bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of FRP composite structural biomaterials: Fatigue strength of the fiber/matrix interfacial bond in simulatedin vivoenvironments
Authors: Latour R. A. , Black J. 
Published: December 2004

AbstractFiber/matrix interfacial bonding in fiber reinforced polymer (FRP) composite materials is potentially sensitive to degradation in aqueous environments. Ultimate bond strength (UBS) in carbon fiber/polysulfone (CF/PSF) and polyaramid/polysulfone (K49/PSF) was previously reported to be significantly decreased in two simulatedin vivoenvironments. While UBS is a useful parameter, for orthopedic implant applications the fatigue behavior of the interface is probably a more relevant indicator of long‐term composite material performance. In this article, the effects of simulatedin vivoenvironments (saline, exudate) upon the fatigue behavior of the interface of CF/PSF and K49/PSF are reported. The fatigue behavior of both material combinations was linearly dependent on the logarithm of fatigue life in the dry (control), saline, and exudate environments. Testing either material in saline and exudate resulted in significantly lower fatigue strength than in the dry environment; however, results in the two wet environments were indistinguishable. The CF/PSF interface experienced fatigue failure at approximately 105load cycles at a maximum applied load level of only 15% of its ultimate dry bond strength without indication of a endurance limit being reached. These results raise some important questions regarding the durability of CF/PSF composite in load bearing orthopedic applications. © 1993 John Wiley & Sons, Inc.
Quantification of the edge effect in calcified bioprosthetic tissues
Authors: Wika Kent E. , Utoh Junichi , Brown Joy , Harasaki Hiroaki 
Published: December 2004

AbstractIn bioprosthetic tissue samples that had been implanted in the subcutaneous space of rats, and recurring pattern of calcification was observed. In this pattern, which we call the edge effect, the interior of the tissue is calcified and is surrounded and separated from the subcutaneous fluid by a zone that is free from calcification. The edge effect has been qualitatively described in the literature for subcutaneous implants and for valve leaflets, and it may be related to the mechanism of calcification for these materials. The thickness of the calcification free outer layer was quantified for glutaraldehyde treated bovine pericardium, glycerol treated bovine pericardium, glutaraldehyde treated human dura mater, and glycerol treated human dura mater. The edge effect values were found to be unique and consistent for each material type, and they were inversely related to the shrinkage temperatures and the calcium contents of the materials. It was determined that the chemical treatment was more important than the tissue type in determining the edge effect value. © 1993 John Wiley & Sons, Inc.
Chemical durability of Y2O3‐Al2O3‐SiO2 glasses for the in vivo delivery of beta radiation
Authors: Erbe Erik M. , Day Delbert E. 
Published: December 2004

AbstractMicrospheres made from Y2O3‐Al2O3‐SiO2 (YAS) glasses, which contain radioactive Y‐90, are currently being used to treat liver cancer in humans, where their chemical durability is of prime importance. In deionized water or saline at 37°C, the weight percent Yttrium (Y) dissolved from eight different YAS glasses ranged from only 0.02–0.13% of the total Y present and their dissolution rate was barely measurable, ≤ 1.0 × 10−9 g/cm2‐min. The most chemically durable YAS glass was 17Y2O3‐19Al2O3‐64SiO2, mol %. The small amount of Y released from microspheres, 25–35 μm diameter, of this glass after corrosion in saline or deionized water at 37°C was essentially the same as for bulk glass samples. Based on their excellent chemical durability, it is concluded that YAS glass microspheres are suitable for in vivo use. © 1993 John Wiley & Sons, Inc.
The shear strength and the failure mode of plasma‐sprayed hydroxyapatite coating to bone: The effect of coating thickness
Authors: Wang B. C. , Lee T. M. , Chang E. , Yang C. Y. 
Published: December 2004

AbstractPlasma‐sprayed hydroxyapatite coated (HAC) 50 and 200 μm thick on Ti‐6Al‐4v cylinders was transcortically implanted in the femora of canines to to evaluate in detail the effect of coating thickness on the pushout shear strength and failure mode examined under scanning electron microscope after the periods of 4, 6, 8, and 12 weeks. The HAC coating exhibited higher shear strength at 50 μm than at 200 μm. Its failure mode was conclusively at or near the HAC–bone interface, and the slight attack of body fluid had not degraded the implant to the extent that failure occurred at the HAC‐Ti alloy interface after 12 weeks of observation. For 200 μm‐HAC, failure was found at the HAC–bone interface, inside the HAC lamellar splat layer and at the HAC‐Ti alloy substrate interface, depending on the period of implantation. It was also deduced that the variation of failure mode of 200 μm‐HAC with time could not be accounted for by the attack of body fluid alone; the degradation must be a synergetic adverse result of residual stress in the HAC and the attack of body fluid. © 1993 John Wiley & Sons, Inc.
Bicomponent vascular grafts consisting of synthetic absorbable fibers. I. In vitro study
Authors: Yu Tarng‐Jenn , Chu C. C. 
Published: December 2004

