7) intrauterine device were examined by a combination of analytical techniques. Optical microscopy, scanning acoustic and electron microscopy, x-ray diffraction, energy dispersive x-ray analysis, and chemical etching were employed to elucidate both the surface and interior morphology of new Cu-7 tailstrings. Tailstrings removed from women following varying periods of use were investigated with optical microscopy, scanning and transmission electron microscopy. In addition, a subset of the used tailstrings were cultured to identify the types of microorganisms associated with them. Our findings show that unused Cu-7 tailstrings are in various stages of degradation owing to a combination of factors which include the high-draw ratio employed during manufacturing, the method of packaging, and the use of a particulate colourant. Furthermore, it is evident that used Cu-7 tailstrings undergo major deterioration while in situ because of the unfavorable interactions between the highly drawn polypropylene and the physiological environment. These results indicate that the polypropylene tailstrings as manufactured for use with the Cu-7 IUD fail to meet accepted design criteria for biomedical implants.
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  • 41
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    Journal of Applied Biomaterials 2 (1991), S. 109-113 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Initial rigid fixation is essential for bone ingrowth into a porous-coated prosthesis. In this study, the amount of micromotion between a cut tibial surface and a custom tibial base-plate mounted with various types of screw fixation was measured. Motion transducers were placed at the corners of the baseplate to detect liftoff and subsidence. Central and eccentric loads were then applied. The variables tested included screw number and position, as well as screw length and type of bone purchase.A four-screw peripheral configuration had less micromotion than a three-screw triangulated configuration, and both had less micromotion than a two-screw central condyle configuration. Long screws with cancellous purchase and screws with cortical purchase had less micromotion than short screws with cancellous purchase.These results indicate that important variables which contribute to the initial rigidity of a cementless tibial implant using screw fixation include screw number, configuration, length, and type of bone purchase.
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    Notes: In this paper we have reviewed the feasibility of using a shock wave lithotripter to loosen the interface between the bone and acrylic bone cement for revision arthroplasty. We have reviewed the physics of shock wave and its applications in medicine, especially its interaction with tissues. The calculations show that the energy is greatly reduced at the interface both in the soft tissue-bone interface and cement-bone interface. On the other hand, a tensile and compressive pressure can be operated at the cement-bone interface that can cause the interface to break if the pressure exceeds the tensile strength of the cement-bone interface.Subsequent papers will deal with in vitro and in vivo application of the shock wave in the treatment of the cement-bone interface in order to weaken it and consequently for easier extraction of bone cement from the intramedullary canal.
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    Journal of Applied Biomaterials 2 (1991), S. 127-131 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: National population-based estimates on the magnitude and distribution of orthopedic implant devices in the United States have not been available to date. The Food and Drug Administration's Center for Devices and Radiological Health (FDA/CDRH) collaborated with the Centers for Disease Control's National Center for Health Statistics (CDC/NCHS) in the design and conduct of a nationwide medical device implant survey to generate the first national population-based prevalence estimates of orthopedic implant devices. A Medical Device Implant Supplement to the 1988 National Health Interview Survey was administered in personal household interviews to a national sample of 47,485 households, which included 122,310 individuals.An estimated 6.5 million orthopedic implants were in use in the general US population in 1988, including 1.6 million artificial joints and 4.9 million fixation devices. As a group, orthopedic implants comprised nearly half of all medical device implants in use, 43.4%. The majority of artificial joint recipients were 65 years of age or older, white, and male. the majority of fixation device recipients were less than 45 years of age, white, and male. The limitations and strengths of these population-based estimates are discussed.
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    Journal of Applied Biomaterials 2 (1991), S. 133-139 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The field of biomaterials has grown rapidly over the last three decades in the academic, industrial, and regulatory sectors. Beginning as a research thrust, which led to courses at a few universities, biomaterials education has evolved into distinct curriculum in over 60 institutions in the United States and Canada alone.Rapid growth, however, can cause problems. In an effort to determine the present status and future needs in each sector, as well as begin to assess if the needs of industry are being met by present academic programs, two surveys were sent out.As shown by the two surveys, academic programs have been increasing in both size and quality while industry has also been expanding, as indicated by the many small companies involved in biomaterials. The shift toward graduate programs is in keeping with the perceived educational needs of potential employers. The majority of academic programs appear to be providing the training and coursework desired by employers. Further information, however, is needed to determine if the number of graduates trained in biomaterials is adequate, or in fact excessive.It is, therefore, recommended that a more comprehensive survey, sent to the biomaterials companies listed in the FDA registry, be undertaken. In addition, a survey to each academic program that addresses hiring of recent graduates would also be beneficial. It does appear that certain standards for curricula could be agreed upon, although the field has probably not evolved sufficiently for accreditation or professional registration to be addressed yet.
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    Journal of Applied Biomaterials 2 (1991), S. 143-145 
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    Journal of Applied Biomaterials 2 (1991) 
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    Journal of Applied Biomaterials 2 (1991), S. 141-142 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The purpose of my column is to provide readers with current information on biomaterials-related standards produced by both private groups and government agencies, and also on standards-related activities. Standards are descriptive documents given official status by their producers, and in the case of biomaterials, they are generally intended to provide formalized descriptions of (a) materials used in the construction of medical devices, (b) materials used directly in surgical repairs, (c) test methods to evaluate materials for such applications, and (d) methods for handling or processing such materials.Please consider this column not only a place to obtain biomaterials standards information, but also a place to submit news of biomaterials standards developments in order to get the information before the public. This invitation extends to members of all professional organizations and government agencies in the United States and abroad who are active in standards development and would like specific activities or standards publicized. I will present the information in this column to the extent that allotted space allows.And last, a caveat-since this is a column, it contains both factual information and opinions. I will make every effort to make it clear which is which. Also, as a frame of reference, please note that this column was written and submitted in March 1991.
