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  • Polymer and Materials Science  (112,478)
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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: fiber-optic pH sensor ; pH sensing membrane ; fluorescent probe ; SNAFL ; photo-crosslinking ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A fiber-optic pH sensor was prepared using the self-referencing fluorescent pH probe carboxy seminaphthofluorescein (SNAFL-2). The ratio of the emission from the base form of this dye and the emission near the isoemissive point is insensitive to variations in the excitation intensity and photobleaching. The carboxy SNAFL-2 and a photoaffinity crosslinker, 4-azido-2,3,5,6-tetrafluorobenzoic acid, succinimidyl ester, were attached onto poly(acrylamide-co-vinylamine) to form a hydrophilic functional membrane for the fiber-optic sensor. Photo crosslinking was used to create a crosslinked pH-sensing membrane and covalently bind the membrane onto the surface of the PMMA optical fiber. The fluorescent properties of the membrane-fiber conjugate have been determined. The membrane is stable, and the pH sensor shows a fast response time and excellent resolution in a wide pH range of 3 to 11. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 9-15, 1998.
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: in situ hybridization ; collagen I ; osteoblast ; bioactive materials ; osteoconduction ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Osteoblast activation after implantation of two kinds of surface-active material in bone was investigated chronologically using in situ hybridization with digoxygenin-labeled procollagen α1(I) complementary RNA probe. The bioactive materials used were hydroxyapatite (HA) and apatite- and wollastonite-containing glass-ceramic (A-W GC). A hole was drilled bilaterally in the distal epiphysis of rabbit femurs with subsequent implantation of HA or A-W GC cylinders in a press-fit manner. Specimens were collected at 3, 7, 14, and 28 days after operation and decalcified. Then the undecalcified implant cores were pushed out of the hole without causing damage to the bony side of the interface. In situ hybridization documented no qualitative differences in the expression of procollagen α1(I) RNA between HA and A-W GC. Few osteoblasts at the bone-material interface showed a specific signal at day 3, whereas many osteoblasts were positive around the materials at days 7 and 14, indicative of active new bone formation. The positive osteoblasts seemed to originate from preexisting trabeculae and lined the trabeculae, newly formed bone, and material surface. At day 28, many osteoblasts lining material-surrounding bone were negative, whereas those in remodeling canals were positive, suggesting that the bone was in the remodeling stage after bone formation. These findings were comparable to those with β-tricalcium phosphate in a previous study, thus suggesting osteoconductive bone formation on HA and A-W GC. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 1-8, 1998.
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: immobilized heparin ; albumin gelatin coating ; smooth-muscle cells ; growth inhibition ; vascular prosthesis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Gelatin or a mixture of albumin and gelatin has been proposed for the coating of vascular grafts according to their surface thrombogenicity and biocompatibility, and the possibility of biodegradation. Heparin treatment of hemocompatible surfaces improved the patency of prostheses. In this study, different amounts of heparin were immobilized on these protein gels using a water-soluble carbodiimide [1-ethyl-3-(3-dimethylaminopropyl) carbodiimide]. The results showed a coupling of heparin with gelatin and/or albumin at the surface of the gels, stable for as long as 1 month. From 0.20 to 3.60 μg · cm-2, heparin could be immobilized. The antiproliferative activity of immobilized heparin was controlled toward bovine smooth-muscle cells grown on these gels. Cell growth inhibition was dose dependent, but the percentages of inhibition were lower at day 8 than at day 4 at any heparin concentration used under experimental conditions. Referring to heparin in solution, immobilized heparin displayed an antiproliferative activity that improved the potential interest for coating. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 446-452, 1998.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: bone repair ; biomaterial ; positively charged resin ; physeal injury ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Because exposure to positively charged dextran resin (PCDR) inhibits the growth of cultured rat and human bone cells, we tested the hypothesis that PCDR might inhibit bone repair in vivo. Central physeal defects were created by drilling 3.0-mm holes from the proximal tibial plateau into the metaphysis. The defects in left tibiae were packed with neutral resin (control); those in right tibiae were filled with PCDR. At the end of the 1st, 2nd, 3rd, and 10th postoperative weeks, the outcomes were quantitated by documenting the percent trabecular bone volume within the defect. The PCDR-filled defects showed a significant decrease in trabecular bone formation as early as the 2nd week. By the 10th postoperative week, formation of trabeculae had been reduced by nearly 40%. The inhibition conferred by PCDR suggests that the resin could be used as a suppressive interpositional material. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 458-461, 1998.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: sclera ; collagen ; piezoelectricity ; dehydration ; sample orientation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The piezoelectric coefficients (d31) for a number of bovine and human scleral collagen samples were determined as a function of drying time at room temperature. The measured values of d31 decreased with drying time. There were significant differences in the values of the d-coefficient between the human and bovine eyes as well as in the values obtained from different regions of the eye. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 453-457, 1998.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: fibrin sealant ; connective tissue ; Tissucol ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Fibrin sealants are very useful in different surgical fields. Fixation of free gingival grafts, root coverage procedures, and other techniques increasing connective tissue attachment may be associated with the application of Tissucol® in periodontology. The aim of this study was to evaluate the influence of the fibrin sealant in the extracellular matrix, as well as alterations of the connective tissue matrix during wound-healing processes. In the back dermis of 15 Net male rats, Tissucol® was implanted after intraperitoneal anesthesia. The implant material was placed in subcutaneous pockets (2 cm in length) which were sutured with interproximal sutures (test and control pockets). At 4, 7, 14, 21, and 28 days after surgery, biopsies of the healed and surrounding tissues were taken, frozen in liquid nitrogen, and examined histologically and immunohistochemically with antibodies against collagen types I, III, IV, V, VI, and VII. The findings showed thick and thin collagen type I and III fibers, respectively, with different orientations localized around the implant material. An increased amount of blood vessels and capillaries (their basement membranes containing collagen type IV) was observed during wound healing which may be associated with the implantation of the sealant. Collagen type V fibers were localized from the first days to the 4th postoperative week and, without any inflammatory reaction (according to histologic staining), formed a fibrillar extracellular matrix with high collagenase resistance. Collagen type VI showed a microfibrillar pattern of distribution, and collagen type VII was localized in the dermo-epidermo junction and very deep in the connective tissue in the form of anchoring fibers (only in the test group) during the 4 postoperative weeks of healing. The data showed that Tissucol® is a biocompatible component which cannot produce any extensive inflammatory reaction in the matrix. New blood vessel formation, an epithelial-connective tissue interface with high stability, as well as matrix alterations with high resistance in the proteolytic enzymes (i.e., collagenases) can be induced in the connective tissue after use of a fibrin sealant. All of these characteristics may be of great importance in connective tissue healing in periodontal surgical procedures. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 462-468, 1998.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: poly(urethane)s ; monocyte-derived macrophages ; cholesterol esterase ; biodegradation ; biostability ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Monocytes adherent to implanted biomaterials differentiate into macrophages while synthesizing large amounts of degradative enzymes, including cholesterol esterase (CE), which previously has been shown to degrade poly(urethane)s. Human peripheral blood monocytes were cultured on tissue culture grade polystyrene (PS), and two model poly(urethane)s were synthesized from (1) polycaprolactone (PCL) and (2) polytetramethylene oxide (PTMO), both with 2,4-toluene diisocyanate (TDI) and ethylene diamine (ED). The increase in CE and total protein per cell were measured on days 8 and 28 in culture and normalized to the DNA content per cell. At day 8 there consistently were fewer cells remaining on the PTMO-based polymer than on the PCL-based polymer or the PS (p 〈 0.05). When comparing day 28 to day 8, there was more CE activity and protein per cell on all materials. However, there was a disproportionate synthesis of CE per mg of total protein on PS and TDI/PCL/ED whereas on PTMO there was not. Significantly, there was more protein and CE per cell on PTMO than on PS or TDI/PCL/ED (p 〈 0.05). This in vitro model system of the chronic phase of inflammation has shown that it is possible to culture monocytes for a month and assess the material surface itself as a potent activator of the differentiation into macrophages without secondary stimulation. Since CE has been shown to degrade poly(ether and ester)-based poly(urethane)s, the differential production of this enzyme relative to the total protein on different surfaces may impact on the potential long-term biostability of an implanted material. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 469-477, 1998.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: nanoparticles ; protein adsorption ; 2-D PAGE ; drug targeting ; colloidal drug carriers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Plasma protein adsorption patterns on colloidal drug carriers acquired after iv administration depend on their surface characteristics and are regarded as key factors for their in vivo organ distribution. Polymeric latex particles with strongly differing surface properties were synthesized as models for colloidal drug carriers for tissue-specific drug targeting via the intravenous route. Physicochemical characterization was performed for size, surface charge density, zeta potential, and surface hydrophobicity. The interactions with human plasma proteins were studied by way of two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). Considerable differences in protein adsorption on the latex particles were detected with regard to the total amount of surface-bound protein on the various particle types as well as specific proteins adsorbed, for example, fibrinogen, albumin, and a recently identified plasma glycoprotein. Possible correlations between protein adsorption patterns and the physicochemical characteristics and topography of the polymeric surfaces are shown and discussed. Knowledge about protein-nanoparticle interactions can be utilized for the rational design of colloidal drug carriers and also may be useful for optimizing implants and medical devices. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 478-485, 1998.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: poly(vinyl alcohol) ; chitosan ; hydrogel ; cultured fibroblast cell ; cell attachment and growth ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Hydrogels were prepared from poly(vinyl alcohol) and chitosan in various blend ratios. The water contents of the hydrogels were in the range of 65 to 75 wt %. The attachment and growth of fibroblast cells (L-929) on the hydrogels were studied with a cell culture method. On the hydrogels with more than 15 wt % chitosan content, the attached cells were able not only to remain viable but also to proliferate. The relative cell attachment after incubation for 30 h increased with increasing chitosan content in the hydrogels. Cell attachment and growth on the hydrogel with 40 wt % chitosan content exceeded those on collagen, a widely-used mammalian cell culture substrate. The morphology of the cells attached onto the hydrogels with a lower chitosan content was spherical, but in hydrogels with more than 15 wt % chitosan content, the number of spindle-shaped cells increased with increasing chitosan content. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 486-490, 1998.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: biomaterial ; mechanism of calcification ; diffusion chamber ; calcium-containing deposits ; protein sorption ; SEM-XRMA ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In experiments in vivo using diffusion chambers, the morphology and composition of calcium-containing deposits on natural and artificial biomaterials that had no direct contact with cells were studied using scanning electron microscopy with energy dispersion X-ray microanalysis. It was revealed that the formation of a protein layer containing protein-calcium complexes is the key event in biomaterial calcification. A mechanism of formation of a calcium-containing protein matrix that creates the conditions for supersaturation of the crystal-forming medium over critical value has been proposed. The formation of nuclei of insoluble calcium phosphate starts predominantly deep in an adsorbed protein layer enriched by calcium ions. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 491-497, 1998.