AbstractThe objective of this study is to determine the effects of the location and concentration of synthetic absorbable yarn components in bicomponent vascular graft fabrics on their structure and properties in a controlled in vitro hydrolytic environment. Bicomponent vascular fabrics were made from Dacron and polyglycolic acid (PGA) yarns with a range of composition ratios of PGA to Dacron and a range of locations of PGA. Both woven and single jersey knit fabrics were made. These fabrics were characterized by standard textile methods and subject to in vitro hydrolytic degradation study. In vitro hydrolytic degradation study showed that the most dramatic changes in the bicomponent fabric characteristics and properties occurred 30 and 60 days of hydrolysis. This schedule coincided with the hydrolytic degradation rate of PGA absorbable sutures. In the woven (W) group, the incorporation of absorbable yarns in the weft direction (W3) of the bicomponent fabrics resulted in the velour‐like, loose, and porous surface morphology of the fabric for potential subsequent tissue ingrowth, while those woven fabrics with absorbable yarns in the warp direction (W1) did not have this unique velour‐like surface. In the knitted (K) group, the concentration of absorbable yarns appeared to be closely related to the observed changes in fabric properties and structure. The incorporation of absorbable yarns into knitted fabrics did not result in the same level change in fabric structure and property as woven fabrics. In both W and K groups, a minimal level of mechanical strength of the fabrics was maintained due to the remaining Dacron yarns. Structural integrity of these fabrics was retained at the end of hydrolytic degradation study. The data obtained could be used to correlate with the subsequent in vivo performance of these bicomponent vascular grafts. If correlations exist, they could be used to improve the design of future bicomponent vascular grafts for improved performance. © 1993 John Wiley & Sons, Inc.
Degradation of polyurethane foams used in the mêcme breast implant
Authors: Benoit Frank M. 
Published: December 2004

AbstractThe release of toluene diisocyanate derivatives from polyurethane foam covers that were removed from the Měme breast implant was studied. The polyurethane foam covers as retrieved from the implants were contaminated on average with 2,4‐ and 2,6‐toluene diamine (TDA), 2,4‐ and 2,6‐toluene diisocyanate (TDI), and toluene isocyanate amine (TIA) at the 1086 ppm level (combined TDA, TDI, and TIA). When cleaned foam was incubated in Ringer's solution at 37°C for periods ranging from 6–35 days, 4.6 ppm/day of TDA, TDI, and TIA (combined) was formed; the projected annual degradation rate of the foam under these conditions was estimated to be about 0.8%. When cleaned foam was incubated dry at 37°C, 1.5 ppm/day of TDA, TDI, and TIA (combined) was produced. Hence, the polyurethane foam covers used in the Měme breast implants are susceptible to both thermal and hydrolytic degradation under simulated physiological conditions. © 1993 John Wiley & Sons, Inc.
Endothelial cell compatibility testing of three different Pellethanes
Authors: Bordenave L. , Baquey Ch. , Bareille R. , Lefebvre F. , Lauroua C. , Guerin V. , Rouais F. , More N. , Vergnes Ch. , Anderson J. M. 
Published: December 2004

AbstractThere is a need for viable small diameter vascular grafts, the luminal surface of which could be seeded by endothelial cells (ECs) to prevent thrombosis. In order to select candidates for EC seeding before implantation, the in vitro cytocompatibility of three different Pellethanes® (polyetherurethanes) using human ECs was investigated. The methodology included two stages depending on either direct contact between cells and materials or contact between cells and material extracts, obtained under standardized conditions. By the latter method, we observed a cytotoxic effect on cell growth with 2363‐55 D Pellethane extract at a 50% (v/v) concentration in the nutrient medium, likely provoked by leachables and correlated with the lowest levels of tPA, PAI1, and vWF antigens in the supernatants. By the former method, we studied EC attachment and growth. Morphology was studied by classical means and completed by scintigraphy and microautoradiography after 111Indium‐labeling of the EC monolayer. Differentiation was determined by the release of vWF antigen and measurement of vWF activity (multimeric organization) after human thrombin stimulation. Despite an inhibition of proliferation for both 55 D and 75 D types (compared to the control), a functional monolayer of ECs was obtained on 75 D. Pellethane 75 D could be the best support for in vitro endothelialization. © 1993 John Wiley & Sons, Inc.
Osteogenic differentiation of marrow stromal stem cells in porous hydroxyapatite ceramics
Authors: Ohgushi Hajime , Dohi Yoshiko , Tamai Susumu , Tabata Shiro 
Published: December 2004

