bluuebunny/crossref_metadata_2025_split huggingface dataset:
Peptide, protein, and cellular interactions with self‐assembled monolayer model surfaces
Authors: Margel S. , Vogler E. A. , Firment L. , Watt T. , Haynie S. , Sogah D. Y. 
Published: December 2004

AbstractModel biomaterial surfaces with well defined chemistry were prepared from close‐packed alkyltrichlorosilane monolayers on polished silicon and glass. The outermost molecular groups which come in direct contact with the biological environment were varied across a wide range of oxidation states by employing CF3, CH3, CO2CH3, and CH2OH terminal functionalities. Characterization by contact angles, surface spectroscopy, and ellipsometry verified that these model surfaces could be repeatedly prepared with good consistency for routine use to study biomolecule adsorption onto model surfaces. Adhesion of canine endothelial cells and the adsorption of proteins (human serum albumin and human fibrinogen) as well as a series of synthetic defined oligopeptides to these model surfaces have been studied. Endothelial cells attachment and growth were in the rank order of: CH2OH > CO2Me > CH3 > CF3. The peptides were comprised of different alternating sequences of lysine, leucine, and tryptophan residues. These structural differences imparted different amphiphilic characters that led to measurable differences in the adsorption of these peptides to liquid‐vapor interfaces. The adsorption to model surfaces was studied using ESCA, radiometry, and concentration‐dependent contact angles. ESCA and radiometry measured irreversible biomolecules adsorption whereas the contact angle method measured steadystate adsorption. Radiometric results were inconsistent with ESCA, possibly due to artifacts associated with protein radiolabeling. © 1993 John Wiley & Sons, Inc.
Solution effects on the surface reactions of three bioactive glass compositions
Authors: Filgueiras M. Regina T. , La Torre Guy , Hench Larry L. 
Published: December 2004

AbstractThe in vitro five‐stage surface reactions of two bioactive glass compositions, 45S5 and 52S4.6, and one bioinert glass, 60S3.8, exposed to three simulated body fluids (SBF) were analyzed using Fourier Transform infrared Spectroscopy (FTIR). There was little effect of SBF composition on ion exchange, silica hydrolysis, and silica polymerization (stages 1–3) of glass with silica content up to 52 wt%. However, calcium and phosphate ions in SBF accelerated the formation of an amorphous calcium‐phosphate (a‐CP) layer (stage 4), and crystallization (stage 5) of the hydroxycarbonate apatite (HCAp) layer. The magnesium ions had a retardation effect on the kinetics of stages 4 and 5, but little effect on stages 1–3. In SBF solutions which contained calcium and phosphate ions an amorphous calcium‐phosphate (a‐CaP) layer formed on even a 60S3.8 glass which was not bioactive in vivo. However, the a‐CaP layer did not crystallize to form HCAp. Thus, there is a significant contribution from the ions present in the SBF solutions to the HCAP formation and crystallization of HCAp on bioactive glasses. Also, silanol repolymerization is necessary for rapid crystallization of HCAp. © 1993 John Wiley & Sons, Inc.
Structure and integrity of a plasma sprayed hydroxylapatite coating on titanium
Authors: Whitehead R. Y. , Lacefield W. R. , Lucas L. C. 
Published: December 2004

AbstractPlasma sprayed hydroxylapatite (HA) coatings on titanium substrates were analyzed for process‐induced compositional and structural changes. The HA starting powder and the resulting HA coatings were characterized using x‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The integrity of the ceramic‐to‐substrate bond strength was also determined, by subjecting plasma sprayed HA coatings to shear/cantilever bond testing. The ceramic coatings retained the basic apatitic crystal structure of the starting powder; however, a considerable amount of amorphous material was created during the plasma spray process. FTIR and Raman spectroscopy revealed that the resulting coatings were partially dehydroxylated. Both XRD and FTIR spectroscopy results also suggested that amorphous material, as well as additional calcium phosphate phases such as α‐tricalcium phosphate (TCP) not in the starting powder, were present in the HA coating. Average bond strengths of the HA coatings to Ti were determined to be 14.8 MPa +/− 3.5, with fracture occurring at the interface and within the coating itself. © 1993 John Wiley & Sons, Inc.
Tissue reactions to subcutaneously implanted, surface‐modified silicones
Authors: Okada Toshiyuki , Ikada Yoshito 
Published: December 2004