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  • 11
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: intracellular cAMP ; biomaterials cell adhesion ; signaling by the biomaterials ; Cuprophan (CU) ; AN69 ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The processing of signals produced when cells contact biomaterials was examined. Of the several possible pathways, this study focuses on the amount of cAMP that accumulated in NIH 3T3 cells during the first 45 min after the cells contacted the bioincompatible membrane Cuprophan (CU) and the biocompatible membrane AN69. The cells that adhered to CU contained more cAMP than those that attached to AN69. This might be because the cells did not spread but remained rounded up under scanning electron microscopy. There was no increase in cAMP in the cells that did not adhere to CU. The cAMP-modulating agents, forskolin and isoproterenol, were used to assess the cAMP-generating capacity of adenylylcyclase in cells adhering to CU and AN69. This capacity was not affected by a high concentration (100 μM) of forskolin. Isoproterenol had no effect on the cAMP content of the cells, demonstrating that β adrenergic receptors are not implicated in the activation of cAMP production by membranes. The bioincompatibility of CU seems to be responsible for the greater amount of cAMP in adherent cells, and this parameter could provide an index for assessing biocompatibility. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 506-510, 1998.
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  • 12
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: resin composite ; silane treatment ; mechanical properties ; water sorption ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A series of microfilled resin composites were formulated by incrementally mixing either agglomerated 20 nm or unagglomerated 50 nm silica microfillers into monomers composed of diphenyloxymethacrylate and TEGDMA. The microfiller particles were prepared with and without a γ-methacryloxypropyl-trimethoxy silane coupling agent. Following polymerization, five material properties were tested: uniaxial tensile strength, Young's modulus in slow compression, Knoop hardness, water sorption, and toothbrush abrasion resistance. Results from these tests indicated that microfiller content clearly was the most influential parameter affecting material property performance. Composites containing 20 nm particles demonstrated greater water sorption, higher Knoop hardness, and better resistance to toothbrush wear. Surprisingly, the application of silane to microfiller surfaces did not greatly improve composite performance for most of the material properties tested in this study. However, water sorption behavior over a 3-year period was observed to be more stable for materials possessing silane-treated particles. Future evaluation of coupling agents should include long-term water storage prior to conducting mechanical tests. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40,12-23, 1998.
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  • 13
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: surface characteristics ; titanium implants ; osseointegration ; bone response ; loaded implants ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Many dental clinical implant studies have focused on the success of endosseous implants with a variety of surface characteristics. Most of the surface alterations have been aimed at achieving greater bone-to-implant contact as determined histometrically at the light microscopic level. A previous investigation in non-oral bone under short-term healing periods (3 and 6 weeks) indicated that a sandblasted and acid-etched titanium (SLA) implant had a greater bone-to-implant contact than did a comparably-shaped implant with a titanium plasma-sprayed (TPS) surface. In this canine mandible study, nonsubmerged implants with a SLA surface were compared to TPS-coated implants under loaded and nonloaded conditions for up to 15 months. Six foxhound dogs had 69 implants placed in an alternating pattern with six implants placed bilaterally in each dog. Gold crowns that mimicked the natural occlusion were fabricated for four dogs. Histometric analysis of bone contact with the implants was made for two dogs after 3 months of healing (unloaded group), 6 months of healing (3 months loaded), and after 15 months of healing (12 months loaded). The SLA implants had a significantly higher (p 〈 0.001) percentage of bone-to-implant contact than did the TPS implants after 3 months of healing (72.33 ± 7.16 versus 52.15 ± 9.19; mean ± SD). After 3 months of loading (6 months of healing) no significant difference was found between the SLA and TPS surfaced implants (68.21 ± 10.44 and 78.18 ± 6.81, respectively). After 12 months of loading (15 months of healing) the SLA implants had a significantly greater percentage (p 〈 0.001) of bone-to-implant contact than did the TPS implants (71.68 ± 6.64 and 58.88 ± 4.62, respectively). No qualitative differences in bone tissue were observed between the two groups of implants nor was there any difference between the implants at the clinical level. These results are consistent with earlier studies on SLA implants and suggest that this surface promotes greater osseous contact at earlier time points compared to TPS-coated implants. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 1-11, 1998.
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  • 14
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: protein adsorption ; ceramic ; albumin ; IgG ; fibrinogen ; fibronectin ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Ceramics seldom have been used as blood-contacting materials. However, alumina ceramic (Al2O3) and polyethylene are incorporated into the pivot bearings of the Gyro centrifugal blood pump. This material combination was chosen based on the high durability of the materials. Due to the stagnant flow that often occurs in a continuous flow condition inside a centrifugal pump, pivot bearing system is extremely critical. To evaluate the thombogenicity of pivot bearings in the Gyro pump, this study sought to investigate protein adsorption, particularly albumin, IgG, fibrinogen, and fibronectin onto ceramic surfaces. Al2O3 and silicon carbide ceramic (SiC) were compared with polyethylene (PE) and polyvinylchloride (PVC). Bicinchoninic acid (BCA) protein assay revealed that the amount of adsorbed proteins onto Al2O3 and SiC was significantly less than that on PVC. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated that numerous proteins adsorbed onto PVC compared to PE, Al2O3, and SiC. Identification of adsorbed proteins by Western immunoblotting revealed that the adsorption of albumin was similar on all four materials tested. Western immunoblotting also indicated lesser amounts of IgG, fibrinogen, and fibronectin on Al2O3 and SiC than on PE and PVC. In conclusion, ceramics (Al2O3 and SiC) are expected to be thromboresistant from the viewpoint of protein adsorption. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 24-30, 1998.
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  • 15
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: urothelial cell culture ; biocompatibility evaluation ; materials testing ; urinary catheters ; barium ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: For several years, studies performed to estimate in vitro biocompatibility of urinary catheters have been carried out using permanent cell lines. But for a rational design of the testing procedure, the cell culture model should relate to the material application. This work presents the results of a probe study designed to obtain an in vitro model of normal human urothelial cells (HUC) and to test the relevance of this system in cytocompatibility experiments of urinary catheters currently used. A comparison is made with continuous cell lines, the use of which is recommended by normalization bodies. We exposed monolayers of HUC (well characterized for their proliferation, qualitative evaluation, and quantitative measurement of cytokeratins) and two continuous human cell lines to liquid extracts (either pure or diluted in the culture medium) of nine available catheters, including positive (latex) and negative controls, for a 24 h incubation. Then colorimetric assays (Neutral Red and MTT) were performed. The extracts of two polyurethanes provoked a significant toxic effect on HUC only, suggesting differences in sensitivity between the models used. This effect could be due to the presence of a great amount of barium (used as a radioopacifier) in extracts, as highlighted by results of absorption emission spectroscopy. A culture model of HUC may be of relevance for the screening of materials intended for urological practice. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 31-39, 1998.