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    Journal of Applied Biomaterials 2 (1991), S. 147-152 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Ultrastructural properties of precipitated apatites were characterized before and after sintering at 900 and 1250 °C using high resolution transmission electron microscopy. The apatite crystals were oriented with respect to the electron beam so that the crystals could be examined in relation to the high resolution images of the (001) and (100) planes. The ultrastructural properties were found to be affected by sintering temperature. Numerous lattice defects, including atomic vacancies, dislocations and two types of grain boundaries were observed. In addition, a new type of three-dimensional lattice defect was frequently observed in the apatites sintered at 900 °C. This type of lattice defect has the character of a hexagonal parallelipiped void, probably resulting from an aggregation of atomic vacancies. Calcium phosphate ceramics (hydroxyapatite and tricalcium phosphate) prepared by precipitation and subsequent sintering to temperatures above 1100 °C are presently used as bone grafts. The amount and kind of defects such as those observed in this study have significant implications on the extent of the degradation of these materials in vivo.
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    Journal of Biomedical Materials Research 25 (1991) 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 25 (1991), S. 23-38 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Medicine , Technology
    Notes: Variable alumina quantities were added to two types of calcium phosphate materials-hydroxyapatite ceramics with Ca/P = 1.67 and calcium metaphosphate glass with Ca/P = 1-in order to increase their mechanical properties. Raman spectroscopy shows that alumina interacts with the phosphate group of these materials, while thermomechanical analysis shows that their elastic modulus has a value similar to that of bone. Histological sections demonstrate that the surface in close contact with ceramic materials shows a good integration between bone and biomaterial. All ceramic specimens are penetrated by well-stained, presumably glycoprotein, matrix, that consistently forms a thin network in close contact with the implant. After 6 weeks bone growing on both ceramic and glass shows signs of maturation with a lamellar structure and an apparently normal mineralization. In the case of the glass, inside this newly formed bone, were often observed two layers, the internal one showing a well defined lamellar structure.
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    Journal of Biomedical Materials Research 25 (1991), S. 67-84 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Investigations are reported on the composition of protein layers adsorbed from plasma to various modified polystyrene resins. As well as polystyrene itself, polystyrene bearing sulfonate groups in the benzene rings, and polystyrene sulfonate in which the sulfonate groups were converted to amino acid sulfamide, were investigated. Some of these resins were shown in previous work to have anticoagulant properties. To study the adsorption of proteins from plasma, the resins were exposed to citrate anticoagulated human plasma for 3 h. Adsorbed proteins were then eluted sequentially by 1M Tris buffer and 4% SDS solution, and examined by SDS-PAGE. The gel patterns were similar on all resins except polystyrene. From the MWs of the gel bands, the major protein component appeared to be fibrinogen. Smaller amounts of plasminogen, transferrin, albumin, and IgG were also present. In addition, Ouchterlony immunoassay of the eluates from one resin gave positive identification of complement C3, fibronectin, IgG, and IgM. Many other minor gel bands remain unidentified. A consistent finding for all resins was the presence of plasmin-type fibrinogen degradation products though the amounts varied with resin type. It is concluded from this (and from experiments showing FDP formation when fibrinogen was adsorbed to the resins, from buffer containing a trace of plasminogen) that the functional groups in these materials promote the adsorption of plasminogen and its activation to a plasmin-like molecule. It appears from the substantial quantities of fibrinogen adsorbed to these materials after 3 h exposure to plasma that the Vroman effect (giving transient adsorption of fibrinogen) is not operative on these materials. It is hypothesized that specific interactions occur between fibrinogen and sulfonate groups.
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    Journal of Biomedical Materials Research 25 (1991), S. 177-183 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 25 (1991), S. 213-221 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Polyfunctional silanes were designed to promote the formation of a stable multisilane layer on the silica surface. The hydrolytic stability of polyfunctional silanes at the interface between silica and polymeric resin was investigated using conventional tensile testing. The specimens were immersed in boiling water and a decrease was observed in the tensile bonding strength of polymeric resin against the silane-treated silica surface as the immersion time increased. The failure mechanism changes from cohesive failure of the matrix resin to failure of the interface. The time necessary to start the interfacial failure is dependent on the silane concentration in the treating solution and the number of silicone functional groups within the silane molecules. The silane with two silicone functional groups is more stable at the interface between silica and polymeric resin than those which have mono- or trisilicone functional groups.
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    Journal of Biomedical Materials Research 25 (1991), S. 243-254 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Two types of liquid crystal (LC)-entrapped membranes, (a) polymer alloyed membranes and (b) LC-adsorbed membranes, were investigated for the purpose of developing the drug delivery systems (DDS) with thermal stimuli responsing. Polymer alloyed membranes were obtained by polymerizing acrylic monomers in presence of LC and LC-adsorbed membrane were obtained by adsorbing LC into porous hydrophobic polymer membrane. It was made clear from the indomethacin permeation experiments below and above the gel-liquid crystal phase transition temperature of the LC that the extent of thermo-sensitivity for LC-adsorbed membranes was greater than that for the alloyed membrane. The permeability ratio (38°C vs. 32°C) was found to be about 120 with the LC-adsorbed membrane. It was suggested from the results that the LC-adsorbed membrane was one of the useful candidates as a thermo-responsive system for DDS.
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    Journal of Biomedical Materials Research 25 (1991), S. 277-280 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The results of these in vivo experiments show that bovine pericardium can undergo calcification without direct contact with tissue. It is clear that the direct interaction of cells with implanted samples both promotes and accelerates the process of calcification. Moreover, dietary calcium supplements, calcium chloride and vitamin D can intensify the rate and extent of this process.
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    Journal of Biomedical Materials Research 25 (1991), S. 341-356 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: A series of segmented polyurethanes (SPUs) containing various polyol soft segments was prepared and their resistance to oxidative degradation was investigated after aging in AgNO3 solution. The SPU with the polyether soft segment showed a large reduction in mechanical strength after exposure to the oxidative environment. Surface cracking was often observed for these specimens. XPS measurements revealed that scission of the ether linkage occurs upon oxidation. The oxidative resistance of SPUs containing aliphatic hydrocarbon soft segments was significantly improved over the poly(tetramethylene oxide) (PTMO) based polyurethane.