AbstractBioactive materials such as hydroxyapatite ceramics (HA) are known to show a stable interfacial bond with tissues (the bone bonding property has been especially well documented). However, the biological phenomenon on the material surface that evoke bone bonding is not well documented. To address this issue, composites of porous HA and rat marrow cells were implanted into ectopic (subcutaneous) sites. At 3 weeks after implantation, active osteoblasts lining the HA surface initiated bone formation, primarily as mature bone (lamellar type). Gene expression study using Northern blot analysis of the composites showed that alkaline phosphatase (ALP) and bone Gla protein (BGP) mRNAs began to appear at 2 weeks and the level of BGP mRNA at 4 weeks was comparable to that of cancerous bone. However, HA implantation without marrow cells did not show bone formation and neither BGP nor ALP mRNA were detected. These results indicate that the HA surface is able to support cell differentiation (osteoblastic phenotype expression of marrow stromal stem cells), as well as cell coordination resulting in mature bone formation that bonds to the HA. © 1993 John Wiley & Sons, Inc.
Difference in bone ingrowth after one versus two daily episodes of micromotion: Experiments with titanium chambers in rabbits
Authors: Goodman Stuart , Wang Jian‐Sheng , Doshi Amol , Aspenberg Per 
Published: December 2004

AbstractMechanical stimulation has been shown to affect the differentiation and development of mesenchymal tissue. In the present study, we compared the histological and histomorphometric results of tissue ingrowth into micromotion chambers that were moved at 0 cycles per day, 20 cycles once per day, and 20 cycles twice per day over 20–30 sec, for 3 weeks. In each case, a chamber having a 1 × 1 × 5 mm square‐holed groove for tissue ingrowth was used. The total amplitude of motion was 0.75 mm. Histological sections from nonmoved chambers contained extensive trabecular bone, embedded in a fibrovascular stroma. Histomorphometric analysis disclosed that bone comprised a mean of 31 ± 2% (mean ± SEM) of the ingrown tissue. Twenty movements per day appeared to further stimulate bone ingrowth (46 ± 5%). Extensive ingrowth of more immature woven and trabecular bone was noted in a more cellular stroma. In general, increasing the degree of micromotion to 20 movements twice per day resulted in a decreased amount of bone formation (19 ± 7%). In several of these specimens, little or no bone could be found. These experiments have demonstrated that, for the parameters chosen in this study, a short daily period of low frequency, micromotion may facilitate bone ingrowth; however, when the same motion is delivered twice daily, bone ingrowth is depressed. Thus a “window” of externally applied strain appears to exist, which may facilitate or discourage tissue differentiation to bone. © 1993 John Wiley & Sons, Inc.
Inhibition of calcification of glutaraldehyde pretreated porcine aortic valve cusps with sodium dodecyl sulfate: Preincubation and controlled release studies
Authors: Hirsch Danielle , Drader Joelle , Thomas Theresa J. , Schoen Frederick J. , Levy Judith T. , Levy Robert J. 
Published: December 2004