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  • 16
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: nickel ; biomaterial ; mice ; microelectrodes ; histology ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The toxic effects caused by nickel (Ni) per si were explored by performing in vivo studies on mice following subcutaneous administration of a metallic solution of nickel at 1, 2, 3, and 4 weeks to evaluate the side effects of this metal ion when released from stainless steel implants. Other groups were similarly injected with HBSS and used as controls. Accumulation of Ni ions on liver, spleen, and kidney was assessed by an electrochemical method, adsorptive stripping voltammetry (AdSV) using microelectrodes, and atomic absorption spectrometry (AAS). Alterations of those organs induced by Ni ions were studied, showing that several histological changes had been induced. Chemical analysis and histological features indicate that Ni is partially accumulated in the study organs. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 40-47, 1998.
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  • 17
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    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: polysaccharides ; DTAF labeling ; radiolabeling ; smooth-muscle cells ; confocal analysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Glycosaminoglycans (GAGs) such as heparan sulfates are complex carbohydrate polymers. These structural components of the extracellular matrix are essential for the adhesion, migration, and regulation of cellular growth. To understand the physiological role of GAGs and GAG analogues, a practical approach consists of labeling and detecting them in cell extracts, or analyzing binding domains and their distributions into the cells. We propose a convenient and reliable method for preparing and labeling amino-enriched polysaccharides with the fluorescent derivative 5-[(4,6-dichlorotriazine-2-yl)amino]-fluorescein (DTAF). Radioiodination is then performed on the DTAF moiety. This method was applied to polysaccharides known to inhibit vascular smooth-muscle cell (SMC) proliferation such as functionalized dextrans derived from poly(α1-6 glucose) and fucan, poly(L-fucose 4-sulfate) extracted from brown seaweed. Using autoradiography and confocal microscopy, we observed the fixation and internalization of labeled antiproliferative products in SMCs from rat aorta. These probes can be useful for the understanding of polysaccharide-cell interactions. In addition, the method presented here can be applied to various synthetic or natural biomedical materials. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 275-281, 1998.
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  • 18
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    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: surface topography ; actin ; vinculin ; fibronectin ; vitronectin ; grooves ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The microfilaments and vinculin-containing attachment complexes of rat dermal fibroblasts (RDF) incubated on microtextured surfaces were investigated with confocal laser scanning microscopy (CLSM) and digital image analysis (DIA). In addition, depositions of bovine and endogenous fibronectin and vitronectin were studied. Smooth and microtextured silicone substrata were produced that possessed parallel surface grooves with a groove and ridge width of 2.0, 5.0, and 10.0 μm. The groove depth was approximately 0.5 μm. CLSM and DIA make it possible to visualize and analyze intracellular and extracellular proteins and the underlying surface simultaneously. It was observed that the microfilaments and vinculin aggregates of the RDFs on the 2.0 μm grooved substrata were oriented along the surface grooves after 1, 3, 5, and 7 days of incubation while these proteins were significantly less oriented on the 5.0 and 10.0 μm grooved surfaces. Vinculin was located mainly on the surface ridges on all textured surfaces. In contrast, bovine and endogenous fibronectin and vitronectin were oriented along the surface grooves on all textured surfaces. These proteins did not seem to be hindered by the surface grooves since many groove-spanning filaments were found on all the microgrooved surfaces. In conclusion, it can be said that microtextured surfaces influence the orientation of intracellular and extracellular proteins. Although results corroborate three earlier published hypotheses, they do not justify a specific choice of any one of these hypotheses. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 291-300, 1998.
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  • 19
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    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: biocompatibility ; biomaterials ; human bone marrow cell culture ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A cell culture system for biocompatibility testing of hip implant materials is described. Human bone marrow cells have been chosen because these cells are in direct contact with the biomaterial after implantation in situ. The sensitivity of this method is evaluated for materials which are already being used as implants in humans and animal, e.g., hydroxyapatite (HA) ceramic, pure titanium, and ultra-high-molecular-weight polyethylene (UHMWPE). As indicative parameters of biocompatibility primary cell adherence, cell number, cell proliferation, production of extracellular matrix, cell vitality, and cell differentiation are described. After 2 weeks in culture, obvious differences between the biomaterials with respect to the indicative parameters could be observed. Cell numbers were greatest on the HA specimens. In the case of titanium alloys, we observed a decreased number of cells. The production of extracellular matrix was high for the HA ceramics but reduced for titanium specimens. The polymers allowed only a few adherent cells and showed no signs of extracellular matrix production. The results can be correlated astonishingly well to animal experiments and clinical experiences. Therefore, we suggest that this cell culture system seems to be a useful tool for biocompatibility testing of bone implantation materials. It also helps reduce animal experiments. With the help of flow cytophotometry, we analyzed the influence of biomaterials on large numbers of cells with respect to differentiation. There were similar populations of T cells and monocytes on all specimens tested. Extended B-cell and granulocyte populations, however, were observed with titanium and UHMWPE. Most osteocalcin-containing cells adhered to the HA ceramics. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 301-306, 1998.
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  • 20
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    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: dental implants ; bone formation ; cell differentiation ; osteointegration ; dental material ; bone substitutes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A proposed in vitro system is described where chick osteoblasts are cultured on the flat surfaces of dense, nonporous HA disks to facilitate the study of bone formation at the cell-HA interface. During early bone formation cell-coated HA disks were retrieved, fixed with buffered 2% glutaraldehyde, and embedded in epon/araldite. The underlying HA disks were demineralized in diluted acid, and the intact cell-HA interfaces were re-embedded and thin sectioned for routine transmission electron microscopy. Morphologic studies indicated that osteoblasts proliferated and formed nodules of cells on the surfaces of HA disks. With increasing time in culture, they deposited orthogonally packed collagen fibrils between the cell layers that were enveloped by electron-dense mineralized globules. Eventually, small spicules of mineralized HA formed along collagen fibrils. An electron-dense layer about 50 nm thick was observed on the surface of the HA disks. Biochemical studies indicated that cell proliferation, as judged by 3H-thymidine uptake, increased rapidly during the first 3 days, reached a maximum around 6 days, and then declined by 12 days in culture. AP activity and collagen synthesis, as determined by 3H-hydroxyproline formation, increased as cellular proliferation declined. Mineralization, as judged by 45Ca uptake and spicule formation, occurred, as expected, following the increase in AP activity and deposition of densely packed collagen fibrils. Thus, all morphological and biochemical parameters studied indicate that the proposed in vitro system is reproducible and can facilitate the study of the osteointegration of HA-coated implants. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 282-290, 1998.
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  • 21
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    ISSN: 0021-9304
    Keywords: pyrolytic carbon ; mammary tissue expanders ; biocompatibility ; image analysis ; cellular proliferation ; MIB-1 ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The authors investigated tissue reaction around implanted silicone expanders, focusing on clinical morphological and morphometrical aspects. For use in breast reconstruction in post mastectomy patients, the surface of a medical-grade silicone elastomer was modified, without changing its bulk properties, by the addition of a pyrolytic carbon film. The presence of lipophagy, the number of foreign-body giant cells of histiocytic origin, and the number of MIB-1 positive nuclei (an index of proliferation for the reactive stromal population) were all seen to be influenced by the pyrolytic carbon coating. Indeed, all these parameters were lower in the membrane formed around Carbofilm™-coated expanders, thus demonstrating the effective protective properties of pyrolytic carbon coating. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 307-313, 1998.
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  • 22
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    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: polyethylene oxide (PEO) ; sulfonated PEO ; surface modification ; segmented polyurethane ; platelet adhesion ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Polyethylene oxide (PEO) surfaces were prepared by the addition of PEO- and sulfonated PEO-containing amphiphilic block copolymers as surface-modifying additives in a segmented polyurethane (PU). PEO-PPO-PEO triblock copolymers (Pluronics) with different PEO chain lengths (from 2 to 80) were used as additives. The prepared film surfaces were characterized by the measurement of dynamic water contact angles and electron spectroscopy for chemical analysis. It was observed that the PU films containing 10 wt % of PEO additives were surface-saturated with the additives regardless of their PEO chain length, but the PEO chains were more projected from the film surfaces containing the additives with longer PEO chains. The water absorption of the films increased largely with the increasing PEO chain length of the additives. The addition of PEO additives produced film surfaces that were in a gel-like state. The films demonstrated some extraction of the PEO additives. However, the additives with higher molecular weights were entrapped more stably into the PU matrix. The mechanical properties (tensile strength and elongation) of the films were changed by the addition of PEO additives, but the differences were not significant compared to the control PU. The platelet adhesion on the film surfaces decreased with increasing PEO chain length of the additives. The film surface containing additives with long PEO chains (chain length of 80) was particularly effective in preventing platelet adhesion. The effect of negatively charged sulfonate groups on the prevention of platelet adhesion appeared only on the film surfaces containing additives with short PEO chains. For longer PEO chains, the chain mobility effect was more dominant than the negative charge effect on the prevention of platelet adhesion. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 314-323, 1998.