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    Notes: Relatively low-molecular-weight copolyesters of glycolic acid (GA) with lactones such as γ-butyrolactone (BL), δ-valerolactone (VL), and ∊-caprolactone (CL) were synthesized by copolycondensation without catalysts. The resulting copolyesters are intended as carriers for drug delivery systems. Copolyesters with approximately 85 mol% GA (number-average molecular weight (Mn): 2900 ± 100) are crystalline and solid and show a parabolic-type in vivo degradation pattern. The in vivo degradation of amorphous-pasty poly (GA/CL) (approximately 50/50 mol%) changed from parabolic-type to lineartype to S-type pattern as their molecular weight increased. A luteinizing hormonereleasing hormone agonist, D-Leu,6 desGly10 -LHRH ethylamide monoacetate (LHRH agonist), was incorporated into small cylinders with these copolyesters. An initial burst of LHRH agonist was observed for cylinders prepared with parabolic-type degrading copolyesters, in contrast to a marked delay in LHRH agonist release for cylinders prepared with S-type degrading copolyesters. The resulting daily dose of drug was maintained an approximately constant, though decreasing stepwise with time. For example, the daily amount of LHRH agonist released in vivo from a cylinder prepared with poly(GA/CL) (50/50 mol%; Mn = 4500) was 61 ± 39 μg/day throughout an experimental period of 10 weeks with a corresponding pharmacological effect on the rat prostate.
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    Journal of Biomedical Materials Research 25 (1991), S. 557-558 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 25 (1991), S. 577-588 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Two types of liquid crystal (LC)-immobilized membranes were prepared by a soaking method and sandwich method to control the permeation of indomethacin, as a model drug, in response to local and systemic fever. Monooxyethylene trimethylolpropane tristearate (MTTS) was used as a model LC because it has a gel-liquid crystal phase transition temperature near the body temperature, 39-40°C in phosphate buffered saline (pH 7.4). Two porous polypropylene (PP) membranes were soaked into 20% MTTS chloroform solution in the soaking method, and two PP membranes were poured with the melted MTTS and pressed in the sandwich method. Thermo-response efficacy of the soaked membrane was dependent upon the content of MTTS in MTTS membrane, and the MTTS content above the void volume of PP membrane (38%) was needed for high efficacy. On the other hand, the sandwich membrane exhibited higher thermo-response efficacy than the soaked membrane, because more LC was embedded in the pores of sandwich membrane than that of the soaked membrane. The sandwich membrane permeation of indomethacin was sharply controlled by temperature changes between 32 and 38°C.
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    Journal of Biomedical Materials Research 25 (1991), S. 609-619 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The present study was designed to ascertain if dynamic ionic matrices that mimic the mineralization front could be used as active scaffolds for bone repair. Dentinal phosphophoryn calcium salts were extracted from unerupted bovine dentin using chatopic buffers and EDTA. The phosphophoryns were subsequently isolated following precipitation with CaCl2. The phosphophoryn-Ca+2 salts were then mixed with pepsin solubilized bovine skin collagen and lyophilized into hardened sponges. Three groups of 4 beagle dogs were employed such that one leg served as an experimental test site for a mechanical wound, while the contralateral leg served as a control. Animals were sacrificed at 1, 3, and 6 month intervals. The test specimens were harvested, fixed, and processed for routine histology, examined with image histomorphometric analysis, and scored. Tabulation of these data indicated that phosphophoryn-Ca+2-collagen enhances the repair of mechanically formed osseous defects in the distal femur of beagle dogs. This enhanced rate of bone repair was manifest by earlier filling of bony voids with osteoid and trabecular bone. Eventually, this process was followed by recortification of the surface defects. These data suggest that components derived from a mineralization front may influence bone formation in unicortical defects within long bones.
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    Journal of Biomedical Materials Research 25 (1991), S. 651-666 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Growth rates of rat tendon fibroblasts cultured in a three-dimensional carbon fiber matrix were compared with those of cells cultured on standard flat culture plates. The carbon fiber has been used as a tissue scaffold for tendon and ligament repair in animal and clinical studies. While cell growth on the culture plates appears to follow a growth curve containing a lag phase, a log phase, and plateau phase of growth, cell growth in the fiber matrix was characterized by a suppressed log phase of growth. SEM and cytotoxicity studies indicated that this effect was not caused by growth-inhibiting or cytotoxic substances from the carbon fiber. While we cannot rule out the possibility that cell growth was influenced by the surface chemistry of the carbon substrate, evidence from this and other studies suggests that the observed effect was caused by a lack of readily available surface area for cell attachment and growth on the small fibers. Because cell colonies growing on individual fibers are limited (at least in theory) to growing in two directions only, they enjoy limited opportunities for cell migration and growth- in contrast with cell colonies on flat culture plates. These results suggest fundamental differences in the mechanisms controlling cell growth on planar vs. three-dimensional fiber substrates.
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    Journal of Biomedical Materials Research 25 (1991), S. 697-697 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 25 (1991) 
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    Journal of Biomedical Materials Research 25 (1991), S. 875-887 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Polyvinyl alcohol (PVA)-coated polyethylene tubing, with or without immobilized heparin, caused severe thrombocytopenia and enhanced the production of new platelets when inserted in a chronic arteriovenous shunt in canines. A similar length of uncoated polyethylene tubing neither lead to thrombocytopenia nor significantly enhanced platelet regeneration, relative to the shunt only without a test section. Platelet regeneration was monitored by the malondialdehyde assay, which was assumed to make a distinction between “new” and “old” platelets. This distinction was combined with the platelet count values to enable calculation of the cumulative consumption curve and the initial fractional consumption rate in the presence of a non constant platelet count. The resulting initial fractional consumption rates were: 34%/day for PVA, 20.5%/day for polyethylene, and 18%/day for the shunt only blank.
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    Journal of Biomedical Materials Research 25 (1991) 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 25 (1991), S. 1019-1030 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The calcium phosphate formation at the surface of bioactive glass was studied in vitro. Glass rods and grains were immersed in different aqueous solutions and studied by means of scanning electron microscopy and energy dispersive x-ray analysis. Surface morphological changes and weight loss of corroded grains were monitored. In-depth compositional profiles were determined for rods immersed in the different solutions. The solutions used were tris-buffer (trishydroxy-methylaminomethane + HCl), tris-buffer prepared using citric acid (trishydroxy-methylaminomethane + C6H8O7·H2O), and a simulated body fluid, SBF, containing inorganic ions close in concentration to those in human blood plasma. It was found that the calcium phosphate formation at the surface of bioactive glass in vitro proceeds in two stages. When immersing the glass in tris or in SBF a Ca,P-rich surface layer forms. This accumulation takes place within the silica structure. Later, apatite crystals forming spherulites appear on the surface. The Ca/P-ratio of initially formed calcium phosphate was found to be about unity. It is proposed that this is due to bonding of phosphate to a silica gel. The surface is stabilized, i.e., leaching is retarded, by the rapid Ca,P-accumulation within the silica structure before apatite crystals are observed on the surface. It is proposed that the initially formed calcium phosphate is amorphous and that the crystallization is initiated within the silica gel. The crystallizing surface provides nucleation sites for extensive apatite formation on the glass surface. In the presence of citrate no Ca,P-accumulation occur at the glass surface, but soluble Ca-citrate complexes form. By comparing the weight loss during corrosion in tris with that in the calcium and phosphate containing SBF, it is possible to establish whether the glass can induce apatite formation at its surface or not.
