bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic study of collagen fixation with polyepoxy fixatives
Authors: Tu R. , Lu C.‐L. , Thyagarajan K. , Wang E. , Nguyen H. , Shen S. , Hata C. , Quijano R. C. 
Published: December 2004

AbstractA new biomaterial has been developed by fixing native collagen with a polyepoxy compound (PC) fixative. In this study, bovine internal thoracic arteries were fixed with PC under various conditions to help understand the kinetics of the collagen–PC reactions and optimize the fixation process. At predetermined time intervals, small samples were cut from the arteries to determine the quantities of the remaining unreacted amino acids in the collagen. Temperature, concentration, and solution pH were among the key parameters studied. The overall fixation rate was found to be reaction‐rate controlled, as the rate of fixation was relatively slow compared with the rate of diffusion of PC. As might be expected, the reaction rate was favored by a higher temperature, concentration, and solution pH. A kinetic model, with a 2.5th reaction order with respect to the reactive functional groups of collagen and a first order with respect to PC, was developed that gave a good fit to the experimental data. Based on this model, the degree of fixation, X, as a function of time, t, is given by (1 – X)−1.5 = 1 + Kt, where K is a constant related to the intial concentrations and the reaction rate constant. © 1993 John Wiley & Sons, Inc.
Influence of mineral content and composition on graylevels in backscattered electron images of bone
Authors: Skedros John G. , Bloebaum Roy D. , Bachus Kent N. , Boyce Todd M. , Constantz Brent 
Published: December 2004

AbstractTo determine the meaning of graylevels in backscattered electron (BSE) images of actual bone tissues, the influence of mineral content and mineral composition on BSE image graylevels was studied using chick bone tissue representing a broad age range. These tissues were analyzed for BSE image graylevels, Ca/P molar ratios, mineral composition, mineral content (v/v), ash fraction (w/w), and density (g/cm3). Linear regression analyses showed that the weighted mean graylevels (WMGLs) in BSE images were positively correlated to ash fraction (r2 = 0.711), mineral content (r2 = 0.720), and density (r2 = 0.843). Although the Ca/P ratio increased from 1.65 in embryos to 1.80 in 2‐year olds, the compositional changes corresponding to this Ca/P molar ratio were estimated to produce a relatively minor (< 4.0%) change in BSE image graylevel. These results demonstrate that graylevels in BSE images of actual bone tissue can be attributed to mineral content and density, but only as a coincidence of their association with atomic number. © 1993 John Wiley & Sons, Inc.
In vitro evaluation of amorphous calcium phosphate and poorly crystallized hydroxyapatite coatings on titanium implants
Authors: Maxian Suzanne H. , Zawadsky Joseph P. , Dunn Michael G. 
Published: December 2004

AbstractStudies of various apatite coatings on metal orthopaedic prostheses suggest that coating dissolution may promote enhanced bone bonding. Little is known concerning the effect of crystallinity and the underlying roughness on calcium phosphate (Ca/P) coating dissolution rate. To address these issues, the surface chemistry of amorphous Ca/P and poorly crystallized hydroxyapatite (HA) coatings on “smooth” and “rough” titanium (Ti) alloy (Ti‐6Al‐4V) implants was studied following immersion in Hank's physiologic solution at pH 7.2 and 5.2 for 0‐, 4‐, and 12‐week periods. Changes in Calcium (Ca) ion concentrations in the solutions, coating chemistry, and surface morphology were studied by ion selective electrode, x‐ray diffraction (XRD), and scanning electron microscopy (SEM) respectively. The amount of Ca dissolved from Ca/P‐coated implants was strongly dependent on the chemistry of the coating and less dependent on pH or time of incubation. The effect of the underlying surface (smooth vs. rough) was not significant. The poorly crystallized HA coating underwent the most degradation, greatest crystallographic alteration, and greatest surface film formation. The amorphous coating was more stable in the saline environment, and may be more suitable in vivo if coating longevity is desired. These results suggest that this in vitro method is an effective way of determining difference in HA coating integrity. © 1993 John Wiley & Sons, Inc.
Human plasma α2‐macroglobulin promotes in vitro oxidative stress cracking of pellethane 2363‐80A: In vivo and in vitro correlations
Authors: Zhao Q. H. , McNally A. K. , Rubin K. R. , Renier M. , Wu Y. , Rose‐Caprara V. , Anderson J. M. , Hiltner A. , Urbanski P. , Stokes K. 
Published: December 2004

