bluuebunny/crossref_metadata_2025_split huggingface dataset:
Competitive adsorption of vitronection with albumin, fibrinogen, and fibronectin on polymeric biomaterials
Authors: Fabrizius‐Homan D. J. , Cooper S. L. 
Published: December 2004

AbstractVitronectin (VN) was competitively adsorbed with human serum albumin (HSA), fibrinogen (FGN), and fibronectin (FN) from binary component mixtures in order to compare the relative affinities of these proteins for various polymer materials. Competitive adsorption was monitored by incubating radiolabeled protein solutions inside 0.125‐in. i.d. tubing of the polymers, flushing with buffer, and measuring the adherent radioactiviy. Adsorption experiments at equal mass concentrations of the competing proteins revealed that VN comprises at least 75% by weight of the adsorbed protein when competitively adsorbed with HSA and approximately 50% by weight when competitively adsorbed with FGN and FN on all surfaces except a poly(ethylene oxide)‐based polyurethane where it comprised closer to 80 wt%. When VN was competitively adsorbed in the presence of increasing amounts of HSA, FGN, and FN, the amount of VN adsorbed on a weight basis was diminished the most by FGN. HSA had the least inhibitory effect at low bulk concentrations and FN had the weakest effect at higher bulk concentration levels. When HSA, FGN, and FN were competitively adsorbed in the presence of increasing amounts of VN, VN diminished their adsorption on a weight basis in the order: HSA > FN > FGN.
Histologic evaluation of the osseous adaptation to titanium and hydroxyapatite‐coated titanium implants
Authors: Jansen J. A. , van de Waerden J. P. C. M. , Wolke J. G. C. , De Groot K. 
Published: December 2004

AbstractThe aim of this study was to obtain more information about the bone reaction to titanium and hydroxypatite (HA)‐coated titanium implants during the first 3 months after implantation. Therefore, uncoated and coated implants were inserted into the tibia of rabbits for various implantation periods. The histological results demonstrated that although there were no marked differences in bony reaction at the cortical level to the different implant materials, HA‐coating appeared to induce more bone formation in the medullary cavity. It was also noted, that 3 months after insertion loss of coating thickness had occurred.
The bonding behavior of calcite to bone
Authors: Fujita Yoshitsugu , Yamamuro Takao , Nakamura Takashi , Kotani Seiya , Ohtsuki Chikara , Kokubo Tadashi 
Published: December 2004

AbstractPlates of calcite (CaCO3) were implanted in rabbit tibiae, and their biocompatibility and bonding ability to bone were studied. The plates were also implanted subfascially in rabbit muscle for 8 weeks, and changes on their surfaces in the body were examined. Contact microradiography and Giemsa surface stain demostrated direct bonding between calcite and bone without interpositions. The average failure load of the interface between calcite and bone was 4.11 kg, indicating an adequate strength of bonding. However, a Ca‐P‐rich layer, which formed on the surfaces of other bioactive ceramics in vivo, was not detected by a scanning electron microscope‐electron probe x‐ray microanalyzer. Scanning electron micrographs of the surface of calcite implanted subfascially for 8 weeks showed marked degradation and a rough surface. However, the surface apatite layer was not detected by thin‐film x‐ray diffraction analysis and Fourier transform infrared reflection spectroscopy. Calcite is a biodegradable material that bonds to bone without a surface apatite layer. The mechanical bonding provided by the anchoring effect of the newly formed bone into the surface roughness of calcite is considered to be a major factor in calcite‐bone bonding.
Combined chemical and mechanical effects on free radicals in UHMWPE joints during implantation
Authors: Jahan M. S. , Wang C. , Schwartz G. , Davidson J. A. 
Published: December 2004