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  • 23
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    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: adhesion mechanism ; dentin primer ; N-methacryloyl glycine ; dentinal collagen ; prolylprolylglycyl oligomer ; 13C-NMR ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The origin of the pH-dependent bond strength of the resin to etched dentin treated with N-methacryloyl glycine (NMGly) primer was studied by 13C-nuclear magnetic resonance (NMR) including spin-lattice relaxation time, T1, observation. When the dentinal collagen was suspended in the NMGly solution at pH = 1.6, the T1 values of all the carbons attributed to the NMGly species were significantly decreased. This indicated the presence of an interaction between the NMGly and the dentinal collagen. To obtain detailed information of this interaction, the 13C-NMR spectra of the NMGly were measured in the presence of the model compound for the collagen, (Pro-Pro-Gly)5 at pH = 1.7. The 13C-NMR peaks of the carbonyl carbons of the amide and carboxylic acid in the NMGly species shifted to a higher field and the T1 values decreased. Furthermore, when the molar ratio of (Pro-Pro-Gly)5 to NMGly was decreased from 1:1 to 1:3, the T1 values of the carbonyl carbon attributed to the carboxylic acid in the C-terminal Gly residue of the oligopeptide decreased dramatically. It can be construed that this indicated the formation of a hydrogen bond between the amide, -NH and the carboxylic acid of the NMGly species and the carboxylic acid of the C-terminal Gly residue of the oligopeptide. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 458-463, 1998.
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  • 24
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    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: calcium phosphate coatings ; magnetron sputtering ; osteoblast ; in vitro ; bone ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In previous studies we developed a RF magnetron sputter technique for the production of thin Ca-P coatings. With this technique coatings can be produced that vary in Ca/P ratio as well as in structural appearance. The aim of this investigation was to obtain more understanding of the biological behavior of these coatings by way of in vitro experiments. The effect of noncoated titanium (Ti) and three different Ca-P-sputtered surfaces on the proliferation and differentiation (morphology and matrix production) of osteoblast-like cells was studied. Proliferation was determined using counting procedures; morphology was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Fluorescent markers and energy-dispersive X-ray microanalysis (EDX) were used to obtain quantitative and compositional information about the resultant calcified extracellular matrix (ECM). Results demonstrated that proliferation of the osteoblast-like cells was significantly (p 〈 0.05) higher on noncoated than on Ca-P-coated samples. On the other hand, more mineralized ECM was formed on the coated surfaces. In addition, TEM confirmed that the cells on the coated substrates were surrounded by ECM with collagen fibers embedded in crystallized, needle-shaped structures. On the basis of these findings, we concluded that: (1) the investigated Ca-P sputter coatings possess the capacity to activate the differentiation and expression of osteogenic cells, and (2) bone formation proceeds faster on Ca-P surfaces than on Ti substrates. Further, this bone-inductive effect appeared to be dependent on the Ca-P ratio of the deposited coatings. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 464-474, 1998.
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  • 25
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    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: protein adsorption ; grafted PEO ; reflectivity ; star polymers ; end-functional polymers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Four different poly(ethylene oxide) [PEO] molecules were compared as grafted polymer layers for biomaterials' substrates: two linear polymers and two star polymers. Conditions maximizing surface coverage for each molecule were employed with the aim of inhibiting protein adsorption and increasing the density of end groups. Neutron reflectivities of the grafted layers immersed in deuterium oxide (heavy water) were measured and used to calculate volume fraction profiles of the polymer as a function of distance from the surface. These density profiles were combined with protein adsorption data on the grafted layers to compare with recent theoretical and experimental studies of protein resistance by PEO at surfaces. We found that the grafting density is maximized by coupling the linear PEO from a K2SO4 salt buffer, which is a poor solvent for PEO. However, the grafting density of star PEO was maximized when no K2SO4 was used and the stars were dissolved near the overlap concentration. Concentration profiles obtained from the reflectivity data show that the hydrated polymers swell to ∼ 10 times the dried layer thickness and exhibit a low density (maximum volume fractions 〈 0.4 PEO) throughout the layer. The PEO surfaces obtained with both the star and linear polymers resisted adsorption of cytochrome-c and albumin except for a small amount of cytochrome-c adsorption on the short, many-armed star polymer surface. A hypothesis of adsorption on the star polymer layer is presented and criteria for controlling receptor-mediated cell-substrate interactions by ligand-modified chain ends are discussed. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 498-509, 1998.
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  • 26
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    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: PEO chemistry ; cell adhesion ; model surface ; RGD peptide ; surface modification ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The ability to study and regulate cell behavior at a biomaterial interface requires strict control over material surface chemistry. Perhaps the greatest challenge to researchers working in this area is preventing the fouling of a given surface due to uncontrolled protein adsorption. This work describes a method for coupling peptides to hydrophobic materials for the purpose of simultaneously preventing nonspecific protein adsorption and controlling cell adhesion. A hexapeptide containing the ubiquitous RGD cell-adhesion motif was coupled to polystyrene (PS) via a polyethylene oxide (PEO) tether in the form of a modified PEO/PPO/PEO triblock copolymer. Triblocks were adsorbed onto PS at a density of 3.3 ± (5.14 × 10-4) mg/m2 (1.4 × 105 ± 2.12 × 101 molecules/μm2), which was determined by isotope 125I labeling. The peptide, GRGDSY, was activated at the N terminus with N-Succinimidyl 3-(2-pyridyldithio) propionate and coupled to immobilized triblocks where the terminal hydroxyls had been converted to sulfhydryl groups. Surface peptide density was measured by amino acid analysis and found to be 1.4 × 104 ± 0.47 × 104 molecules/μm2. PS modified with PEO/PPO/PEO copolymers alone was found to be inert to cell adhesion both in the presence of serum proteins and when exposed to activated RGD peptide. In contrast, PS conjugated with RGD via end-group-activated PEO/PPO/PEO copolymers supported cell adhesion and spreading. The surface coupling scheme reported here should prove valuable for studying cell-ligand interactions under simplified and highly controlled conditions. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 511-519, 1998.
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  • 27
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    ISSN: 0021-9304
    Keywords: tissue engineering ; synthetic extracellular matrix ; polyglycolic acid ; poly-L-lactic acid ; smooth muscle ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Nonwoven meshes of polyglycolic acid (PGA) fibers are attractive synthetic extracellular matrices (ECMs) for tissue engineering and have been used to engineer many types of tissues. However, these synthetic ECMs lack structural stability and often cannot maintain their original structure during tissue development. This makes it difficult to design an engineered tissue with a predefined configuration and dimensions. In this study, we investigated the ability of PGA fiber-based matrices bonded at their fiber crosspoints with a secondary polymer, poly-L-lactic acid (PLLA), to resist cellular contractile forces and maintain their predefined structure during the process of smooth muscle (SM) tissue development in vitro. Physically bonded PGA matrices exhibited a 10- to 35-fold increase in the compressive modulus over unbonded PGA matrices, depending on the mass of PLLA utilized to bond the PGA matrices. In addition, the bonded PGA matrices degraded much more slowly than the unbonded matrices. The PLLA bonding of PGA matrices had no effect on the ability of cells to adhere to the matrices. After 7 weeks in culture, the bonded matrices maintained 101 ± 4% of their initial volume and an approximate original shape while the unbonded matrices contracted to 5 ± 1% of their initial volume with an extreme change in their shape. At this time the bonded PGA matrices had a high cellularity, with smooth muscle cells (SMCs) and ECM proteins produced by these cells (e.g., elastin) filling the pores between PGA fibers. This study demonstrated that physically bonded PGA fiber-based matrices allow the maintenance of the configuration and dimensions of the original matrices and the development of a new tissue in a predefined three-dimensional structure. This approach may be useful for engineering a variety of tissues of various structures and shapes, and our study demonstrates the importance of matching both the initial mechanical properties and the degradation rate of a matrix to the specific tissue one is engineering. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 322-332, 1998.