AbstractIt is hypothesized in this study that the phenomenon of environmental stress cracking (ESC) in polyetheruethane is caused by a synergistic action of biological components in the body fluids, oxidative agents, and stress. An in vitro system is designed to mimic the in vivo system; human plasma contains certain biological components that can act as a stress cracking promoter, while H2O2 (Co) solution provides an oxidative reaction comparable to that observed in the respiratory burst of adherent macrophages and foreign‐body giant cells. It is demonstrated that the phenomenon of in vivo stress cracking in Pellethane 2363‐80A is duplicated by an in vitro system that involves a pretreatment of prestressed specimens with human plasma at 37°C for 7 days followed by oxidation in 10% hydrogen peroxide with 0.10M cobalt chloride at 50°C for 10 days. The pretreatment with plasma has a synergistic effect with the oxidation by H2O2 (Co) treatment to produce ESC. A plasma component responsible for promoting stress cracking in Pellethane polyurethane is identified to be α2‐macroglobulin (α2M). © 1993 John Wiley & Sons, Inc.
Bending properties and transformation temperatures of heat treated Ni‐Ti alloy wire for orthodontic appliances
Authors: Yoneyama Takayuki , Doi Hisashi , Hamanaka Hitoshi , Yamamoto Makoto , Kuroda Takayuki 
Published: December 2004

AbstractThe effect of heat treatment temperature on bending properties and transformation temperatures of a Ni‐Ti alloy wire, 1.0 mm in diameter, was investigated so that superelasticity could be used in orthodontic appliances needing shape memory processes. The heat treatment process was at 713 K for 1.8 ks and between 673 K and 813 K for 1.8 ks. A three‐point bending test and differential scanning calorimetry were performed. The transformation temperatures of the wires were lowered with increasing heat treatment temperature. The reverse transformation finishing temperature was below the body temperature with the treatment above 753 K. Residual deflection of the Ni‐Ti wire after bending was small with the secondry heat treatment above 733 K. The load in the unloading process was less changeable and increased with the treatment temperature between 733–813 K. Secondary heat treatment in this range was suitable for using superelasticity in expansion arch appliances. © 1993 John Wiley & Sons, Inc.
Directional porosity of porcine small‐intestinal submucosa
Authors: Ferrand B. K. , Kokini K. , Badylak S. F. , Geddes L. A. , Hiles M. C. , Morff R. J. 
Published: December 2004

AbstractSmall‐intestinal submucosa (SIS) has been shown to be a promising biomaterial for vascular graft applications. This study examines the directionality property of SIS porosity using 35 SIS specimens from 13 pigs. In addition, the effects of the weight of the donor pig, preconditioning of 13 additional SIS specimens, and the duration of the test of five additional SIS specimens on such porosity are reported. The porosity from serosal to mucosal direction was found to be four times greater than the porosity in the opposite direction. The weight of the donor pig was not found to be an important factor in SIS porosity. Preconditioning served to increase the average serosal porosity index at 120 mm Hg static water pressure from 2.99 to 8.33 mL/(min cm2). The porosity in the mucosal direction was not affected by preconditioning. Porosity in both directions decreased with increasing test duration. The directionality property of SIS porosity may be an important factor in its success as a vascular graft. The term ‘porosity’ is used throughout this article, but current standards also refer to the term ‘permeability’ to describe the passage of liquid through a vascular graft. © 1993 John Wiley & Sons, Inc.
Effects of phospholipid adsorption on nonthrombogenicity of polymer with phospholipid polar group
Authors: Ishihara Kazuhiko , Oshida Hiroko , Endo Yutaka , Watanabe Akihiko , Ueda Tomoko , Nakabayashi Nobuo 
Published: December 2004