AbstractAn electron spin resonance (ESR) technique is employed to determine the free radical distribution in the articulating surfaces of retrieved acetabular cups and knee‐joint plateaus (retrieved after more than 6 years of implantation). Similar measurements made on samples prepared from cyclically stressed and unstressed cups, and on samples following oxidations in nitric acid and intralipid solutions provided sufficient data to gain more knowledge about the combined chemical and mechanical effects on PE free radicals during implantation. In UHMWPE free radicals are primarily initiated by gamma‐ray sterilization; however, during implantation, peroxy (scission type) free radicals are formed and reach a maximum concentration level (equilibrium state) due to oxidation by chemical (hemoglobin and/or synovial fluids) environment of the joints. Subsequently, due to frictional heating and stress in the loading zones, free radical reaction is accelerated and their number is reduced only in those areas. This is consistent with the observations of a temperature rise in acetabular cups duringin vitrofrictional wear stress tests andin vivotelemetry observations, as reported by others. Compared with the previously reported SEM micrographs the low‐free‐radical regions are correlated with high‐wear areas and the high‐free‐radical regions with the low‐wear areas.
A new canine model for evaluating blood prosthetic arterial graft interactions
Authors: Brophy Colleen M. , Ito Ralph K. , Quist William C. , Rosenblatt Michael S. , Contreras Mauricio , Tsoukas Athanassios , Logerfo Frank W. 
Published: December 2004

AbstractVarious models have been proposed to examine blood‐prosthetic materials interactions in terms of the effect of the prosthetic material on platelet structure and function, blood coagulation and fibrinolysis, and tissue infiltrates (cellular or acellular). In addition, these modeles have been used to examine the change in the graft surface over time. Particular difficulties in examining graft‐materials interactions include species differences, short residence time for blood‐materials interactions with commonly employed short grafts, and length of study limitations with ex vivo shunts. In this paper we report a canine, carotid‐aorta subcutaneous prosthetic graft model. The specific advantages of this model are the length of the graft, which allows prolonged contact of blood with the prosthetic surface; the subcutaneous location of the graft, which allows repeated sampling of blood along the graft; and the healing characteristics of canine grafts. We selected the canine model because the healing characteristics are morphologically similar to those in humans in that endothelialization of the prosthetic surface is limited. Other models, such as the pig, are favored for use when examining blood coagulation, platelet, or fibrinolytic studies; however, these models can fully endothelialize prosthetic surfaces.
Evaluation of polyphosphates and polyphosphonates as degradable biomaterials
Authors: Richards M. , Dahiyat B. I. , Arm D. M. , Brown P. R. , Leong K. W. 
Published: December 2004

AbstractA series of polymers, bisphenol A‐based poly(phosphoesters), were evaluated as degradable biomaterials. Degradation was observed for the four polymers studied under both in vitro and in vivo conditions. The rate of degradation was affected by polymer side‐chain structure and correlated with the swelling behavior. The ethyl side‐chain polymers absorbed more water than their phenyl counterparts. Among the sterilization methods, UV irradiation followed by antibiotic treatment was the most suitable, as steam autoclave and ethylene oxide treatments altered the properties of several of the poly(phosphoesters). Tissue response to the poly(phosphoesters) in rabbits was characterized by minor encapsulation and slight or no lymphocyte, giant cell, or macrophage activity. No evidence of edema or necrosis was found. The elastic moduli of these materials varied from 488 MPa for poly(bisphenol A‐ethylphosphate) (BPA/EOP) to 627 MPa for the more rigid poly(bisphenol A‐phenylphosphonate) (BPA/PP). The ultimate strength, modulus, and energy to failure of BPA/PP were lower than those of similarly compression molded high‐molecular‐weight poly(L‐lactic acid) (PLLA).
Synthesis and bioactivity of copolymers with fragments of heparin
Authors: Mazid M. A. , Moase E. , Scott E. , Hanna H. R. , Unger F. M. 
Published: December 2004

AbstractA new type of biocompatible copolymer comprising small fragments of heparin, (octa‐ to dodecasaccharides) copolymerized with a synthetic monomeric component, viz. acrylamide, has been prepared. The heparin fragments are produced by enzymatic or chemical means and are copolymerized, directly or after suitable derivatization, with acrylamide as the major polymerizable component. The polymeric material incorporates the heparin segments as pendant moieties such that their essential functional groups and structural features for specific binding with the selective serine protease coagulation factor inhibitor antithrombin III are preserved. An important feature of this copolymer is its biocompatibility which relates specifically to its antithrombotic and antithrombogenic activity derived from those of heparin fragments. The biological activity of heparin fragments and copolymers thereof are determined in terms of APTT and anti‐Xa activity, their antithrombotic potential being expressed as a ratio of anti‐Xa activity to APTT. The copolymers reported have biological activities similar to equivalent amounts of respective heparin fragments, and show higher antithrombotic activity compared to intact heparin or commercially available low‐molecular‐weight heparin (4,000–6,000 Da).
Student research award in the hospital intern, resident or clinical fellow Category, 17th Annual Meeting of the Society for Biomaterials, scottsdale, AZ May 1–5,1991. A new biological membrane for pericardial closure
Authors: Muralidharan S. , Gu Jiang , Laub Glenn W. , Cichon Romuald , Daloisio Connie , McGrath Lynn B. 
Published: December 2004