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  • 28
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    ISSN: 0021-9304
    Keywords: implant ; titanium ; osteoblasts ; prostaglandin ; indomethacin ; surface roughness ; 1α,25-(OH)2D3 ; differentiation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Surface roughness affects proliferation, differentiation (alkaline phosphatase and osteocalcin), local factor production [transforming growth factor (TGFβ) and prostaglandin E2 (PGE2)], and response to 1,25-(OH)2D3 (1,25) of MG63 osteoblast-like cells. In this study, we examined whether the effect of surface roughness on MG63 cells is mediated by prostaglandins produced by the cells. Unalloyed titanium (Ti) disks were pretreated with HF/HNO3 (PT) and then machined and acid-etched (MA). Disks were also coarse grit-sandblasted (SB), coarse grit-sandblasted and acid-etched (CA), or plasma-sprayed with Ti particles (PS). The surfaces, from smoothest to roughest, were PT, MA, CA, SB, and PS. MG63 cells were cultured to confluence on the Ti disks in the presence or absence of 10-7M indomethacin (Indo), a specific inhibitor of cyclooxygenase activity, resulting in decreased prostaglandin production. When the cells reached confluence, cell number, cell layer alkaline phosphatase specific activity (ALPase), and osteocalcin (OC) and latent TGFβ (LTGFβ) production were determined. In addition, confluent cultures which had been grown in the absence of Indo were exposed to 10-7M 1,25, 10-7M Indo, or a combination of the two for 24 h. On the rougher surfaces, cell number was decreased and ALPase, OC, and LTGFβ were increased. When indomethacin was present throughout the culture period, the effect of surface roughness on cell number, OC, and LTGFβ was abolished. ALPase was reduced, but surface roughness-dependent effects were still observed. Addition of indomethacin to confluent cultures for 24 h had no effect on any of the parameters examined, with one exception: Cells cultured on MA surfaces exhibited a more differentiated phenotype. 1,25 increased all parameters examined on SB, CA, and PS surfaces. When indomethacin was added with 1,25, the 1,25-dependent effects on cell number and OC and LTGFβ production were abolished; however, ALPase was unaffected. This indicates that bone cell response to systemic hormones may be modified by implant surface roughness. This effect may be mediated, at least in part, by prostaglandins produced by the same cells. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 489-496, 1998.
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  • 29
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 30
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 31
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    ISSN: 0021-9304
    Keywords: titania coating ; sol-gel ; apatite-forming ability ; simulated body fluid ; calcium phosphate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Titanium and its alloys are used widely in the manufacture of orthopedic and dental implants. Sol-gel-prepared titania is able to stimulate bone-like apatite formation in in vitro and in vivo cultures. These materials can be used, for example, as coatings on dental and orthopedic implants. However, the processes that lead to apatite formation are not fully understood. In this study different kinds of titania coatings on commercially pure titanium (c.p. Ti) were tested for apatite-forming ability. The rate of apatite formation is considered to be descriptive of a material's bioactive (bone-bonding) potential. Apatite-forming tests were done in simulated body fluid (SBF). Apatite-forming ability was highest with the addition of valeric acid to sol (600°C) or with sintering sol-gel coatings at 450°-550°C. At that temperature range calcium phosphate forms on the coatings in 1 week. Calcium phosphate forming is observed in 1 day on standard coatings sintered at 500°C. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 504-510, 1998.
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  • 32
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    ISSN: 0021-9304
    Keywords: bioactive glass fiber ; bone bonding ; bioactive composite ; push-out test ; in vivo ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Bioactive glass fibers were investigated for use as a fixation vehicle between a low modulus, polymeric composite and bone tissue. In an initial pilot study, bioactive glass fiber/polysulfone composites and all-polysulfone control rods were implanted into the rabbit tibia; the study was subsequently expanded with implantation into the rabbit femur. Bone tissue exhibited direct contact with the glass fibers and adjacent polymer matrix and displayed a mechanical bond between the composite and bone tissue after six weeks implantation. Interfacial bond strengths after six weeks implantation averaged 12.4 MPa, significantly higher than those of the all-polymer controls. Failure sites for the composite at six weeks generally occurred in the bone tissue or composite, whereas the failure site for the polymer implants occurred exclusively at the implant/tissue interface. The bioactive glass fiber/polysulfone composite achieved fixation to bone tissue through a triple mechanism: a bond to the bioactive glass fiber, mechanical interlocking between the tissue and glass fibers, and close apposition and possible chemical bond between the portions of the polymer and bone tissue. This last mechanism resulted from an overspill of bioactivity reactions from the fibers onto the surface of the surrounding polymer which we call the “halo” effect. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 161-170, 1998.
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  • 33
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    ISSN: 0021-9304
    Keywords: polypyrrole ; polyester ; conductivity ; in vitro ; cell culture ; cell activation ; interleukin expression ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Electrically conducting polypyrrole-treated films have recently been shown to influence the morphology and function of mammalian cells in vitro. This type of polymer represents a possible alternative biomaterial for use in vascular implantation. The present study compared the in vitro biocompatibility of five different polyester woven fabrics having increasing levels of electrical conductivity ranging from 4.5 × 104 to 123 Ω/square with that of low density polyethylene and polydimethylsiloxane primary reference materials. Biocompatibility was measured in terms of four different types of in vitro cellular response, including (a) an indirect and (b) a direct control organotypic culture assay using endothelial cells, (c) a polymorphonuclear (PMN) cell activation study using flow-cytometric measurements of CD11/CD18 integrin molecule expression, and (d) a semiquantification of interleukin (IL)-6 mRNA expression on monocytes/macrophages using reverse-transcriptase polymerase chain reaction. The organotypic culture study revealed that the fabrics with high levels of conductivity exhibited lower cell migration, proliferation, and viability. The PMN activation study of blood from 10 healthy adult donors demonstrated that the two most conductive fabrics were able to identify the more reactive donors. The levels of IL-6 mRNA expression by monocytes/macrophages decreased as the conductivity level of the fabrics increased. The results of the present study therefore indicate that high levels of conductivity (〈200 Ω/square) on polyester fabrics are detrimental to the growth, migration, and viability of endothelial cells; induce elevated PMN activation; and affect the intracellular metabolism of monocytes. They also point to a specific range of conductivity (103 〈 104 Ω/square) which is associated with an optimum in vitro cellular response. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 519-526, 1998.
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  • 34
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    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: calcium phosphate bone cements ; compressive strength ; microstructure ; bone apatite ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The hardening properties of calcium phosphate cements in the CaHPO4-α-Ca3(PO4)2 (DCP-α-TCP) system have been investigated with interest focused on the compressive strength and microstructure development. Previous studies have shown that the addition of CaCO3 (CC) leads to a modification of the calcium-deficient apatite structure of the reaction product, which results in a material more similar to the apatite in bone mineral. The addition of 10% w/w of CC to the initial DCP-α-TCP powder mixture resulted, with time, in a retardation of the development of compressive strength. However, the optimum compressive strength reached values up to 40% higher than CC-free samples. This retarding effect also has been monitored as a function of the calcium to phosphorus (Ca/P) ratio of the DCP and α-TCP mixture, showing the importance to the final cement properties of the relative quantities of the reactants in the mixture. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 560-567, 1998.
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  • 35
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    ISSN: 0021-9304
    Keywords: photopultrusion ; composites ; fiber-reinforced polymers ; photopolymerization ; methacrylates ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: To develop a dual-curing monomer system for the photopultrusion of reformable (soft) composites, a microhardness assay showed that in a blend with 2,2-Bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl] propane (Bis-GMA), the substitution of methyl methacrylate (MMA) for triethylene glycol dimethacrylate (TEGDMA) delayed the onset of gelation during photopolymerization. Adding lauroyl peroxide permitted the completion of polymerization thermally. This system was used to form silicate-glass-fiber-reinforced composites, with varying degrees of conversion, by photopultruding over a range of pulling speeds. Sol-gel extractions demonstrated both fully soluble and insoluble matrices. For the soluble material, gel permeation chromatography elucidated a trimodal distribution of molecular weights that corresponded to MMA, Bis-GMA, and polymeric molecules with molecular weights in the tens of thousands. Composites with matrix solubilities above about 10% wt could be swaged after photopultrusion to change the cross section from circular to rectangular before thermal processing. The effect on the final elastic modulus was small (∼44GPa, as measured in flexure for 57% vol-reinforced composites); but the final flexure strength was reduced by approximately 25% to a constant of about 1.2 GPa. Morphological characteristics that were seen in the circular-sectioned precursors were observed in the swaged rectangular products as well, including flaws when swaging was conducted at matrix solubilities above about 75%. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 549-559, 1998.