AbstractPolymers with phospholipid polar groups, 2‐methacryloyloxyethyl phosphorylcholine (MPC) polymers, have excellent nonthrombogenic properties. The effects of adsorption of phospholipids on platelet adhesion and activation on the MPC copolymer with n‐butyl methacrylate (BMA) were investigated with particular attention to the structure of the phospholipids adsorbed onto the polymer surface. The electrical nature of the phospholipids adsorbed on the polymer surface affected the thrombogenicity of the polymer. On the MPC polymer surface treated with an aqueous liposomal solution of acidic phospholipids, phosphatidylserine, platelet adhesion and activation occurred to a greater extent when compared to a poly(MPC‐co‐BMA) surface. However, on the MPC polymer surface treated with electrically neutral phosphatidylcholines, reduced thrombogenicity could be observed. Therefore, the adsorption of the phosphatidylcholines was an important factor in reducing the thrombogenicity on the polymers. Moreover, by comparison of the poly(MPC‐co‐BMA) to a poly(BMA), platelet adhesion and activation on these polymer surfaces depended on the adsorption state of the phosphatidylcholines. The amount of phosphatidylcholine adsorbed on the poly(MPC‐co‐BMA) increased with an increase in the MPC mole fraction of the copolymer. This indicates that the MPC moieties have affinity for the phosphatidylcholines. We conclude that the poly(MPC‐co‐BMA) can adsorb large amounts of phosphatidylcholines and that these phospholipids organize themselves. The organized adsorption layer of the phosphatidylcholines on the surface, which construct biomembrane‐like surfaces, can reduce platelet adhesion and activation effectively. © 1993 John Wiley & Sons, Inc.
Biocompatibility of silicon‐based electrode arrays implanted in feline cortical tissue
Authors: Schmidt Susan , Horch Kenneth , Normann Richard 
Published: December 2004

AbstractThe passive biocompatibility of silicon‐based electrode arrays was studied in feline cortical tissue. Three types of arrays were used: uncoated, coated with polyimide, and coated with polyimide over an adhesion promoter. Fifteen arrays were implanted for 24 h to determine early tissue reaction to the implantation procedure, and twelve arraays were implanted for 6 months to determine structural and material biocompatibility. Edema and hemorrhage were present around the short‐term implants, but involved less than 6% of the total area of the tissue covered by the array. With chronic implants, leukocytes were rarely present and macrophages were found around roughly one‐third of the tracks. Remnants of foreign material from the electrodes could be identified in less than 10% of the tracks. Gliosis was found around all tracks, forming an annulus between 20 and 40 μm thick. A capsule was not always present, and never exceeded a thickness of 9 μm. These results suggest that the implantation procedure produces limited amounts of tissue damage, and that the arrays are biocompatible. However, the arrays insulated with polyimide over a primer had significantly greater involvement of macrophages, gliosis, and capsule formation than uncoated arrays and arrays insulated with polyimide without printer, perhaps indicating a reaction to aluminum oxide in the primer. © 1993 John Wiley & Sons, Inc.
Effect of a combined gamma irradiation and parylene plasma treatment on the hydrolytic degradation of synthetic biodegradable sutures
Authors: Zhang Linda , Chu C. C. , Loh Ih‐Houng 
Published: December 2004

AbstractThe aim of this study was to alter the hydrolytic degradation property of synthetic absorbable suture fibers so that their mass loss would occur at a shorter time without significantly compromising their tensile strength loss profile. A two‐step treatment concept (γ‐irradiation followed by Parylene plasma deposition) was introduced for achieving this aim. Vicryl® and Maxon® were used as the model compounds to test this new concept. After the treatment, the in vitro hydrolytic degradation properties of Vicryl and Maxon were evaluated by weight loss, tensile breaking strength, heat of fusion and melting temperature, intrinsic viscosity, surface wettability, and surface morphology.The results suggested that γ‐irradiation at a dosage level between 0.2–2.0 Mrad for Vicryl sutures and about 2.0 Mrad for Maxon sutures were the most effective dosages to accelerate the suture mass loss. The subsequent Parylene plasma deposition treatment statistically significantly improved the retention of tensile strength for both γ‐irradiated Vicryl and Maxon sutures and hence counteracted the undesirable γ‐irradiation induced acceleration of tensile strength loss. However, this second‐step Parylene plasma treatment extended the suture mass loss to longer periods. These findings were consistent with the observed surface wettability, surface morphology, intrinsic viscosity, and thermal properties. A thin hydrophobic Parylene skin layer wrapped around a suture was responsible for the slower rate in mass and strength loss. This outer skin layer acted as a barrier to not only water but also degradation fragments. © 1993 John Wiley & Sons, Inc.
Effect of porous coating geometry on interfacial stress under a shear load
Authors: Wolfarth Debra , Ducheyne Paul 
Published: December 2004