AbstractCalcification of bioprosthetic heart valves fabricated from glutaraldehyde pretreated bovine pericardium or porcine aortic valves (PAV) is a frequent cause of the failure of these devices. Of all strategies considered thus far, only detergent preincubations using compounds such as sodium dodecyl sulfate (SDS) ingibited PAV bioprosthetic mineralization in circulatory sheep bioprosthetic valve replacements. The present study sought to characterize the mechanism of action of SDS preincubation. Results of transport and material characterization studies showed that SDS had a relatively high affinity for PAV, with a maximum uptake of 167.1 ± 6.8 μg SDS/mg tissue over 24 h at 37°C with a partition coefficient of 19.3. The PAV diffusion of SDS was 1.95 ± 0.35 10−6 cm2/sec. The principal effect of SDS on PAV was phospholipid extraction. The residual organic phospholipid extraction. The residual organic phosphate in the SDS pretreated tissue was 2.22 ± 0.72 nmol/mg tissue compared to the control untreated group with 18.52 ± 2.1 nmol/mg tissue. Incubations of PAV specimens in a 1% SDS solution for 24 h significantly inhibited calcification after 21 days in subdermal implants in 3‐week‐old male rats (PAV Ca2+ = 18.0 ± 11.8 μg/mg) compared to control (177.8 ± 6.0 μg/mg). In contrast, coimplants of 30% SDS silicone rubber polymers, for regional sustained SDS administration, did not impede PAV calcification in 21 day implants Ca2+ = 166.0 ± 14.0 μg/mg compared to the nondrug silicone matrix controls, (Ca2+ = 173.0 ± 6.6 μg/mg). Thus, we conclude that the mechanisms of SDS inhibition of PAV calcification is due to material effects which occur during preincubation, and is not facilitated by sustained SDS administration. © 1993 John Wiley & Sons, Inc.
Calcium phosphate formation within sol‐gel prepared titania in vitro and in vivo
Authors: Li Panjian , de Groot K. 
Published: December 2004

AbstractCalcium phosphate formation is induced within sol‐gel prepared titania and grows toward a calcium phosphate solution in which the titania is immersed. The implantation of this sol‐gel prepared titania film coating on TiA16V4 core into the femurs of goats shows an accumulation of calcium phosphate within the titania film 12 weeks postoperatively, which leads to the connection of the titania film coating to the bone. Therefore, sol‐gel prepared titania is probably bioactive. The results indicate that hydrated titania gel is able to generate calcium phosphate by intake of calcium and phosphate from the surrounding solution. Sufficient TiOH concentration at the titania surface is needed to start this process. Titanium could be bioactive, if its hydrolysis can be accelerated. © 1993 John Wiley & Sons, Inc.
Prevention of changes in platelet cytoplasmic free calcium levels by interaction with 2‐hydroxyethyl methacrylate/styrene block copolymer surfaces
Authors: Okano Teruo , Suzuki Ken , Yui Nobuhiko , Sakurai Yasuhisa , Nakahama Seiichi 
Published: December 2004

AbstractChanges in platelet cytoplasmic free calcium levels were investigated in contact with cast film surfaces of a block copolymer containing 2‐hydroxyethyl methacrylate (HEMA) and styrene (St) (0.5 mole fraction HEMA). These copolymer surfaces demonstrate microdomain alternating lamellae structures composed of hydrophilic HEMA domains (5 nm width) and hydrophobic St domains (20 nm width). The results were compared with those obtained from platelets contacting a random copolymer of HEMA‐St (0.5 mole fraction HEMA) and from homopolymers of polystyrene (PSt) and poly(2‐hydroxyethyl methacrylate) (HEMA). Cytoplasmic free calcium levels in platelets contacting the microdomain structured surfaces of the HEMA‐St block copolymer remained relatively constant in contrast to the significant increases observed for the radically prepared HEMA‐St copolymer, PSt, and PHEMA surfaces. Adhering platelets were stimulated by exogenously introduced thrombin and calcium ionophore A23187 20 min after platelet adherence to the polymer surfaces. Only platelets on the block copolymer surfaces showed active metabolic responses. These results suggest that adhering platelets on the microdomain structured surfaces maintain high sensitivities to external stimulation due to an intrinsic strong inhibition of platelet functional changes induced by surface contact. © 1993 John Wiley & Sons, Inc.
Hydroxylapatite supported Dacron plugs for repair of isolated full‐thickness osteochondral defects of the rabbit femoral condyle: Mechanical and histological evaluations from 6–48 weeks
Authors: Messner Karola 
Published: December 2004