AbstractIn an attempt to develop a new and better biological membrane for the pericardium, we evaluated the use of glutaraldehyde treated human amniotic membrane (AM) and compared it to polytetraflouroethylene (PTFE) membrane as a pericardial substitute. Four dogs underwent a right thoracotomy. Two 4 × 3‐cm portions of pericardium, 3–4 cm apart, were excised in each animal and both sites replaced with a similar sized patch of 0.8% glutaraldehyde‐treated AM and 0.2‐mm PTFE membrane respectively. The AM was sutured to the pericardial defect with its smooth surface facing the epicardium. After 18 weeks, the materials were evaluated. The AM patches revealed minimal extrapericardial and no epicardial adhesion. The PTFE patches had moderate to severe epicardial adhesions and severe extrapericardial adhesions. Histopathological examination of AM patches revealed that the integrity of the AM was preserved, however, neovascularization and slight lymphocytic infiltration were observed. In the PTFE patches, there were severe inflammatory infiltration and fibroblast proliferation into both surfaces. AM patches by virtue of their low immunogenicity evoke very minimal host to graft reaction. These AM grafts, however, tear easily unless carefully sutured. Improved methods of treatment may improve suturing strength. We conclude that AM performs satisfactorily and is superior to PTFE as a pericardial substitute.
NIR‐spectroscopic investigation of water sorption characteristics of dental resins and composites
Authors: Venz S. , Dickens B. 
Published: December 2004

AbstractA near infrared (NIR) method using the 5200 cm−1 absorption of water has been employed to examine water absorbed in photopolymerized dental resins and composites in the form of 0.01‐cm‐to 0.15‐cm‐thick specimens. The concentration, c [mol L−1], of absorbed water in specimens of thickness t [cm] was calculated by means of Beer's law, A = ϵct. A is the NIR absorbance and ϵ is the absorptivity of absorbed water. ϵ depends on the environment of the water molecule and it is necessary to estimate ϵ for water in each material. Water sorption was determined gravimetrically and correlated to the absorbance in the NIR spectrum. Once the relationship between ϵ and water content was known for a material, water sorption was determined rapidly on very thin specimens for faster equilibration. Where dissolution of the specimen occurred, the solubility behavior of the specimen was evaluated from a comparison of NIR and gravimetric measurements. The NIR absorptivity, ϵ, of water absorbed in a polymeric medium was found to be inversely related to the degree of hydrophilicity and hydrogen bonding capability of the polymer. The presence of water clusters in a polyethylene oxide methacrylate polymer was inferred from convex‐up curvature in the plot of ϵ vs. water content.
In vivo characterization of the inflammatory properties of poly(tetrafluoroethylene) particulates
Authors: Kossovsky Nir , Millett David , Juma Saad , Little Nancy , Briggs Preston C. , Raz Schlomo , Berg Eric 
Published: December 2004

AbstractSuburothelial injections of particulate poly(tetrafluoroethylene) (PTFE) is becoming a widely accepted treatment for a number of urological disorders. Because little is known about the long‐term histologic morphology of the injection site, this animal study was performed. Three populations, each consisting of two mongrel dogs, five New Zealand White rabbits, and 10 BALB/c mice, were injected with poly(tetrafluoroethylene) particulate in a glycerine carrier (Polytef Paste) and were followed for a period of 1 week, 3 months, 6 months, and 1 year. Mice received one subcutaneous dorsal injection each, rabbits received two subareolar injections each, and dogs received three subareolar injections each in addition to two periurethral injections. Histologic examination of the biopsy sites revealed a persistent chronic inflammatory reaction with progressive growth of the involved tissue volume. In addition to giant cells and macrophages, lymphocytes became apparent at 3 months and constituted up to 40% of the cellular infiltrate by 1 year. Plasma cells were also noted at the 1‐year period in the rabbit model. The progressive growth of the inflammatory pseudotumors evoked by injected PTFE may compromise the long‐term safety of certain urological procedures involving particulate PTFE.
Synthesis and nonthrombogenicity of polyetherurethaneurea film grafted with poly(sodium vinyl sulfonate)
Authors: Ito Yoshihiro , Iguchi Yuichiro , Kashiwagi Takashi , Imanishi Yukio 
Published: December 2004