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    Journal of Biomedical Materials Research 25 (1991), S. 1045-1068 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The effect of different treatments for preparing implant materials was examined by scanning electron microscopy and by contact angle measurements. The materials examined were Ti6Al4V alloy, Co-Cr-Mo alloy, Al2O3, and synthetic hydroxyapatite. Samples were prepared with solid or porous surfaces of these materials. These were detergent-cleaned and then either autoclaved (steam sterilization), radiationsterilized, nitric acid-etched, or plasmacleaned. The results of wettability studies indicated marked changes in surface energy corresponding to the different preparation methods, and differences in surface morphology were also observed. These differences could have significant consequences on in vivo implant behaviour as mediated by tissue-implant interactions.
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    Journal of Biomedical Materials Research 25 (1991), S. 1119-1131 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The inflammatory reaction to implanted biomaterials often compromises the clinical usefulness of implantable devices. Dexamethasone, an anti-inflammatory agent, acts on macrophages to decrease production of inflammatory mediators, and on mast cells to prevent degranulation. Systemic administration of dexamethasone (dms) in rats decreases the tissue reaction to intraperitoneally implanted vinyl chloride-acrylic copolymer capsules. Local release of even smaller amounts of dms from a polymeric substrate placed inside an acrylic copolymer capsule may control the tissue reaction while avoiding the undesirable side effects of systemic treatment. Such a system also allows investigation of the local effect of soluble molecules on tissuematerial interactions without altering the surface properties of the implant or adding the effect of a releasing material. In the present study, we investigated the effect of dms released from ethylene vinyl acetate (EVAc) rods placed in acrylic copolymer capsules and implanted in the peritoneal cavity of rats. In vitro the release of dms from EVAc rods was quasilinear for 5 weeks. When implanted intraperitoneally into rats, polymer capsules containing EVAc/dms rods generated a tissue reaction that was significantly thinner and featured fewer fibroblast and collagen layers than that around capsules containing pure EVAc rods at all time points studied. The tissue reaction layer was also thinner than that previously described in rats treated systemically with dms. The trabeculae of implants with dms-loaded EVAc rods contained significantly more intact mast cells is involved in the tissue reaction to intraperitoneal polymer implants.
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    Journal of Biomedical Materials Research 25 (1991), S. 1169-1181 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A new type of biocompatible copolymer comprising small fragments of heparin, (octa- to dodecasaccharides) copolymerized with a synthetic monomeric component, viz. acrylamide, has been prepared. The heparin fragments are produced by enzymatic or chemical means and are copolymerized, directly or after suitable derivatization, with acrylamide as the major polymerizable component. The polymeric material incorporates the heparin segments as pendant moieties such that their essential functional groups and structural features for specific binding with the selective serine protease coagulation factor inhibitor antithrombin III are preserved. An important feature of this copolymer is its biocompatibility which relates specifically to its antithrombotic and antithrombogenic activity derived from those of heparin fragments. The biological activity of heparin fragments and copolymers thereof are determined in terms of APTT and anti-Xa activity, their antithrombotic potential being expressed as a ratio of anti-Xa activity to APTT. The copolymers reported have biological activities similar to equivalent amounts of respective heparin fragments, and show higher antithrombotic activity compared to intact heparin or commercially available low-molecular-weight heparin (4,000-6,000 Da).
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    Journal of Biomedical Materials Research 25 (1991), S. 725-739 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Four materials based on a single poly(etherurethane) (PEU) prepared from MDI and PTMEG but differing in additives were studied in the cage implant systm. The two additives studied were Santowhite powder at the 1% level and Methacrol 2138F 5%. Methacrol 2138F appeared to be immiscible with the base PEU and was dispersed in discrete domains about 0.5-μm in size. The retrieved PEU specimens were also cleaned and examined in the optical and scanning electron microscopes, and the size and density of adherent foreign body giant cells (FBGCs) were measured at implantation times up to 10 weeks. Methacrol 2138F had no effect on the density, coverage or size distribution of adherent FBGCs, but leaching of Methacrol 2138F was considered to be responsible for extensive pitting of the PEU surface. On the other hand, Santowhite powder appeared to inhibit formation of FBGCs, and while surface cracking and flaking were observed as early as 3 weeks postimplantation on some PEUs, the Santowhite powder effectively inhibited surface cracking and flaking up to the longest implantation time studied.
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    Journal of Biomedical Materials Research 25 (1991), S. 1287-1301 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Suburothelial injections of particulate poly(tetrafluoroethylene) (PTFE) is becoming a widely accepted treatment for a number of urological disorders. Because little is known about the long-term histologic morphology of the injection site, this animal study was performed. Three populations, each consisting of two mongrel dogs, five New Zealand White rabbits, and 10 BALB/c mice, were injected with poly(tetrafluoroethylene) particulate in a glycerine carrier (Polytef Paste) and were followed for a period of 1 week, 3 months, 6 months, and 1 year. Mice received one subcutaneous dorsal injection each, rabbits received two subareolar injections each, and dogs received three subareolar injections each in addition to two periurethral injections. Histologic examination of the biopsy sites revealed a persistent chronic inflammatory reaction with progressive growth of the involved tissue volume. In addition to giant cells and macrophages, lymphocytes became apparent at 3 months and constituted up to 40% of the cellular infiltrate by 1 year. Plasma cells were also noted at the 1-year period in the rabbit model. The progressive growth of the inflammatory pseudotumors evoked by injected PTFE may compromise the long-term safety of certain urological procedures involving particulate PTFE.
