bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of aluminum ions and sorbitol on collagen and skin: A thermally stimulated current spectroscopy study
Authors: Gervais‐Lugan M. , Haran R. , Lamure A. , Lacabanne C.
Published: December 2004

The influence of aluminum ions introduced either directly or with sorbitol, in collagen and skin, has been investigated by Thermally Stimulated Current/TSC spectoscopy. The intramolecular mobility of collagen has been found to be significantly reduced by aluminum ions. The substitution of water molecules by aluminum ions on intramolecular hydrophilic sites is suggested to be responsible for this evolution. The presence of sorbitol minimizes this effect. The intermolecular mobility of collagen is decreased upon introduction of aluminum ions introduction of aluminum ions in presence of sorbitol. This result can be explained by the interaction of sorbitol‐aluminum entities with the telopeptidic regions of collagen molecules. In skin samples, the intra‐ and intermolecular mobilities are restored due to the combined actions of sorbitol and noncollagenous proteins and other macromolecules.
Formation of a multilayer cellular lining on a polyurethane vascular graft following endothelial cell sodding
Authors: Williams Stuart K. , Carter Thomas , Park Pauline K. , Rose Deborah G. , Schneider Timothy , Jarrell Bruce E.
Published: December 2004

Small‐diameter (<6 mm) clinically available vascular grafts often fail due in part to the inherent thrombogenicity of artificial polymers. Transplantation of endothelial cells onto the lumen of these vascular grafts has been suggested as one method to overcome this thrombogenicity. We have developed a compliant polyurethaneurea (PEUU) 4‐mm graft with a luminal surface modified by a glow discharge gas plasma. Autologous microvessel endothelial cells were isolated from canine falciform ligament fat, were transplanted onto the luminal surface of the grafts using an intraoperative isolation and sodding technique, and both endothelial‐cell‐treated and non‐cell‐treated grafts were placed as bilateral carotid interposition grafts in a canine model. After 5 weeks of implantation, explanted control (non‐cell‐treated) grafts exhibited a deposition of platelets, white cells and fibrin characteristic of a thrombogenic surface. MVEC sodded grafts exhibited a multicellular lining within but distinct from the lumen of the PEUU graft. The blood‐contacting surface of this lining exhibited an antithrombogenic endothelial cell monolayer. We suggest that the PEUU graft supported the initial deposition of MVEC and development of an endothelial cell lining. During the 5 weeks of implantation this lining continued to proliferate and detached from the PEUU graft substratum. The final neocellular lining exhibited a luminal diameter and histological features similar to a native artery.
Microhardness measurements of renal calculi: Regional differences and effects of microstructure
Authors: Zhong P. , Chuong C. J. , Goolsby R. D. , Preminger G. M.
Published: December 2004

Microhardnesses of five types of renal calculi: calcium apatite (82.5%)/magnesium ammonium phosphate hydrogen (lo%)/ calcium oxalate monohydrate (7.5%); calcium apatite (95%)/calcium oxalate monohydrate (5%); magnesium ammonium phosphate hydrogen (90%)/calcium apatite (10%); calcium oxalate monohydrate (85%)/calcium apatite (15%); and cystine (100%) were measured. Using Knoop and Vickers indenters the effects of chemical composition and microstructure on the microhardness measurement were assessed. Calcium oxalate monohydrate, magnesium ammonium phosphate hydrogen, and cystine stones, without apparent structure pattern, showed neither regional nor directional differences in their microhardness. In contrast, calcium apatite stones, with distinctly concentric laminae structure, showed regional variations which were correlated with the chemical composition of stone constituents. Scanning electron microscopy of the indenter impressions were taken to help in interpreting the directional dependence in Knoop hardness measurements with respect to the microstructure of the calculi. Vickers measurements showed the crystalline stones were isotropic within a layer. Combined results of Knoop and Vickers measurements indicate that the anisotropic Knoop hardness readings seen in the laminated regions were structural but not material‐based. Implications of the results for the fragmentation of renal calculi in extracorporeal shock wave lithotripsy are discussed. © 1992 John Wiley & Sons, Inc.
Tensile testing of tubular vascular grafts produced by thermal compression fusion of flat collagenous materials
Authors: Wyler A. , Markus R. T.
Published: December 2004