AbstractTo evaluate the influence of surface properties on tissue reactions, the surface of a medical‐grade silicone elastomer was modified without changing the bulk properties. Surface modifications employed were oxidation by corona discharge in air, graft polymerization of watersoluble monomers, coating a polysaccharide through polyion complex formation, and covalent immobilization of cell‐adhesive proteins. Surface‐modified silicone sheets were implanted in the subcutaneous tissue of rats, and tissue reactions such as infiltration of inflammatory cells, appearance of foreign‐body giant cells, and collagenous capsule formation were studied. It was found that the thickness of collagenous capsules formed after 16 weeks' implantation was in the range of 85–95 μm for the nontreated ones and all the modified silicones except the acrylic acid‐grafted and the collagen‐immobilized silicones. © 1993 John Wiley & Sons, Inc.
In vivo corrosion of modular hip prosthesis components in mixed and similar metal combinations. The effect of crevice, stress, motion, and alloy coupling
Authors: Gilbert Jeremy L. , Buckley Christine A. , Jacobs Joshua J. 
Published: December 2004

AbstractOne hundred forty‐eight retrieved modular hip prostheses of both mixed (Ti‐6Al‐4V/CoCr) and similar (CoCr/CoCr) metal combinations were examined and positive evidence of corrosive attack was found in the conical taper region between head and stem. Significant corrosion was observed in both mixed and similar metal combinations with 16% of necks and 35% of heads (for mixed‐metal cases), and 14% of necks and 23% of heads (for similar‐metal cases) showing moderate to severe corrosive attack. There was a significant correlation between the percentage of prostheses with moderate to severe corrosion and the duration of implantation for both mixed and similar metal cases, indicating that this corrosion process is progressive in time. Moderate to severe corrosion was seen as early as 2.5 and 11 months (mixed and similar metals, respectively).Scanning electron microscopy and x‐ray analysis identified several forms of corrosive attack in the cobaltbased component of the taper. These included, for both mixed and same metal combinations: preferential dissolution of cobalt, fretting, and pitting; mixed metals only: the formation of a Ti‐Cr‐Mo interfacial phase and interdendritic corrosion; and for similar metals: intergranular attack adjacent to grain boundaries enriched in molybdenum and silicon. It is hypothesized that the restricted crevice environment, coupled with high cyclic stresses which cause repeated fracture of the passive oxide films in the taper, result in an unstable electrochemical environment within the crevice for both the cobalt alloy and Ti‐alloy passive films. The passivity of these alloys is subsequently lost and active attack of the taper results. Also, the repeated fracturing of the passive films will result in large amounts of corrosion products being formed. This corrosion and particulate accumulation could result in loss of mechanical integrity of the implants in vivo, create particles for third body wear, and release particles into the surrounding tissues. © 1993 John Wiley & Sons, Inc.
Optimization of extruded collagen fibers for ACL reconstruction
Authors: Dunn Michael G. , Avasarala Prashanti N. , Zawadsky Joseph P. 
Published: December 2004

AbstractCollagen fibers used in a scaffolding device for ligament reconstruction must be thin, strong, and degradable. The purpose of this study was to determine the effects of fiber diameter (20, 50, or 90 μm), crosslinking agent (uncrosslinked, dehydrothermal‐cyanamide, or glutaraldehyde), and hydration on the initial mechanical properties, biocompatibility, and subcutaneous degradation rates of fibers extruded from an acidic dispersion of insoluble type I collagen. The wet tensile strength of extruded collagen fibers was significantly improved by decreasing the fiber diameter. Lowdiameter, crosslinked fibers had wet tensile strengths ranging from 75–110 MPa. In contrast, high diameter fibers had wet strength values of about 30 MPa. The degradation rate of the implanted fibers, in contrast, was not significantly prolonged by changing the initial fiber diameter. This result is important because prolonged degradation of the fibers can lead to implant encapsulation instead of neoligament formation. By minimizing the diameter, fiber stregth can be increased without prolonging the fiber degradation rate. Low‐diameter, dehydrothermal‐cyanamide crosslinked fibers have greater tensile strength and a more rapid degradation rate than medium‐diameter, glutaraldehyde crosslinked fibers, and are therefore more suitable for use in a degradable ligament reconstruction device. © 1993 John Wiley & Sons, Inc.
The effect of phagocytosis of poly(L‐lactic acid) fragments on cellular morphology and viability
Authors: Lam K. H. , Schakenraad J. M. , Esselbrugge H. , Feijen J. , Nieuwenhuis P. 
Published: December 2004