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    Journal of Biomedical Materials Research 25 (1991) 
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    Journal of Biomedical Materials Research 25 (1991), S. 1363-1370 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Previous studies on surface structural changes in vitro as well as in vivo of bioactive A-W-type glass-ceramics and Bioglass-type glasses showed that the essential condition for glasses and glassceramics to bond to living bone is formation of a bonelike apatite layer on their surfaces in the body. Gross et al., however, had explained the bone-bonding mechanism of Ceravital-type apatitecontaining glass-ceramic without mentioning formation of the surface apatite layer. In the present study, apatite formation on the surface of one of Ceravitaltype glass-ceramics was investigated in vitro as well as in vivo. An apatitecontaining glass-ceramic of the composition Na2O 5, CaO 33, SiO2 46, Ca(PO3)2 16 wt%, which was named KGS by Gross et al., was soaked in an acellular simulated body fluid which had ion concentrations almost equal to those of the human blood plasma. The same kind of glassceramic was implanted into a rabbit tibia. Thin-film x-ray diffraction, Fourier transform infrared reflection spectroscopy, and scanning electron microscopic observation of the surfaces of the specimens soaked in the simulated body fluid showed that Ceravital-type glass-ceramic also forms a layer of carbonate-containing hydroxyapatite of small crystallites and/or a defective structure on its surface in the fluid. Electron probe x-ray microanalysis of the interface between the glassceramic and the surrounding bone showed that a thin layer rich in Ca and P is present at the interface. These findings indicated that Ceravital-type glassceramics also form the bonelike apatite layer on its surface in the body and bond to living bone through the apatite layer.
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    Journal of Biomedical Materials Research 25 (1991), S. 1431-1442 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A cage implantation technique has been adopted in a rabbit animal model to investigate the biocompatibility of an aliphatic crosslinked polyurethane based on hexamethylene diisocyanate (HDI). In this study, four cages are represented; the cage containing the candidate polyurethane material, biomedical grade polyurethane (Tecoflex), the commercial grade polyvinylchloride (PVC), and an empty cage which were implanted subcutaneously in rabbits. Exudates were aspirated from these cages at 4, 7, 14, and 21 days postimplantation. Exudates were analyzed for variations in proteins, cell counts, and extracellular enzymes. Results with the four types of cage implants showed that the candidate polyurethane caused an inflammatory response comparable to that caused by medical-grade Tecoflex and the empty cage control.
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    Journal of Biomedical Materials Research 25 (1991), S. 1481-1494 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In an attempt to develop biodegradable polymers which can be shaped in situ and adhere to living tissues, we synthesized esterurethane prepolymers which can be cured upon contact with water in living tissues. First, D,L-lactide polymerization or D,L-lactide-∊-caprolactone (50:50) co-polymerization was carried out using ethylene glycol or poly(ethylene glycol) as initiator to obtain hydroxyl-terminated biodegradable polyesters. They were then reacted with an excess of diisocyanate such as hexamethylene diisocyanate, toluylene diisocyanate, and diphenylmethane diisocyanate to introduce a reactive isocyanate group to both of the end groups of the polyesters. The isocyanate-terminated prepolymers could be cured in the presence of water and the cured polymers were degraded by hydrolysis both in vitro and in vivo. It was found that the presence of appropriate amounts of hydrophilic units in the main chain was essential for giving a high curing rate and a high degradation rate for the biodegradable urethane prepolymers. The tissue responses to the cured polymers were not severe.
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    Journal of Biomedical Materials Research 25 (1991), S. 1249-1257 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Polyurethane fibers were synthesized and characterized by IR, 1H NMR, DSC, and GPC. Their properties as fiber were compared with commercially available sutures of polypropylene, polyamide, polyester, and silk.
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    Journal of Biomedical Materials Research 25 (1991), S. 1317-1320 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 25 (1991), S. 1325-1337 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Materials to enhance cell adhesion were synthesized by surface integration of peptide, Arg-Gly-Asp-Ser(RGDS), which is an active-site sequence of cell-adhesive proteins. Polystyrene film was glowdischarged and graft-copolymerized with acrylic acid. Then the peptide was immobilized to the poly(acrylic acid) grafts by using water-soluble carbodimide. The cell-adhesive activity of the RGDS-immobilized film increased with increasing amount of immobilized peptide, and approached the activity of fibronectin(FN)-immobilized film. The RGDS-immobilized film was more stable against heat treatment and pH variation than the FN-immobilized film. In addition, the RGDS-immobilized film enhanced cell growth more strongly than the FN-immobilized film.
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    Journal of Biomedical Materials Research 25 (1991), S. 1397-1407 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Protein adsorption from human plasma was investigated on phospholipid polymers, poly (2-methacryloyloxyethyl phos-phorylcholine (MPC)-co-n-butyl methacrylate (BMA)) or glass by radioim-munoassay and immunogold labeling techniques. In the present studies the focus was to determine the composition and distribution of proteins at the surface of these materials after contact with human blood plasma. On all materials, protein adsorption was detected and included identification of albumin, IgG, fibrinogen, fibronectin, Hageman factor (factor XII), factor VIII/von Willebrand factor, high-molecular-weight kininogen (HMWK) and the complement protein C5. The amount of protein adsorbed decreased with an increase in MPC composition and appeared to adsorb to the surfaces in a uniform and evenly distributed manner. Therefore, we suggest that MPC moieties play an important role in suppression of protein adsorption. From these findings, it is concluded that the reduction of protein adsorption at the blood contacting surface of phospholipid polymers may result in the inhibition of thrombus formation.
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    Journal of Biomedical Materials Research 25 (1991), S. 1371-1395 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Polyurethanes chain extended with N,N-bis (2-hydroxyethyl)-2-aminoethanefulfonic acid (BES) were synthesized. The effect of the sulfonic acid group on the polymers' bulk, surface, and bloodcontacting properties was evaluated by comparing the BES-based polymers with polyurethanes based on N-ethyldiethanolamine (EDEA). In addition, the effect of soft-segment polarity was addressed by comparing polyurethanes based on polyetetramethylene oxide (PTMO) (MW = 1000) with polymers based on polyethylene oxide (PEO) (MW = 1000). The EDEA control samples had physical properties similar to a viscous fluid. The presence of the sulfonic acid group dramatically enhanced the degree of microphase separation and the mechanical strength of all the polymers. The more polar PEO soft segment resulted in polymers which were more phase mixed than the PTMO-based polyurethanes. Surface characterization studies revealed that in vacuum, all the surfaces were enriched in the polyether soft-segment phase. After 24-h equilibration in water, all the surfaces had similar surface polarities independent of the SO3H content. The canine ex vivo blood-contacting results showed that the sulfonic acid group in the PTMO-based polymers significantly reduced the number and activation of the adherent platelets. Fibrinogen deposition, however, increased with increasing sulfonic acid content. In contrast, platelet and fibrinogen deposition on the sulfonic acidcontaining PEO-based polymers was greatly enhanced.