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  • 36
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    ISSN: 0021-9304
    Keywords: ureteral stents ; film depositions ; bacterial biofilms ; XPS ; SEM ; encrustation ; prophylactic antibiotics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Ureteral stents are commonly implanted to assist the postsurgery flow of urine from the kidney to the bladder. We hypothesized that different surface compositions of stent material could result in different conditioning film depositions and potentially altered receptivity to bacterial biofilms. Using XPS, three types of ureteral stents recovered from 64 patients were found to have adsorbed conditioning films that altered the surface composition of the devices. Elements associated with encrustation (calcium, magnesium and phosphorus) were found on 69% of the silicone latex stents, 44% of the low surface energy (LSe) devices, and 38% of the carbon-rich stents. No statistical difference was found in relation to patient gender, stent type, duration of implantation, and encrustation deposition. The composition of the film suggested that the nature of the underlying material did not significantly alter the elements that adsorbed. Thus, devices may take on a similar surface coat within days, and perhaps hours, of exposure to the host. With respect to dense encrustations, fewer appeared on the LSe devices. SEM confirmed the presence and nature of the film crystals and showed bacterial biofilms adherent to devices and encrustations in three patients who had received prophylactic trimethoprim compared to one on ciprofloxacin. In conclusion, although encrustation deposition and biofilm formation on ureteral stents is not unique to Cook devices, the human model and surface science test systems described here are invaluable to evaluate biomaterials used in patients. Unless biomaterials undergo rigorous analysis in vivo, including true assessment of the outcome of prophylactic antibiotic usage, clinicians will be unable to accurately select the best device and management strategy for a given patient. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 321-330, 1998
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  • 37
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    ISSN: 0021-9304
    Keywords: prostheses-bone interfaces ; histomorphology ; mechanical interlocking ; bone matrix-materials interactions ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In this overview, which is based on selected books and reviews, the microscopic appearances of prosthesis-bone interfaces resulting from clinically relevant implantation techniques are highlighted. The following techniques are distinguished to insert and attach prostheses in the recipient bone: impaction into bone, primary mechanical interlocking, cement fixation, bone ongrowth and secondary mechanical interlocking with bioinert materials, and enhanced bone ongrowth and bone bonding to bioactive materials. The resulting typical histomorphologies of orthopedic and dental prostheses-bone interfaces are described and illustrated from the author's studies employing light, fluorescence, and backscattered electron microscopy, and corresponding microradiographs of undecalcified ground sections of bone and implants. Special emphasis is given to the mineralization-demineralization kinetics of the interfacial bone matrix interacting with specific surface reactions of some implant materials. Consequently, the distinction between bioinert and bioactive prosthetic materials is critically analyzed. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 350-355, 1998
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  • 38
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    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: hydrogel ; extracellular matrix ; neurite extension ; oligopeptide ; tissue engineering ; guidance channel ; nerve regeneration ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Growing neurites are guided through their environment during development and regeneration via different cellular and extracellular matrix (ECM) molecular cues. To mimic cell-matrix interactions, a three-dimensional (3D) hydrogel-based ECM equivalent containing a covalently immobilized laminin oligopeptide sequence was designed to facilitate nerve regeneration. This study illustrates that the oligopeptide domain CDPGYIGSR covalently linked to an agarose gel as a bioartificial 3D substrate successfully supports neurite outgrowth from dorsal root ganglia (DRG) in vitro. The specificity of the neurite promoting activity was illustrated through the inhibition of neurite outgrowth from DRG in a CDPGYIGSR-derivatized gel in the presence of solubilized CDPGYIGSR peptide. Gels derivatized with CDPGYIGSK and CDPGRGSYI peptides stimulated a smaller increase of neurite outgrowth. In vivo experiments revealed the capability of a CDPGYIGSR-derivatized gel to enhance nerve regeneration in a transected rat dorsal root model compared to an underivatized gel, a CDPGRGSYI gel, and saline-filled nerve guidance channels. These data suggest the feasibility of a 3D hydrogel-based ECM equivalent capable of enhancing neurite outgrowth in vitro and in vivo. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 392-400, 1998.
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    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: biological tissue ; crosslinking reagent ; genipin ; subcutaneous implant ; biocompatibility ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A recognized disadvantage of the currently available chemical reagents used to fix bioprostheses is the potential toxic effects a recipient may be exposed to from residues. It is therefore desirable to provide a crosslinking reagent that is of low cytotoxicity and can form stable and biocompatible crosslinked products. To achieve this goal, a naturally occurring crosslinking reagent - genipin - was used by our group to fix biological tissues. Genipin can be obtained from its parent compound geniposide, which can be isolated from the fruits of Gardenia jasminoides ELLIS. In our previous feasibility study, it was found that the cytotoxicity of genipin is significantly lower than both glutaraldehyde and an epoxy compound. Additionally, it was shown that genipin can form stable crosslinked products. The present study further investigates the biocompatibility of a genipin-fixed porcine pericardium implanted subcutaneously in a growing rat model. The fresh, glutaraldehyde-, and epoxy-fixed counterparts were used as controls. It was noted that the inflammatory reaction of the genipin-fixed tissue was significantly less than its glutaraldehyde- and epoxy-fixed counterparts. Also, the genipin-fixed tissue has tensile strength and resistance against in vivo degradation comparable to the glutaraldehyde-fixed tissue. Additionally, the calcium content of the genipin-fixed tissue measured throughout the entire course of the study was minimal. Nevertheless, further study in calcification for the genipin-fixed tissue should be conducted in a blood-contact environment. The results obtained in this subcutaneous study indicate that genipin is a promising crosslinking reagent for biological tissue fixation. However, further durability testing in vitro and in vivo are needed to determine the relative functional merits of this new crosslinker. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 568-576, 1998.
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  • 40
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    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: gene therapy ; immunoisolation ; human growth hormone ; β-glucuronidase ; factor IX ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Microencapsulation of recombinant “universal” cells with immunoprotective membranes is an alternate approach to somatic gene therapy. Therapeutic gene products secreted by these cells can be delivered to different patients without immunosuppression or genetic modification of the host's cells. The encapsulation of different mammalian cell types (epithelial cells, fibroblasts, and myoblasts) is compared among three alginate-based microcapsules: (1) calcium-linked alginate microcapsules with a solubilized core and a poly-L-lysine-alginate-laminated surface; (2) barium-linked alginate beads with a gelled core; and (3) a hybrid formulation of barium-linked alginate beads with a poly-L-lysine-alginate-laminated surface. The mechanical stability of the different microcapsule types, as measured with a cone-and-plate shearing apparatus, was superior in the two barium-linked alginate beads. All cell types maintained high viability (65-90%) in culture after encapsulation. The recombinant gene products secreted by these cells (human growth hormone MW = 22,000, human factor IX MW = 57,000, and murine β-glucuronidase MW = 300,000) were able to traverse the three microcapsule types at similar rates. Cell numbers within the microcapsules increased twofold to 〉 20-fold over 4 weeks, depending on the cell type. Epithelial and myoblast cell numbers were not affected by microcapsule formulation; however, fibroblasts proliferated the most in the calcium-linked alginate spheres. These results show that for culturing fibroblasts in a mechanically stable environment the classical calcium-linked microcapsules are adequate. However, where mechanical stability is a more critical requirement, the solid barium-linked gelled beads are more appropriate choices. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 587-596, 1998.
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  • 41
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The stability of plasma-polymerized allylamine films with autoclaving sterilization cycles was investigated. Polymerized films were deposited under pulsed plasma conditions using two different duty cycles to provide surfaces having different initial amino group concentrations. The film properties were analyzed by XPS and water contact angle measurements before and after autoclaving. The reactions of these surfaces with trifluoroacetic anhydride provided quantitation of the amino surface concentrations before and after autoclaving. In general, the plasma-polymerized films exhibit good stability vis à vis the autoclaving process, with relatively high retention of the surface amino groups. The results of this work are of specific value with respect to tissue culture studies in which surface modifications involving the introduction of amino groups have been shown to have high efficacy in promoting cell growth. The results obtained suggest that the simple one-step plasma treatment process is a viable alternative to the more cumbersome surface modification procedures currently employed to introduce amino groups in these tissue culture studies. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 597-603, 1998.
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  • 42
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    Hoboken, NJ : Wiley-Blackwell
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    Keywords: platelets ; biomaterials ; platelet-derived microparticles ; procoagulant activity ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Platelet activation is an inevitable consequence of blood-material interactions. The ability of those activated platelets and platelet-derived microparticles to enhance coagulation reactions leading to thrombin/fibrin formation has not been well studied despite its potential significance. Activated platelets and platelet-derived microparticles are known to dramatically enhance the catalytic efficiencies of the tenase and prothrombinase complexes. In this paper, a modified Russell viper venom coagulation time test is used to quantitate material-induced procoagulant activity due to the generation of activated phospholipid surfaces. In our test system, polyethylene and Silastic tubes were filled with heparinized whole blood and left to gently flow back and forth at 37°C. After 1 h, the blood within the tubes was gravity drained and the plasma fraction assayed for procoagulant activity. The clotting times were determined by a Coag-A-Mate X2 instrument after the automated addition of Russell viper venom (to activate factors V and X) and calcium ions. Appreciable procoagulant activity was generated during whole blood contact within polyethylene and Silastic tubes although significantly greater activity was generated by the latter surface. As previously reported, platelet-derived microparticles also were detected by flow cytometry. Filtration of the plasma after material contact through a 0.1 μm filter led to substantial gains in clotting times and to near complete removal of microparticles, indicating that the material-induced microparticles likely were responsible for the procoagulant activity. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 611-616, 1998.