AbstractPorous coated implants are loaded under both bending and shear loading. Previously, the effect of various parameters on fatigue strength under a bending load has been determined. The interfacial geometry between the porous coating and the substrate was found to increase stress concentrations leading to reduced fatigue strength. This study quantifies the effect of porous coating interfacial geometry on interfacial stress under a shear load. A two‐dimensional finite element model is used to study the effect of interfacial geometry on the value of the maximum shear stress. It was found that the requirements to reduce stress concentrations are different under a shear load than under a bending load. A conventional porous coating would require a compromise to satisfy the conflicting requirements. A new geometry, can optimize the values of the geometric parameters to satisfy the conditions for both modes of loading. © 1993 John Wiley & Sons, Inc.
Influence of ethylene oxide gas treatment on the in vitro degradation behavior of dermal sheep collagen
Authors: Damink L. H. H. Olde , Dijkstra P. J. , Van Luyn M. J. A. , Van Wachem P. B. , Nieuwenhuis P. , Feijen J. 
Published: December 2004

AbstractThe influence of ethylene oxide gas treatment on the in vitro degradation behavior of noncrosslinked, glutaraldehyde crosslinked or hexamethylene diisocyanate crosslinked dermal sheep collagen (DSC) using bacterial collagenase is described. The results obtained were compared with the degradation behavior of either nonsterilized or γ‐sterilized DSC. Upon ethylene oxide sterilization, reaction of ethylene oxide with the free amine groups of DSC occurred, which resulted in a decreased helix stability, as indicated by a lowering of the shrinkage temperature of all three types of DSC. Except for the low strain modulus the mechanical properties of the ethylene oxide sterilized materials were not significantly altered. γ‐Sterilization induced chain scission in all three types of DSC, resulting in a decrease of both the tensile strength and the high strain modulus of noncrosslinked and crosslinked DSC. When exposed to a solution of bacterial collagenase, ethylene oxide sterilized materials had a lower rate of degradation compared with nonsterilized DSC. This has been explained by a reduced adsorption of the collagenase onto the collagen matrix as a result of the introduction of pendant N‐2‐hydroxy ethyl groups. © 1995 John Wiley & Sons, Inc.
Bone‐bonding behavior of titanium alloy evaluated mechanically with detaching failure load
Authors: Takatsuka Kazutaka , Yamamuro Takao , Nakamura Takashi , Kokubo Tadashi 
Published: December 2004

AbstractAlthough titanium (Ti) and Ti alloy are generally classified as bioinert materials in terms of their bonding to bone tissue, it is still unclear whether they bond chemically to bone. In this study, we examined the bone‐bonding ability of Ti alloy (Ti‐6Al‐4V) using smooth‐surfaced plates under non‐load‐bearing conditions. The bone‐bonding behavior was evaluated mechanically by means of the detaching test reflecting tensile force. After implantation of the plates into the tibiae of rabbits for 4, 8, 16, and 25 weeks, detaching tests were performed. The failure load of the Ti alloy plates was close to 0 kg at 4 and 8 weeks, but gradually increased with time, reaching 0.334 kg at 16 weeks and 2.852 kg at 25 weeks on average. Histologic examination by Giemsa surface staining and SEM showed no differences between specimens at 8, 16, and 25 weeks, when Ti alloy plate made direct content with bone without any fibrous tissue. By SEM‐EPMA, no clear calcium‐phosphorus (Ca‐P)‐rich layer at the interface between the Ti alloy and bone tissue was evident, although a thin bone tissue was observed on the detached Ti alloy plate. The present results indicate that from both mechanical and histologic viewpoints, Ti alloy bonds directly to bone under static conditions after some time, probably more than 8 weeks. The possibility of chemical bone‐bonding of Ti alloy was suggested. © 1995 John Wiley & Sons, Inc.
Human monocyte/macrophage adhesion and cytokine production on surface‐modified poly(tetrafluoroethylene/hexafluoropropylene) polymers with and without protein preadsorption
Authors: Yun J. K. , DeFife K. , Colton E. , Stack S. , Azeez A. , Cahalan L. , Verhoeven M. , Cahalan P. , Anderson J. M. 
Published: December 2004