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    Journal of Biomedical Materials Research 25 (1991) 
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  • 82
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The biocompatibility of nine different materials, including positive and negative references, 4 polyurethane based and 3 latex based materials was investigated by (1) cytotoxic assay using V79 Chinese hamster cells, (2) the thickness of inflammatory layer at 3 and 7 days after intramuscular implantation test, and (3) the course of the blood flow in tissue reaction around subcutaneously implanted materials using Laser Doppler Flowmetry (LDF) over 14 days following implantation. In addition, for some materials, different modes of sterilization were compared. Although the three methods explore different reactive systems, the material ranking obtained was highly similar for the three methods, suggesting a relative accuracy between them. For one latex however, an absence of cytotoxic effect in culture and a highly intense response by LDF investigation of the same order of magnitude as for the positive reference implant suggest that bioincompatibility may result from the material itself and cannot be exclusively investigated by the leaching of toxic components.
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The ultra-high-strength, self-reinforced (SR) absorbable polymeric composites, consisting of reinforcement elements, like fibers, and of matrix polymer which have the same chemical element composition as reinforcement, were defined. A method to manufacture self-reinforced, absorbable polyglycolide (SR-PGA) rods of polyglycolide sutures (Dexon) by sintering them partially together at elevated temperature and pressure was presented. The rods with nominal diameters of 1.5 mm, 2.0 mm, 3.2 mm, and 4.5 mm showed initial bending modulus and strength values of 8-15 GPa and 220-405 MPa, respectively. Their initial shear strengths were 165-255 MPa. The smallest rods (diam. 1.5 mm) lost their mechanical strength after implantation in the subcutis of rabbits in 4-5 weeks while the thickest rods retained their strength over 8 weeks. The ultra-high-strength SR-PGA rods were concluded to be suitable for fixation of cancellous bone fractures, osteotomies, and epiphyseal plate fractures where the fixation is not exposed to excessive mechanical stresses and where the loads are predominantly of a shear nature.
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    Journal of Biomedical Materials Research 25 (1991), S. 99-115 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Poly(sodium vinyl sulfonate) (PVS) was found to be 1/14 times as active as heparin in inducing the conformational change and activation of antithrombin III. The conformational change of antithrombin III was investigated in terms of the intrinsic fluorescence of tryptophan residue, the extrinsic fluorescence using 1,6-diphenyl-1,3,5-hexatriene as fluorescent probe, and Fourier-transform infrared spectroscopy. It was evident in the experiment using 2,4,6-trinitrobenzene sulfonate that PVS elicited the activity of antithrombin III by interacting with amino groups of the protein as does heparin.Sodium vinyl sulfonate was graft-polymerized onto polyetherurethane (PEU) film that was treated with glow discharge in advance. PVS-grafted PEU film adsorbed antithrombin III easily and, like ungrafted PVS, induced conformational change and activation of antithrombin III. However, the mechanism of interaction of the PVS graft with antithrombin III did not seem to be completely the same as that of ungrafted PVS in solution.
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  • 85
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    Journal of Biomedical Materials Research 25 (1991), S. 117-128 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The effects of massive administration of bioactive ceramic powder (Bioglass (45S5), Ceravital (KGS), apatite-wollastnite containing glass ceramics (A-W GC), and hydroxyapatite (HA)), by intraperitoneal (IP), intramuscular (IM), or subcutaneous (SC) injection in Balb/c mice were examined in this investigation. Alumina, Silica Glass (SG), and A-W-A1 (containing the same amount of crystal as A-W GC and 6.3% Alumina) were used as nonbioactive controls. The particle size of each material injected was smaller than 44 μm. In addition to the above, two more sizes (smaller than 105 μm and smaller than 255 μm) of A-W GC powder, and a 1 × 1 × 0.2 cm plate of the A-W GC were also evaluated. When the particle size was smaller than 44 μm, intraperitoneal injections of 5 mg per g of body weight of BG, KGS, A-W GC, and A-W-A1 were lethal to the mice. Ceramics in fine powder form, which are generally believed to have higher bioactivity, are associated with higher mortality except A-W-A1. On the other hand, when the particle size of the ceramic was increased, the fatal effects of ceramic powders in mice decreased. Plate form of ceramics implanted I.P. had no systemic effects. Intramuscular or SC injections of bioactive ceramic powder with a particle size smaller than 44 μm had almost no systemic effects. Both the particle size of the ceramic powder and the route of administration influenced the reactivity of the bioactive ceramics in the mice. In conclusion, regardless of particle size, neither SC nor IM injection of large doses of highly bioactive ceramics had an adverse effect on the host (mouse).
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  • 86
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    Journal of Biomedical Materials Research 25 (1991), S. 141-156 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: To evaluate an experimental inorganicbone-particle-impregnated bone cement, canine hip prostheses were implanted in dogs using a regular bone cement on one side and the experimental bone cement on the other. In a preliminary feasibility study, bone ingrowth into the resorbed bone-particle spaces was established 3 months after implantation in three dogs. In a more detailed study, twenty-eight (28) dogs were divided in four groups to delineate the effects of time on the phenomena of bony ingrowth. One month after implantation, active bone ingrowth into the bone cement was obvious. By 3 months postimplantation, the ingrowth appeared to have traversed the thickness of the bone-particle-impregnated cement. By the fifth month, most of the interconnected inorganic bone particles were replaced by new bone. At the end of a year, the ingrown bone was mature and negligible new bone activity was present. Biomechanical pushout tests closely corroborated the histologic observations. The maximum shear strength of the cement/bone interface of the experimental side reached 3.6 times that of the control side at 5 months postimplantation. No further improvements were seen at 12 months postimplantation. A viable bone/cement interface may result in a better orthopedic implant fixation system by combining the advantages of both cement for immediate rigidity and biological ingrowth for longterm stability.