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  • 43
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    Keywords: NiTi shape memory alloy ; stents ; surface treatments ; corrosion resistance ; surface characterization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Because of its good radiopacity, superelasticity, and shape memory properties, nickel-titanium (NiTi) is a potential material for fabrication of stents because these properties can facilitate their implantation and precise positioning. However, in vitro studies of NiTi alloys report the dependence of alloy biocompatibility and corrosion behavior on surface conditions. Surface oxidation seems to be very promising for improving the corrosion resistance and biocompatibility of NiTi. In this work, we studied the effect on corrosion resistance and surface characteristics of electropolishing, heat treatment, and nitric acid passivation of NiTi stents. Characterization techniques such as potentiodynamic polarization tests, scanning electron microscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy were used to relate corrosion behavior to surface characteristics and surface treatments. Results show that all of these surface treatments improve the corrosion resistance of the alloy. This improvement is attributed to the plastically deformed native oxide layer removal and replacement by a newly grown, more uniform one. The uniformity of the oxide layer, rather than its thickness and composition, seems to be the predominant factor to explain the corrosion resistance improvement. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 433-440, 1998
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  • 44
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    Keywords: surface plasmon resonance ; atomic force microscopy ; protein adsorption ; block copolymer ; Pluronics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Pluronic surfactants, PEO-PPO-PEO triblock copolymers, have been investigated widely due to their protein-resistant properties in applications as coatings for implants and in controlled drug release systems. We have studied a wide range of these copolymers, varying in both PEO and PPO block size, by adsorbing them to a polystyrene surface and investigating their subsequent resistance to human serum albumin adsorption. This investigation has been carried out in real time, using surface plasmon resonance, with the surfaces subsequently visualized by atomic force microscopy. This approach has allowed determination of the effect of the lengths of the PEO and PPO polymer chains on protein resistivity. For low-molecular-weight Pluronics a significant, yet not complete, reduction in albumin adsorption has been observed whereas higher molecular weight Pluronics appear to completely inhibit adsorption within the time frame of this experiment. An increase in the PPO block size of the copolymer also appears to increase its protein resistance. This work further confirms that the binding strength of the anchoring block to the hydrophobic surface, rather than the length of the protruding hydrophillic PEO chains, determines a copolymer's protein resistance capability. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 165-171, 1998.
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  • 45
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    Keywords: protamine filter ; chemical amplification ; CNBr activation ; protamine immobilization ; heparin adsorption ; poly-L-lysine conjugation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We previously reported the development of a cellulose fiber based blood filter device containing immobilized protamine (termed protamine filter) that could be used to control both heparin- and protamine-induced complications during extracorporeal therapy. To achieve enhanced heparin adsorption on the fibers, we examined the possibility of utilizing the poly-L-lysine based amplification method to augment protamine loading on the fiber, as well as to create multiple layers of immobilized protamine for heparin interaction. Results show that such a method yielded about a threefold increase in protamine loading and, consequently, about a fourfold enhancement in heparin adsorption when compared with the control without poly-L-lysine amplification. This technological improvement may facilitate development of a new generation of protamine filters with capacity and efficacy suitable for various clinical applications in extracorporeal heparin removal. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 182-187, 1998.
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  • 46
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    Keywords: cartilage ; tissue engineering ; confocal laser scanning microscopy ; hyaluronic acid ; bioresorbable materials ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The aim of this study was to investigate the possibility of using the benzyl ester of hyaluronic acid (HYAFF® 11), a recently developed semisynthetic resorbable material, as a scaffold for the culture of human nasoseptal chondrocytes in tissue-engineering procedures of cartilage reconstruction. Different techniques such as immunohistochemistry, scanning electron microscopy, and confocal laser scanning microscopy were used to study the behavior, morphology, and phenotype expression of the chondrocytes, which were initially expanded and then seeded on the material. The nonwoven cell carrier allowed good viability and adhesivity of the cells without any surface treatment with additional substances. Furthermore, the cultured cells expressed cartilage-specific collagen type II, indicating that they were able to redifferentiate within the scaffold of HYAFF® 11 and were able to retain a chondrocyte phenotype even after a long period of in vitro conditions. Nevertheless, the expression of collagen type I, which was produced by dedifferentiated or incompletely redifferentiated chondrocytes, was noticeable. Additional data were obtained by subcutaneous implantation of samples seeded with human cells in the in vivo model of the athymic nude mouse. The results after 1 month revealed the development of tissue similar to hyaline cartilage. This study is promising for the use of this scaffold for tissue engineering of cartilage replacements. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 172-181, 1998.
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  • 47
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    Keywords: endothelial cell ; ePTFE vascular graft ; plasma deposition ; pulsatile flow ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We sought to examine whether surface modification of expanded polytetrafluoroethylene (ePTFE) vascular grafts might extend graft patency without modifying the graft structure. Amide and amine plasma (butylamine) were applied to graft surfaces using radio frequency glow discharge. Surface analyses by Fourier transform infrared spectroscopy-attenuated total reflectance, X-ray photoelectron spectroscopy, and dynamic contact angle measurements revealed the presence of nitrogen-containing functional groups on the plasma modified graft surfaces, along with an increased surface hydrophilicity. Bovine aortic endothelial cells were seeded on amide and amine plasma coated ePTFE vascular grafts and placed inside an artificial circulatory system under well-defined flow conditions. The seeded endothelial cells were exposed to either constant or pulsatile flow condition for 5 days. Their corresponding maximum wall shear stresses were 1 dyn/cm2 under constant flow and 65, 108, and 259 dyn/cm2 under various pulsatile flows. Plasma modified ePTFE vascular grafts enhanced the endothelial cell lining under constant and pulsatile flow conditions. Fluorescence nuclear staining, scanning electron microscopy, and histological staining indicated the formation of an endothelial cell monolayer on the plasma coated graft surfaces. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 188-198, 1998.
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  • 48
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    ISSN: 0021-9304
    Keywords: alginate beads ; in vitro ; chondrocytes ; differentiation ; biomaterials ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Chondrocytes from 21-day-old rat fetal nasal cartilage were cultured in alginate beads for up to 20 days. It was found that chondrocytes retained their spherical shape and typical chondrocytic appearance. During the culture time, chondrocytes underwent differentiation, as demonstrated by the alkaline phosphatase-specific activity and rate of proteoglycan synthesis. Morphological data confirmed chondrocyte differentiation with the appearance of hypertrophic chondrocytes scattered in the alginate gel and a dense extracellular matrix containing filamentous structures and matrix vesicles. In addition, Northern blot analysis performed on day 8 of culture showed that chondrocytes cultured in alginate beads expressed type II collagen mRNA. The alginate bead method also appeared to be suitable for testing biomaterials, and the ready dissolution of the alginate beads by chelating agents provided a simple means for the rapid recovery of encapsulated chondrocytes. Powdered glass-ceramic particles entrapped in the alginate gel were colonized by chondrocytes, which then proliferated and formed a tissue similar to a true calcified cartilaginous structure. These results indicate that the alginate system represents a relevant model for studies of chondrogenesis and endochondral ossification. Furthermore, the encapsulation method could prove useful for studies of tissue-biomaterial interactions in an in vitro environment which more closely mirrors the cartilage matrix than other culture methods. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 213-222, 1998.
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  • 49
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    ISSN: 0021-9304
    Keywords: osteoblast-like cells ; mineralization ; stainless steel corrosion products ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of this study was to investigate the effects of 316L stainless steel (SS) corrosion products on the in vitro biomineralization process, because tissue necrosis, bone loss, impaired bone mineralization, and loosening of orthopedic implants are associated with ions and debris resulting from biodegradation. Rat bone marrow cells were cultured in experimental conditions that favored the proliferation and differentiation of osteoblastic cells and were exposed to SS corrosion products obtained by electrochemical means for periods ranging from 1 to 21 days. Quantification of total and ionized Ca and P, as well as Fe, Cr, and Ni, ions in the culture media of control and metal added cultures during the incubation period was performed to study the influence of corrosion products on the Ca and P consumption that occurs during the mineralization process. Control cultures and metal effects on cultures were evaluated concerning DNA content, enzymatic reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and alkaline phosphatase (ALP) activity. Histochemical detection of ALP, Ca, and phosphate deposition, and examination of the cultures by scanning and transmission electron microscopy (SEM and TEM) were also performed. The presence of SS corrosion products resulted in impairment of the normal behavior of rat bone marrow cultures. Levels of Cr and Ni in the medium of cultures exposed to 316L SS corrosion products decreased throughout the incubation period, suggesting a regular deposition of these species; these results were supported by TEM observation of the cultures. Cultures exposed to the corrosion products presented lower DNA content, MTT reduction, and ALP activity and failed to form mineralized areas. These cultures showed negative staining on histochemical reactions for the identification of calcium and phosphate deposition and SEM and TEM examination did not show mineral globular structures or mineralization foci, respectively, which is characteristic of cultures grown in control conditions. These results suggest that metal ions associated with 316L SS are toxic to osteogenic cells, affecting their proliferation and differentiation. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 199-212, 1998.