AbstractTo study surface property‐dependent human monocyte adhesion and cytokine (IL‐1β, IL‐6, TNF‐α) production, poly(tetrafluoroethylene/hexafluoropropylene) (FEP) polymer was modified to exhibit neutral, anionic, or cationic properties by incorporating amide (CONH2) and/or carboxyl (COOH) or aminoethyl amide [CONH(CH2CH2NH)nCH2CH2NH2] groups on the surface. Monocyte adhesion on surface‐modified FEP polymers and cytokines released by monocytes/macrophages (MC/MO) into the culture medium were compared to control tissue culture polystyrene (TCPS) at days 1 and 8. On day 1, the neutral surface FEP polymer with incorporated amide (NH2) groups showed the greatest inhibition of adhesion, 89% (P ≤ .01), and cytokine production (IL‐1β with 58%, IL‐6 with 70%, and TNF‐α with 39%) compared to control TCPS. In contrast, the highly cationic [CONH(CH2CH2NH)nCH2CH2NH2] surface did not show significant (P > .01) inhibition of monocyte adhesion and cytokine production. When fibrinogen or IgG was preadsorbed to the surface, the inhibitory effects of the neutral surface FEP polymer on monocyte adhesion and cytokine production were not altered. In addition, other surface‐modified FEP polymers showed similar inhibition of monocyte adhesion and cytokine production compared to TCPS. Specifically, as the incorporation of carboxyl (COOH) group content increased on FEP polymer surfaces, monocyte adhesion and cytokine production were also increased on day 1 with IgG preadsorption. On day 8, all surface‐modified FEP polymers showed significant (P < .01) inhibition of monocyte adhesion when fibrinogen or IgG was preadsorbed. However, without protein (fibrinogen or IgG) preadsorption, monocyte adhesion was not significantly inhibited compared to control TCPS. In addition, cytokine production detected by ELISAs on day 8 showed no detectable levels of IL‐1β and significantly decreased levels of IL‐6 compared to day 1 for all tested polymers, with or without protein preadsorpion. Interestingly, the level of TNF‐α production on day 8 remained high although not as high as on day 1. Based on these results, we suggest that FEP polymers with neutral hydrophilic surface properties may adhere and activate the least number of monocytes, which are important mediators of biocompatibility. © 1995 John Wiley & Sons, Inc.
Hydroxyapatite clay for gap filling and adequate bone ingrowth
Authors: Maruyama Masaaki , Terayama Kazuo , Ito Michio , Takei Tsunenori , Kitagawa Eiji 
Published: December 2004

AbstractIn uncemented total hip arthroplasty, a complete filling of the gap between femoral prosthesis and the host bone is difficult and defects would remain, because the anatomy of the reamed intramedullary canal cannot fit the prosthesis. Therefore, it seems practical to fill the gap with a clay containing hydroxyapatite (HA), which has an osteoconductive character. The clay (HA clay) is made by mixing HA granules (size 0.1 mm or more) having a homogeneous pore distribution and a porosity of 35–48 vol%, and a viscous substance such as a saline solution of sodium alginate (SSSA). In the first experiment, the ratio of HA granules and sodium alginate in SSSA is set for the same handling properties of HA clay and polymethylmethacrylate bone cement (standard viscosity) before hardening. As a result, the ratio is set for 55 wt% of HA in the clay and 12.5 wt% of sodium alginate in SSSA (i.e., HA:sodium alginate:saline solution = 9.8:1:7). In the second study, the gap between the femoral stem and bone model is completely filled with HA clay. However, the gap is not filled only with HA granules or HA granules mixed with saline solution. In the third animal experiment, using an unloaded model, histology shows that HA clay has an osteoconductive property bridging the gap between the implant and the cortical bone without any adverse reaction. HA clay is considered a useful biomaterial to fill the gap with adequate bone ingrowth. © 1995 John Wiley & Sons, Inc.