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  • 87
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    Journal of Biomedical Materials Research 25 (1991), S. 199-211 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Biomaterials activate the complement system which is important since C3a promotes platelet aggregation and release, and C5a activates neutrophils that may augment coagulation. Tiny air nuclei (microbubbles) are found in the surface roughness of biomaterials on exposure to a liquid, therefore two interfaces exist: (a) a blood/biomaterial, and (b) a blood/air interface. Experiments were carried out that documented that air bubbles activate complement and augment in vitro platelet aggregation in human plasma. The air nuclei were removed from the surface of silicone rubber by a technique termed denucleation to determine if complement activation and platelet aggregation could be reduced. We observed a significant reduction in C3a and C5a in the plasma samples incubated with denucleated silicone rubber as compared to the control samples (p 〈 0.001, ANOVA). The plasma incubated with the denucleated silicone caused reduced platelet aggregation as compared to the plasma incubated with the control silicone when added to a platelet suspension (p 〈 0.001, ANOVA). Surface chemical analysis by x-ray photoelectron spectroscopy (XPS) showed no change in the silicone rubber surface after the denucleation procedure.
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  • 88
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    Journal of Biomedical Materials Research 25 (1991), S. 255-265 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 89
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    Journal of Biomedical Materials Research 25 (1991), S. 165-175 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The studies presented in this paper evaluate the modulatory role of protein preadsorbed polydimethylsiloxane (PDMS) and Biomer on the secretion of fibroblast stimulating growth factors from human monocytes/macrophages. The results of these studies show that Biomer and PDMS selectively activate human monocytes to produce fibroblast “progression-like” and to a lesser extent “competence-like” stimulating growth factors. Polydimethylsiloxane stimulated the monocytes/macrophages to produce more “progression-like” fibro-blast stimulating growth factors than Biomer. The induction of “competencelike” fibroblast stimulating activity from the monocytes was enhanced by preadsorption of PDMS with human derived fibrinogen, fibronectin, IgG, hemoglobin, or albumin. This phenomenon was not observed with protein preadsorbed Biomer. These studies support the hypothesis that protein preadsorbed polymers will selectively modulate monocyte/macrophage activation and induction of growth factors which have the potential to participate in tissue-implant interactions in vivo.
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  • 90
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The adhesion and detachment of platelets were studied on glass coatings of a series of copolymers of hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA). Observations of the interactions of mepacrine labelled washed platelets with these surfaces from a flowing (500 s-1 wall shear rate) suspension in Tyrode's solution containing albumin and red cells were made with epifluorescent video microscopy (EVM). Total platelet adhesion, including platelets which adhere on first contact and platelets which attach temporarily before adhesion, and the number of detaching platelets were minimal for the 0 and 20% EMA copolymers, reached a maximum for the 50% EMA copolymer and showed reduced values for the 80% and 100% EMA copolymers. For the 50, 80, and 100% EMA copolymers, the adhesion values expressed, as a percentage of total contacting platelets, were not different. Albumin adsorption to these copolymers shows a continuous increase from the 0% to the 100% EMA copolymer. It is likely that the peak in platelet adhesion at the 50% EMA composition is related to: low protein adsorption on the 0 and 20% EMA copolymers, too little albumin adsorption to block adhesion on the 50% EMA copolymer, and full-scale blocking on the 80 and 100% EMA copolymers due to greater albumin adsorption.
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  • 91
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    Journal of Biomedical Materials Research 25 (1991), S. 223-242 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The attachment, spreading, spreading rate, focal contact formation, and cytoskeletal organization of human umbilical vein endothelial cells (HUVECs) were investigated on substrates that had been covalently grafted with the cell adhesion peptides Arg-Gly-Asp (RGD) and Tyr-Ile-Gly-Ser-Arg (YIGSR). This approach was used to provide substrates that were adhesive to cells even in the absence of serum proteins and with no prior pretreatment of the surface with proteins of the cell adhesion molecule (CAM) family. This approach was used to dramatically enhance the cell-adhesiveness of substrates that were otherwise cell-nonadhesive and to improve control of cellular interactions with cell-adhesive materials by providing stably bound adhesion ligands. Glycophase glass was examined as a model cell-nonadhesive substrate prior to modification, and polyethylene terephthalate (PET) and polytetrafluoroethylene (PTFE) were examined as representative materials for biomedical applications. The peptides were surface-coupled by their N-terminal amine to surface hydroxyl moieties using tresyl chloride chemistry. Prior to peptide grafting, the PET and PTFE were surface hydroxylated to yield PETOH and PTFE-OH. The PET-OH was less cell-adhesive and the PTFE-OH was much more cell-adhesive than the native polymers. Radioiodination of a C-terminal tyrosine residue was used to quantify the amount of peptide coupled to the surface, and these amounts were 12.1 pmol/cm2 on glycophase glass, 139 fmol/cm2 on PET-OH, and 31 fmol/cm2 on PTFE-OH. Although the glycophase glass did not support adhesion or spreading even in the presence of serum, the RGD- and YIGSR-grafted glycophase glass did support adhesion and spreading, even when the only serum protein that was included was albumin. Although PET and PTFE-OH supported adhesion when incubated in serum-supplemented medium, neither of these materials supported adhesion with only albumin present, indicating that cell adhesion is mediated by adsorbed CAM proteins. When these materials were peptide-grafted, however, extensive adhesion and spreading did occur even when only albumin was present. Since the peptide grafting is quite easily controlled and is temporally stable, while protein adsorption is quite difficult to precisely control and is temporally dynamic, peptide grafting may be advantageous over other approaches employed to improve long-term cell adhesion to biomaterials.
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  • 92
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    Journal of Biomedical Materials Research 25 (1991) 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 93
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    Journal of Biomedical Materials Research 25 (1991) 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 94
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    Journal of Biomedical Materials Research 25 (1991), S. 407-420 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Albumin and fibrinogen were competitively adsorbed onto dimethyldichlorosilane-coated glass (DDS-glass) and platelet activation was examined as a function of the surface fibrinogen concentration. The weight ratio of albumin to fibrinogen in the adsorption solution was varied from 10 to 700. Platelet activation was quantitated by the area and circularity of spread platelets. When the DDS-glass was coated with albumin alone, platelets were only contact adherent and could not spread at all. After competitive adsorption of fibrinogen and albumin, however, platelets were able to spread on the surface. Platelet activation increased linearly as the surface fibrinogen concentration increased up to 0.02 μg/cm2. Platelets were able to activate fully if the surface fibrinogen concentration was 0.02 μg/cm2 or higher, even though the surface was dominated by albumin. It appears that platelets can activate fully as long as only a small fraction (2-15%) of the surface is covered with tightly bound fibrinogen.