AbstractThe early degeneration of neocartilage commonly observed after experimental cartilage repair is attributed in part to the impaired cartilage‐bone mechanics caused by an insufficient regrowth of the subchondral bone plate. In order to enhance bone regrowth after cartilage repair Dacron plugs supported by hydroxylapatite were implanted into 3 mm diameter full‐thickness defects of both medial femoral condyles in 21 rabbits. In addition, the plug in one knee of each animal was wrapped with autologeous periosteum from the proximal tibia. The repair sites were evaluated at 6, 12, 24, and 48 weeks. Except for the mechanics of the repair site at 24 weeks additional periosteum did not improve the overall results. In specimens with additional periosteum the compression compliance of the repair sites improved gradually from abnormal high to almost normal values at 24 weeks, but were found softened again at 48 weeks. All other repairs were softer than normal cartilage at all time intervals. In all specimens a well‐defined byt irregularly shaped, subchondral bone plate had developed by 12 weeks. The neocartilage was initially thicker than normal cartilage, but the thickness decreased gradually and reached normal values by 48 months. Neocartilage formation with moderate morphological scores appeared already at 6 weeks, but the scores did not improve with time. High variations in quality of the regenerated tissue, from insufficient regeneration to hyaline‐like cartilage, were found at all time intervals, but none of the specimens had developed normal cartilage. Most knees had a low‐grade synovitis and some had particle debris. © 1993 John Wiley & Sons, Inc.
Fibroblast anchorage to microtextured surfaces
Authors: Meyle J. , Gültig K. , Wolburg H. , von Recum A. F. 
Published: December 2004

AbstractThe contact between tissue and the implanted biomaterial is influenced by the micromorphology of the implant surface as well as biomechanical reactions. This effect is mediated by subcellular morphological structures and can affect the anchorage of the material inside the body of the host. The aim of the present study was to ascertain by transmission electron microscopy how human gingival fibroblasts interact with surface events. A special replica technique was used to produce a line pattern of 1 μm pitch with a depth of 1 μm. It was demonstrated, by transmission electron microscopy, that cells seeded on this surface extended cellular processes into the grooves, leading to an intensive contact and probably to mechanical interlocking. The typical morphological structures at several points indicated the presence of focal adhesion sites. © 1993 John Wiley & Sons, Inc.
Protein adsorption and platelet adhesion onto polyurethane grafted with methoxy‐poly(ethylene glycol) methacrylate by plasma technique
Authors: Fujimoto Keiji , Inoue Hiroyuki , Ikada Yoshito 
Published: December 2004

AbstractGraft polymerization of methoxy‐poly(ethylene glycol) methacrylate, an ester of methacrylic acid and monomethoxy‐poly(ethylene glycol) (PEO), was performed onto a polyetherurethane (PU) film and tube under different polymerization conditions by a plasma treatment technique. The surface of grafted PU film was characterized by staining with dye, x‐ray photoelectron spectroscopy, contact angle, and zeta potential. All these measurements indicated that water‐soluble chains were immobilized on the PU surface, their location being restricted to the film surface region. The PU surface showed reduced protein adsorption in vitro and reduced platelet adhesion in vitro and ex vivo. The optimum graft density suppressing the protein adsorption was as low as 5 μg cm−2. When a small amount of dimethacrylate was added to the monomer solution for graft polymerization to introduce crosslinking in the grafted layer, protein adsorption was further slightly reduced. The extent of reduction in serum albumin adsorption was always less than that of γ‐globulin. Although platelet adhesion was largely reduced by the surface graft polymerization, a definite amount of protein was always adsorbed to the grafted surface. © 1993 John Wiley & Sons, Inc.
Development of a glass reinforced hydroxyapatite with enhanced mechanical properties. The effect of glass composition on mechanical properties and its relationship to phase changes
Authors: Knowles J. C. , Bonfield W. 
Published: December 2004

AbstractUtilizing glasses of the types xNa2O‐(1−x)P2O5 and xCaO‐(1−x)P2O5 (where x = 0.2, 0.3, and 0.5), a systematic study of the effect of increasing network modifying oxides in glasses was made on the mechanical properties of a glass reinforced hydroxyapatite, at glass additions of 2.5 and 5 wt%. For the soda type glass, phase changes were promoted much more readily compared to the lime type glass. This was true for both 2.5 and 5 wt% additions of glass. For the lime type glass, considerable differences between the effects of 2.5 and 5 wt% additions were seen. At 5 wt%, the increased amount of liquid phase present promotes an increased level of phase inversion to alpha and beta tricalcium phosphate. At 2.5 wt%, a larger percentage of the HA remains stable at higher temperatures. Furthermore, the effect of the composition may be seen. As the mol% of network forming oxide increases, (i.e., the Ca/P ratio moves towards 1.67, the ratio for HA) the HA remains more stable. This is seen in the maintenance of both the HA phase and also the enhanced mechanical properties. © 1993 John Wiley & Sons, Inc.