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  • 50
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    Keywords: biocompatibility ; glass-ceramic ; bone marrow cells ; osteoblast ; osteoclast ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Previous studies have shown different macrophage responses to three compact pellets (with slightly different chemical composition) of gel-derived bioactive glass-ceramics of the CaO-P2O5-SiO2 system. In the present study primary bone marrow cells directed in vitro to form osteoblastic or osteoclastic cells were cultivated on glass slides coated by these three glass-ceramics. Glass slides were used as controls. In osteoblastic cultures alkaline phosphatase activity varied, depending on the type of coatings. Northern analysis showed high mRNA expressions of bone-related proteins on both the glass-ceramics and control glass. Mineralized nodules were not formed on the control glass, but coating glass slides with the glass-ceramics promoted mineralization without any substantial differences between the types of coatings. In osteoclastic cultures, the normal morphology of tartrate resistant acid phosphatase-positive multinucleated cells on standard culture plates was altered on the control glass and the glass-ceramics. The number of these cells differed, depending on the type of coatings, with no particular differences in the arrangement of F-actin by these cells. These analyses demonstrate complete biocompatibility of the glass-ceramic coatings but not the control glass, on which the cells failed to form mineralized nodules. The phenotype expression of the cells appeared to be influenced by microstructure, surface roughness, and the general character of the coatings rather than their surface reactivity. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 433-442, 1998.
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  • 51
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    Keywords: ζ potential ; wear particles ; inflammatory synovial fluid ; polymethyl methacrylate (PMMA) ; ultrahigh molecular weight polyethylene (UHMWPE) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This study was undertaken to determine the ζ potentials of particulate biomaterials in three types of protein-rich hyaluronan solution with changes in pH; a microelectrophoretic method was used. For the purpose of determining the pH value of synovial fluid in various inflammatory conditions, we collected synovial fluid samples from joints with osteoarthritis (OA), rheumatoid arthritis (RA), and those undergoing revisions arthroplasties. The mean values of the pH in the synovial fluid from joints with OA, RA, and revision arthroplasty were shown to be 7.9, 7.5, and 8.1, respectively. The pH-ζ potential curves obtained differed, depending on the biomaterial and the medium. Addition of γ-globulin to the medium reduced the absolute value of the ζ potentials of some of the biomaterials. The findings of this study suggest that the electrophoretic behaviors of the particulate biomaterials tested in this study are affected by the protein constituents of and pH changes in protein-rich synovial fluid. The values we obtained will be useful as reference standards and will also aid in the study of the surface phenomena of biomaterials. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 453-457, 1998.
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  • 52
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    Keywords: endothelial cells ; heavy metals ; cell adhesion molecules (CAMs) ; signal transduction ; protein kinases ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Heavy metal ions can be released by corroding metallic implants into the surrounding tissue. When they enter blood vessels some of them are carried by proteins like albumin and can be taken up by endothelial cells lining the vessels. To study their involvement in the inflammatory response we investigated heavy metal ion induced effects in cultured human vascular endothelial cells (HUVECs). NiCl2 and CoCl2 upregulate, especially in concentrations of 1 mM, the expression of adhesion molecules (e.g., E-selectin and intercellular adhesion molecule-1), as well as the cytokines IL-6 and IL-8, as shown by enzyme immunoassay and Northern blot analysis. In addition, possible signal transduction mechanisms were elucidated. The HUVECs were treated with various selective inhibitory drugs followed by the incubation of metal ions before measuring the expression of the above-mentioned endothelial factors. Two protein kinase inhibitors (H-7 and H-8) strongly repressed Ni2+ and Co2+ enhanced expression, as did the phospholipase A2 inhibitor quinacrine. Other selective inhibitors of protein kinases C or A, or cGMP-dependent protein kinases, as well as calcium antagonists like 1,2-bis(2-aminophenoxy)ethan-N,N,N′,N′-tetraacetic acid and 3,4,5-trimethoxybenzosäure 8-(diethylamino)-octylester and inhibitors of receptor mediated endocytosis (primary amines), had no influence. We showed that NiCl2 and CoCl2 activate the translocation of the transcription factor nuclear factor (NF)-κB into the cell nucleus and enhance its binding to a NF-κB consensus sequence as shown by mobility shift analysis. Furthermore, we demonstrated the activation of AP-1. Despite the repression of heavy metal induced adhesion molecule synthesis, we did not detect any inhibition of NF-κB translocation by H-7 or H-8. Therefore, it must be concluded that heavy metal ions like Ni2+ and Co2+ activate two or more signal transduction pathways in endothelial cells. We clearly showed that there is one pathway in which H-7 and H-8 sensitive protein kinases are involved and a second pathway leading to NF-κB activation, which is insensitive to H-7 and H-8. Our results demonstrate that heavy metal ions induce mechanisms of gene activation in endothelial cells as do proinflammatory mediators, indicating that corroding metal ion containing biomaterials can provoke inflammatory reactions by known, as well as by yet unknown, intracellular signaling pathways. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 443-452, 1998.
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  • 53
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    ISSN: 0021-9304
    Keywords: hydroxyapatite ; fluorapatite ; tricalcium phosphate ; kinetics ; hydrolysis ; fluoridation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Although there is interest in forming synthetic analogs of hard tissues at physiologic temperature, significant gaps in knowledge exist with respect to the mechanisms by which precursor solids convert to apatites and also with respect to the apatite compositions that may be formed. In this study calcium-deficient HAp [Ca9(HPO4)(PO4)5OH] was prepared by hydrolysis of tricalcium phosphate (TCP), α-Ca3(PO4)2. The kinetics of HAp formation were studied as a function of temperature by isothermal calorimetry. TCP hydrolyzed completely within about 12 h, and the hydrolysis reaction evolved 133 kJ/mol of HAp formed. Although the kinetics of hydrolysis exhibited a strong temperature dependence, the mechanistic path taken appeared independent of temperature. The fluoridation of hydroxyapatite compositions having Ca/P ratios higher than 1.59 previously has been investigated. However, little work has been done on the fluoridation of more calcium-deficient hydroxyapatite. Ca9(HPO4)(PO4)5OH was formed at temperatures between 37.4° and 55°C to vary its morphology. These preparations then were reacted in NaF solution and the kinetics of fluoride incorporation studied. Solution chemical analyses were used to determine the amounts of fluoride incorporated. The extent of hydroxyl replacement by fluoride ranged from 17 to 72% and correlated with the surface area of the parent HAp. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 458-464, 1998.
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 55
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 56
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    ISSN: 0021-9304
    Keywords: dental composite ; fracture toughness ; elastic modulus ; hardness ; strength ; aging ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of this study was to evaluate the long-term effect of aging in water on the physical properties of experimental composites having systematically controlled differences in degree of conversion (DC), filler volume fraction (Vf), and percentage of silane-treated fillers. Composites were made with a 50% Bis-GMA:50% TEGDMA light-cured resin and a 1-2 μm (average size) strontium glass filler (+ 5 wt% SiO2 microfiller). For composites A-E, the DC was varied from 56-66% by changing the curing time; for D and F-I, the Vf was varied from 28-62 vol%; and for D and J-M, the percent of fillers with a silane coupling agent (γ-MPS) was varied from 20-100%. Fracture toughness (KIc), flexure strength (FS), elastic modulus (E), and hardness (KHN) were tested after soaking in water at 37°C for 1 day, 6 months, 1 year, and 2 years. The KIc was reduced 20-30% for all composites after 6 months, with minimal changes thereafter. The FS was reduced for several composites at 6 months, but only those with poor cure (A and B) were lower at 2 years than they were initially. The E was not reduced for most composites. Hardness was reduced for most composites after 6 months, but many returned to their original levels at 2 years. Long-term aging in water caused a reduction in the KIc, independent of composition, but had little effect on other properties, suggesting limited degradation of composites in water. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 465-472, 1998.
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  • 57
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    Keywords: polyglycolide ; biodegradability ; implant ; microstructure ; porosity ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The solid-state polymerization of halogenoacetates leads quantitatively to polyglycolide (polyglycolic acid) and an eliminated metal halide. Washing out this salt leaves highly porous polyglycolide (total pore volume about 50%) with pore sizes in the submicron range. Thorough examination of the product with different methods (DSC, IR, and X-ray diffraction) gave no indication of any remaining halogenoacetate. This distinct micromorphology should be advantageous for its application as a biomaterial. Special features of porous polyglycolide are an inherent surface roughness, a high specific surface, a higher gas permeability, and a lower density compared to conventionally prepared polyglycolide. The control over these properties should allow a fine-tuning of the biocompatibility of polyglycolide. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 83-88, 1998
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    Keywords: gelatin ; films ; tissue ; bonding ; argon beam ; Chemistry ; Polymer and Materials Science