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  • 95
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    Journal of Biomedical Materials Research 25 (1991), S. 459-465 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The nature and mechanism of calcium complexation with human serum components in the presence of silicone rubber were assessed in in vitro model experiments. Silicone rubber samples were incubated for 67 h in serum of both physiologic calcium concentrations and induced hypercalcemic levels. Physiologic calcium incubation decreased the intrinsic and nth binding site association constants by factors of 2 and 4, respectively, from initial serum values. Incubation with silicone rubber did not change the association constants. Hypercalcemia incubation lowered the intrinsic and nth binding site association constants by 39 and 61%, respectively. Polymer incubation increased the intrinsic association constant and decreased the number of binding sites by a factor of 2. With initial binding site association constants unperturbed by incubation and Hill coefficients equivalent to 1, complexation was noncooperative and binding sites were considered to be identical and independent. Both Scatchard and Hill plots show nonlinearity for the polymer incubation case giving two distinct linear regions. This is indicative of cooperative binding for incubation with polymer; the Hill coefficient for the physiologic calcium concentration range was 0.97, while the coefficient for the hypercalcemic calcium range was 6.
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  • 96
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    Journal of Biomedical Materials Research 25 (1991), S. 515-523 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We have previously studied a large number of histological specimens of biomaterials and found that regions with and without an intervening fibrous membrane coexisted in many specimens. Therefore, it appears necessary to perform an evaluation of the entire specimen when histologically assessing the affinity of bone for a biomaterial. Accordingly, we performed a quantitative histological evaluation of hydroxyapatite (HAP)- and titanium- oxide(TiO2)-coated Ti-6Al-4V and uncoated Ti-6Al-4V (control) by determining the affinity index. This was defined as the length of bone directly opposed to the implant/the total length of the bone--implant interface X 100%. The test materials were inserted into the distal epiphyseal region of the femurs of adult dogs, and follow-up quantitative histological comparisons were performed from 4 weeks to 96 weeks. The HAP-coated implants had the highest affinity index 4 weeks after insertion, and this superiority was maintained up to 96 weeks. There was a significant difference in affinity index between HAP-coated implants and control implants (P 〈 0.001), while TiO2-coated implants showed no significant difference in comparison to the control.
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  • 97
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    Journal of Biomedical Materials Research 25 (1991), S. 357-365 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An apatite- and wollastonite-containing glass-ceramic (A · W-GC) has been reported to form a tight bond with living bone through an apatite layer formed on its surface. This layer is considered to be formed by dissolution of Ca2+ and HSiO3- ions from the glass-ceramic into the surrounding body fluids. In order to confirm this proposed mechanism for the surface reaction of A · W-GC, three kinds of glass in the systems CaO—SiO2, CaO—SiO2—CaF2, and CaO—SiO2—P2O5 were implanted into the tibiae of rabbits for 3 or 8 weeks. Contact microradiography and SEM-EPMA showed that all three kinds of glass formed a Ca, P-rich layer in combination with a Si-rich layer on their surfaces within 3 weeks and formed a direct bond with bone via these layers. The detaching test, performed 8 weeks after implantation, showed that the loads required to detach the implants from the bone were almost equal for the phosphorus-free and the phosphorus-containing glasses. It was concluded that even P2O5-free CaO · SiO2 glass formed a Ca,P-rich layer on its surface and bonded tightly with living bone. If glasses and glass-ceramics release at least Ca2+ and HSiO3- ions, this would be sufficient for them to form the Ca,P-rich layer on their surfaces in vivo, enabling them to bond directly with bone.
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  • 98
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    Journal of Biomedical Materials Research 25 (1991), S. 589-608 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Single and multi-strand stainless steel and cobalt-nickel alloy wires, with strand diameters from 26 to 46 μm, were fatigue tested using a modified rotating bending test to determine what factors are most important in controlling fatigue life. The relation between cyclic strain and cyclic life was determined for each material by cyclically straining test specimens at various strain ranges and recording the number of cycles to failure. The results show that (a) the fatigue curves of the 316LVM, MP35N, DBS, and Syntacoben wires are very similar and have many of the same fatigue characteristics of specimens of large cross section. (b) Multi-stranded wires have the same average fatigue life as their individual constituent strands but the variance of that life is smaller (c) Deformities in the wire, which are created during the manufacturing, appear to have the effect of shortening the fatigue life of these small section wires. (d) Observation of wire fracture surfaces show a relatively small crack propagation zone and a large fast fracture zone suggesting that most of the fatigue life of these small wires is in the original crack formation, which creates a large stress concentration and quickly leads to wire failure, (e) The size of the wire cross sectional area is of secondary importance compared to the amplitude of the maximum cyclic strain of the individual strands in determining fatigue life of the cable. To maximize the fatigue life of electrodes in vivo, the highest fatigue life for a given bending radius of curvature is desired. This suggests wire strands should be manufactured at the smallest diameter possible (without introducing structural flaws) to maximize service life.
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  • 99
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    Journal of Biomedical Materials Research 25 (1991), S. 637-649 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The activation of cells by interaction with solid surfaces is important in many settings, including the response of tissue to implanted materials. However, few comprehensive studies of both cell migration and activation have been performed so that the connection between these events and immunological activation against foreign material is not well understood. In the present study, synthesis and expression of Ia antigens by peritoneal exudate macrophages after implantation of different carbon fiber composites in the rat peritoneal cavity have been investigated in order to determine whether the type of material implanted affected the composition of Ia-bearing cells of the exudate. The results have confirmed the low level of expression of Ia on resident peritoneal macrophages; while we have found that macrophages, harvested after implantation, express a different amount of Ia related to the different cure cycles of the composite materials used.
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    Journal of Biomedical Materials Research 25 (1991), S. 698-698 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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