AbstractThe aim of this study was to investigate the effect of phagocytosed poly(L‐lactic acid) particles on the morpholgy and viability of phagocytes, mainly macrophages. Therefore, predegraded poly(L‐lactic acid) (P‐PLLA) and nontreated PLLA (N‐PLLA) particles, both having diameters not exceeding 38 μm, were injected intraperitoneally in mice. P‐PLLA particles were obtained by 25 kGy γ‐irradiation of N‐PLLA particles. N‐PLLA and P‐PLLA particles were injected using an 0.3% ethanol/0.9% saline solution intraperitoneally to the mice. We also studied the release of the absorbed ethanol as a possible model for the release of low molecular weight, potentially toxic products. As control, nondegradable polytetrafluoroethylene (PTFE) particles and the carrier solution were used. After 1, 2, 3, 4, 5, and 7 days, the cells of the abdominal cavity were harvested to study the effect of phagocytosis of polymer particles on phagocytic cell morphology and viability. Studies with transmission electron microscopy indicated that, upon injection of particles in the peritoneal cavity, macrophages demonstrated signs of cell damage, cell death, and cell lysis due to phagocytosis of a large amount of P‐PLLA particles. The morphology of the cells that had phagocytosed the N‐PLLA and PTFE particles did not differ substantially from those of control animals in which only the solution was injected. Also, in the controls, hardly any cell death and no debris was observed. When the PLLA particles were injected as a suspension in a 0.3% ethanol/0.9% saline solution, no difference was observed between N‐PLLA and P‐PLLA. After phagocytosis, both cause cell damage, sometimes leading to cell death. The highest numbers of necrotic cells were observed on day 2. The effects could be caused by the (peak) release of degradation products from P‐PLLA fragments or by the release of the absorbed ethanol when the 0.3 ethanol/0.9 saline solution was used to administer the particles. In conclusion, it can be stated that cell damage, sometimes leading to cell death, may be caused by phagocytosed poly(L‐lactic acid) particles. © 1993 John Wiley & Sons, Inc.
Lack of inhibition of adhesion of an enteropathogenic Escherichia coli by polycarbophil
Authors: Mack David R. , Blain‐Nelson Penny L. , Mauger John W. 
Published: December 2004

AbstractAnionic polyacrylic acid polymers, such as polycarbophil, have a number of properties that would make them suitable carriers for sustained antibiotic release formulations in the intestinal tract. However, little is known with regards to possible microbial adhesion to polycarbophil. The aim of this study was to evaluate for such an interaction using the rabbit enteric pathogen Escherichia coli RDEC‐1 (serotype 015:H‐). RDEC‐1 mediates attaching and effacing binding to intestinal epithelium in a manner morphologically identical to that observed in both human enteropathogenic E. coli and enterohemorrhagic E. coli infections. RDEC‐1 bacteria were grown to promote the expression of the mannose‐resistant AF/R1 adhesion pili. A nonpiliated mutant, strain M34, was used as a negative control. Using radioactive labeling of bacteria, we quantitated adhesion of piliated RDEC‐1 in the presence of polycarbophil using an in vitro adhesion assay system. Binding of piliated RDEC‐1 in the adhesion assay was greater than for nonpiliated M34 for all concentrations of bacteria greater than 109 (P < .05). Polycarbophil did not cause concentration‐dependent inhibition of piliated RDEC‐1 binding (P > .05). We conclude polycarbophi does not interfere with the AF/R1 adhesin ligand of RDEC‐1. Use of this polymer as a mucoadhesive drug delivery vehicle for nonabsorbable antibiotics in the treatment of gastrointestinal infections would not be expected to interfere with the protective effects of intestinal mucins. © 1993 John Wiley & Sons, Inc.
Cellular response to well‐characterized calcium phosphate coatings and titanium surfaces in vitro
Authors: Ong J. L. , Prince C. W. , Lucas L. C. 
Published: December 2004