AbstractSynthesis of nonthrombogenic materials without using biologically active substances was explored. Poly(sodium vinyl sulfonate) is a water‐soluble synthetic polymer and activates antithrombin III to exert nonthrombogenicity that was dependent on the molecular weight. Polyetherurethaneurea film was plasmatreated and graft‐polymerized with sodium vinyl sulfonate. The graft film showed excellent in vitro and ex vivo nonthrombogenicity by suppressing interactions with plasma proteins and platelets as well as by inactivating bloodclotting factors.
Physical and blood‐contacting properties of polyurethanes based on a sulfonic acid‐containing diol chain extender
Authors: Okkema A. Z. , Visser S. A. , Cooper S. I. 
Published: December 2004

AbstractPolyurethanes chain extended with N,N‐bis (2‐hydroxyethyl)‐2‐aminoethanefulfonic acid (BES) were synthesized. The effect of the sulfonic acid group on the polymers' bulk, surface, and bloodcontacting properties was evaluated by comparing the BES‐based polymers with polyurethanes based on N‐ethyldiethanolamine (EDEA). In addition, the effect of soft‐segment polarity was addressed by comparing polyurethanes based on polyetetramethylene oxide (PTMO) (MW = 1000) with polymers based on polyethylene oxide (PEO) (MW = 1000). The EDEA control samples had physical properties similar to a viscous fluid. The presence of the sulfonic acid group dramatically enhanced the degree of microphase separation and the mechanical strength of all the polymers. The more polar PEO soft segment resulted in polymers which were more phase mixed than the PTMO‐based polyurethanes. Surface characterization studies revealed that in vacuum, all the surfaces were enriched in the polyether soft‐segment phase. After 24‐h equilibration in water, all the surfaces had similar surface polarities independent of the SO3H content. The canine ex vivo blood‐contacting results showed that the sulfonic acid group in the PTMO‐based polymers significantly reduced the number and activation of the adherent platelets. Fibrinogen deposition, however, increased with increasing sulfonic acid content. In contrast, platelet and fibrinogen deposition on the sulfonic acidcontaining PEO‐based polymers was greatly enhanced.
Asymmetric membrane filters for the removal of leukocytes from blood
Authors: Bruil A. , Van Aken W. G. , Beugeling T. , Feijen J. , Steneker I. , Huisman J. G. , Prins H. K. 
Published: December 2004

AbstractAs part of a study on the mechanisms of leukocyte filtration, the influence of pore size distribution on filter efficiency was investigated. Conventional leukocyte filters are not suitable for model studies, as these filters are composed of tightly packed synthetic fibers, with a poorly defined porous structure. Therefore, open cellular polyurethane membranes with pore size distributions varying from approximately 15 to 65 μm were prepared. Filtration experiments with stacked packages of these membranes showed that leukocytes are best removed (>99%) by filters with a pore size distribution of 11–19 μm. These pore sizes approach the size of leukocytes (6–12 μm). However, due to fast clogging, blood flow through these filters is rapidly reduced, which results in a low filter capacity. With an asymmetric membrane filter, in which the pore size decreases from about 65 to 15 μm in the direction of blood flow, both moderate removal of leukocytes (>80%) and maintenance of flow (∼0.2 mL/s) are obtained. This results in efficient leukocyte removal. From cell analysis of both filtrate and filter, it is concluded that adhesion rather than sieving is the major filtration mechanism. Thus, further optimization of the filter may be achieved by surface modification.
Water‐curable and biodegradable prepolymers
Authors: Kobayashi Hisatoshi , Hyon Suong‐Hyu , Ikada Yoshito 
Published: December 2004