AbstractThe cellular response to well‐characterized Ca‐P and Ti surfaces was analyzed. This study indicated that the ion‐beam sputtering process could produce a hydroxyapatite‐type coating. However, structural alterations such as the incorporation of CO3 and the loss of the OH groups were observed. The Ti surfaces were shown to be predominantly amorphous TiO2. The in vitro cell culture study showed no significant differences in cell number for the Ti and Ca‐P surfaces throughout the 12‐day study. Furthermore, the initial percentage of protein within the cell layers was significantly lower for cells on Ca‐P surfaces compared with the cell layer on Ti surfaces. However, after 3 h incubation, no significant difference in the percentage of protein was observed for the Ti and Ca‐P surfaces. © 1995 John Wiley & Sons, Inc.
Improvement of blood compatibility on cellulose dialysis membrane. III. Synthesis and performance of water‐soluble cellulose grafted with phospholipid polymer as coating material on cellulose dialysis membrane
Authors: Ishihara Kazuhiko , Miyazaki Hideki , Kurosaki Toshikazu , Nakabayashi Nobuo 
Published: December 2004

AbstractTo improve the surface blood compatibility on a cellulose hemodialysis membrane, a blood compatible polymer with a phospholipid polar group, poly[2‐methacryloyloxyethyl phosphorylcholine(MPC)], was immobilized on the surface through the coating of a water‐soluble cellulose grafted with poly(MPC) (MPC‐grafted cellulose, MGC). The MGC was synthesized by graft copolymerization of MPC on a water‐soluble cellulose using cerium ion as an initiator. The coating process on the cellulose membrane with and aqueous solution of the MGC was convenient, and the MGC on the surface was not significantly detached even after immersion in water. The permeability and mechanical strength of the membrane coated with the MGC did not decrease compared with the original membranes. The MGC‐coated cellulose membrane was blood compatible, as determined by the prevention of platelet adhesion and aggregation after contact with platelet‐rich plasma. From these results, it is concluded that the MGC may be a useful material for improving the blood compatibility of the cellulose hemodialysis membrane. © 1995 John Wiley & Sons, Inc.
Silicone breast implants: The role of immune system on capsular contracture formation
Authors: Granchi Donatella , Cavedagna Daniela , Ciapetti Gabriela , Stea Susanna , Schiavon Patrizia , Giuliani Renzo , Pizzoferrato Arturo 
Published: December 2004

AbstractWe evaluated the role of the immune system in the pathogenesis of the periprosthetic capsular contracture, the most frequently occurring complication following the implant of silicone prostheses. Peripheral blood samples from 22 patients with silicone‐gel‐filled implants were examined. In all cases a capsule was felt by palpation, and it was classified according to the Baker scale. Ten patients (group 1) had a Baker 2 contracture, and 12 (group 2) had severe contracture rated 3 and 4. The cells positive to antigens CD3, CD4, CD8, HLA‐DR, CD19, CD25, CD57, CD16, and CD14, and the cytotoxic activity of the lymphocytes on target cells K562 were assessed by cytofluorimetric analysis. At time 0 there were no statistically significant differences between patients and normal subjects, nor between the two groups. At 48 h, the group 2 patients had a number/mm3 of cells CD57 + significantly higher than both group 1 and control group (P < .05). In group 1 patients, the cytotoxic activity was similar to that of normal subjects, whereas in group 2 it was significantly increased, in respect to both the controls (P < .05) and group 1 (P < .001). In all groups, the contact of the lymphocytes with the silicone extract did not modify either the antigen expression or the lymphocyte functional activity. On the basis of these results we hypothesize the involvement of the immune system in the formation of the capsular contracture around the prosthesis. © 1995 John Wiley & Sons, Inc.
Nitric acid passivation of Ti6A14V reduces thickness of surface oxide layer and increases trace element release
Authors: Callen B. W. , Lowenberg B. F. , Lugowski S. , Sodhi R. N. S. , Davies J. E. 
Published: December 2004

AbstractPassivation of Ti6Al4V and cpTi implants using methods based on the ASTM‐F86 nitric acid protocol are used with the intention of reducing their surface reactivity, and consequently the corrosion potential, in the highly corrosive biologic milieu. The ASTM‐F86 passivation protocol was originally developed for surgical implants made of stainless steel and chrome cobalt alloy. Using X‐ray photoelectron spectroscopy (XPS) to examine the effect of nitric acid passivation on the surface oxide layer of mill‐annealed Ti6Al4V and cpTi, we have found that such treatment actually reduced the oxide thickness on the alloy while having no significant effect on the pure metal. These results correlated with observations obtained using graphite furnace atomic absorption spectrophotometry (GFAAS) to detect trace element release from solid, mill‐annealed, Ti6Al4V and cpTi into serum‐containing culture medium. We detected significantly greater levels of Ti, Al, and V in the presence of passivated compared to nonpassivated Ti6Al4V. In contrast, nitric acid passivation did not influence Ti release from mill‐annealed Ti‐based metals, would indicate that re‐examination of ASTM‐F86‐based passivation protocols with respect to Ti6Al4V should be considered in view of the widespread use of this alloy for biomedical devices. © 1995 John Wiley & Sons, Inc.
Fracture toughness determination of dental materials by laboratory testing and finite element models
Authors: Pidaparti Ramana M. V. , Beatty Mark W. 
Published: December 2004

AbstractThis study assessed the effectivenness of finite element analysis in predicting the stress intensity factor (KIC) for three types of dental materials: a glass ionomer, a dental amalgam, and a composite resin. Laboratory tests were conducted on small single‐edge notch specimens loaded in three‐point bending to determine values for fracture toughness (KQ). Using the dimensions measured for each laboratory specimen, a J integral approach was employed to calculate KIC using finite element analysis. Both two‐dimensional plane strain and three‐dimensional models were used in determining KIC for each specimen, and these values were compared to the KQ values obtained from laboratory tests. The results indicated that no significant differences existed between laboratory results and those obtained from both two‐ and three‐dimensional finite element models (P > .85). For the three‐dimensional model, values for KIC were found to vary across the specimen thickness, with the values at the center of the specimen closely paralleling those obtained from the two‐dimensional plane strain J integral technique was as effective as the three‐dimensional technique in calculating values for KIC. © 1995 John Wiley & Sons, Inc.
Oxidative biodegradation mechanisms of biaxially strained poly(etherurethane urea) elastomers
Authors: Schubert Mark A. , Wiggins Michael J. , Schaefer Michael P. , Hiltner Anne , Anderson James M. 
Published: December 2004

AbstractAs part of ongoing studies in polyurethane biostability and biodegradation, we have investigated an in vitro system to test strained poly(etherurethane urea) (PEUU). Recently, we utilized this system to reproduce in vivo stress cracking in strained Pellethane®. In this study, strained PEUU was tested to determine whether it degrades through a common mechanism with Pellethane® and to further examine the steps involved in this degradation.Biaxially strained PEUU elastomers were treated with an α2‐macroglobulin (α2‐Mac) protein solution followed by an oxidative H2O2/CoCl2 treatment. Characterization of the strained PEUU specimens was performed with attenuated total reflectance‐Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), electron spectroscopy for chemical analysis, and contact angle analysis. The results from these characterization techniques provide conclusive evidence that biodegradation of PEUU and Pellethane® occurs through a common mechanism. Chemical changes to the PEUU include cleavage of the polyether soft segments and urethane linkages, leaving the hard segment domains unaffected. SEM analysis shows that this chain cleavage leads to the development of severe pitting and cracking of the PEUU surface. In addition, the in vitro degradation accurately reproduces the in vivo degradation chemically and physically. This result verifies that the primary species responsible for biodegradation of PEUUs, in vivo, are hydroxyl and/or hydroperoxide radicals. α2‐Mac pretreatment increases the rate of degradation compared to direct treatment in H2O2/CoCl2. As the PEUU soft segment chains are cleaved, the degradation products are extracted into the treatment solution or environment. Finally, a new biodegradation mechanism of PEUUs is presented that involves crosslinking of the polyether soft segments. © 1995 John Wiley & Sons, Inc.