AbstractIn an attempt to develop biodegradable polymers which can be shaped in situ and adhere to living tissues, we synthesized esterurethane prepolymers which can be cured upon contact with water in living tissues. First, D,L‐lactide polymerization or D,L‐lactide‐ϵ‐caprolactone (50:50) co‐polymerization was carried out using ethylene glycol or poly(ethylene glycol) as initiator to obtain hydroxyl‐terminated biodegradable polyesters. They were then reacted with an excess of diisocyanate such as hexamethylene diisocyanate, toluylene diisocyanate, and diphenylmethane diisocyanate to introduce a reactive isocyanate group to both of the end groups of the polyesters. The isocyanate‐terminated prepolymers could be cured in the presence of water and the cured polymers were degraded by hydrolysis both in vitro and in vivo. It was found that the presence of appropriate amounts of hydrophilic units in the main chain was essential for giving a high curing rate and a high degradation rate for the biodegradable urethane prepolymers. The tissue responses to the cured polymers were not severe.
Lysine‐enhanced glutaraldehyde crosslinking of collagenous biomaterials
Authors: Simionescu Agneta , Simionescu Dan , Deac Radu 
Published: December 2004

AbstractCrosslinking of collagenous biomaterials currently employs the use of glutaraldehyde. The putative enhancement of glutaraldehyde crosslinking by lysine was investigated in three model systems: bovine pericardium, collagen membranes, and bovine serum albumin. Repetitive sequential treatment of bovine pericardium with glutaraldehyde and lysine and finally with formaldehyde produced a matrix which, by the two criteria used (shrinkage temperature and urea/SDS soluble collagen), was shown to be more highly crosslinked than pericardium fixed in glutaraldehyde alone. Essentially the same results were obtained when membranes prepared from pepsin‐soluble pericardial collagen were subjected to sequential glutaraldehyde and lysine treatments, reaching shrinkage temperatures of more than 90°C. Heart valves prepared from lysineenhanced glutaraldehyde crosslinke bovine pericardium were tested in vitro in an accelerated fatigue tester and have been shown to behave satisfactorily after 300 million cycles. These additional crosslinks proved to be stable in saline at 37°C. Studies on bovine serum albumin attempted to get an insight into the mechanisms of lysine enhancement of glutaraldehyde crosslinking by treating sequentially albumin with glutaraldehyde and lysine and analysis of the products by gel filtration and SDS‐PAGE. These studies suggest that free amino groups exposed by proteins are initially reacted with glutaraldehyde and the bridged by the diamino compound (lysine) producing more extensive intermolecular crosslinking than glutaraldehyde alone.
Acoustic emission during fatigue of porous‐coated Ti‐6Al‐4V implant alloy
Authors: Kohn David H. , Ducheyne Paul , Awerbuch Jonathan 
Published: December 2004

AbstractAcoustic emission (AE) events and event intensities (e.g., event amplitude, counts, duration, and energy counts) were recorded and analyzed during fatigue loading of uncoated and porous‐coated Ti‐6A1‐4V AE source location, spatial filtering, event, and event intensity distributions were used to detect, monitor, analyze, and predict failures. AE provides the ability to spatially and temporally locate multiple fatigue cracks, in real time. Fatigue of porous‐coated Ti‐6A1‐4V is governed by a sequential, multimode fracture process of: transverse fracture in the porous coating; sphere/sphere and sphere/substrate debonding; substrate fatigue crack initiation; slow and rapid substrate fatigue crack propagation. Because of the porosity of the coating, the different stages of fracture within the coating occur in a discontinuous fashion, There‐fore, the AE events generated are intermittent and the onset of each mode of fracture in the porous coating can be detected by increases in AE event rate. Changes in AE event rate also correspond to changes in crack extension rate, and may therefore be used to predict failure. AE offers two distinct advantages over conventional optical and microscopic methods of analyzing fatigue cracks–it is more sensitive and it can determine the time history of damage progression. The magnitude of the AE event intensities increased with increasing stress. Failure mechanisms are best differentiated by analyzing AE event amplitudes. Intergranular fracture and microvoid coalescence generated the highest AE event amplitudes (100 dB), whereas, plastic flow and friction generated the lowest AE event amplitudes (55–65 dB). Fractures in the porous coating were characterized by AE event amplitudes of less than 80 dB.