A novel process of fusion bonding for the production of vascular grafts has been investigated. This process, based on the application of pressure and heat in a sophisticated way, has been used for the bonding of the longitudinal edges of flat dermal sheep collagen into tubular forms. The method produces continuous overlapping joints which are expected to overcome the problem of coagulation, as occurs in grafts produced by suturing. The values of the measured shear strength of the bond vary from 750 ± 30 kPa to 940 ± 32 kPa, depending on tube diameter and overlap length (n = 5). These values are much higher than calculated values of the stress in thin‐walled tubes caused by a high static blood pressure, indicating a high safety factor for the fusionbonded vascular grafts. © 1992 John Wiley & Sons, Inc.
Antisera binding onto metals immersed in human plasma in vitro
Authors: Wälivaara Bengt , Askendal Agneta , Elwing Hans , Lundström Ingemar , Tengvall Pentti
Published: December 2004

Titanium (Ti), silicon (Si), silver (Ag), vanadium (V), gold (Au), and chromium (Cr) surfaces were made hydrophilic by radiofrequency plasma treatment. The binding of antifibrinogen (a‐fib) and anti‐high‐molecular‐weight kininogen (a‐HMWK) after incubation of surfaces in 10% human blood plasma was investigated with ellipsometry. Ti and Si surfaces bound a‐HMWK but no detectable amounts of a‐fib, whereas the other metals bound both types of antisera. Protein adsorption in a fluid gradient produced under a convex lens indicated that the small deposition of a‐fib on Ti and Si surfaces is probably a result of protein displacement. This displacement was not evident a t lens positions simulating low plasma concentrations where large amounts of a‐fib adsorbed. Surfaces washed sequentially in trichloroethane, acetone, and ethanol produced more hydrophobic surfaces and resulted in slower rates of a‐fib displacement. These studies would indicate that some metals form complexes with specific plasma proteins or, alternatively, that different metals may bind equal amounts of plasma proteins which express differing antigenicities to‐ward their surroundings. © 1992 John Wiley & Sons, Inc.
Decreased tissue reaction to bioprosthetic heart valve material after L‐glutamic acid treatment. A morphological study
Authors: Grabenwöger Martin , Grimm Michael , Eybl Elisabeth , Leukauf Christian , Müller Mathias M. , Plenck Hanns , Böck Peter
Published: December 2004

Degenerative alterations of two different glutaraldehyde (GA)‐fixed bioprosthetic heart valve materials were investigated in subcutaneous rat implants: Bovine pericardium, prepared according to clinically used bioprosthetic heart valve material (BHV) was compared to alternatively preserved pericardium (APHV), which was fixed in GA and treated with L‐glutamic acid. Following 63 days of subcutaneous implantation, calcification of APHV implants was significantly lower as compared to BHV implants (13 ± 6 versus 158 ± 18 μg Ca/mg dry weight tissue; p ± 0.05). In BHV implants ultrastructural investigations showed nucleation of plate‐shaped hydroxyapatite crystals at the surface of collagen fibrils and in remnants of connective tissue cells; no signs of calcification could be detected in APHV implants. The time‐course of the inflammatory reaction was determined by quantification of immunohistochemical stained mononuclear host‐cells invading the implants. In both preparation groups inflammatory reaction reached maximum 42 days after implantation. However, infiltration rate of inflammatory cells was markedly decreased in APHVs as compared to BHVs (p ≤ 0.05). © 1992 John Wiley & Sons, Inc.
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

A 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

To 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

Studies 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

It 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

The 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

Small‐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

Polymers 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

The 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

The 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

Porous 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

The 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

Although 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

To 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

In 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.
Adhesion and cytokine production by monocytes on poly(2‐methacryloyloxyethyl phosphorylcholine‐co‐alkyl methacrylate)‐coated polymers
Authors: Defife K. M. , Yun J. K. , Azeez A. , Stack S. , Ishihara K. , Nakabayashi N. , Colton E. , Anderson J. M.
Published: December 2004

Human monocytes isolated from peripheral venous blood were assayed for their ability to adhere to various polymers. The culture supernatants were also assayed for the cytokines, interleukin‐1β (IL‐1β), interleukin‐6 (IL‐6), and tumor necrosis factor‐α (TNF‐α). The polymers evaluated for adherence and cytokine production included Pellethane®, polyethylene and poly[n‐butyl methacrylate (BMA)] coated with poly[2‐methacryloyloxyethyl phosphorylcholine (MPC)‐co‐alkyl methacrylate] copolymers. In some experiments the test polymers were adsorbed with fibrinogen or IgG prior to the addition of monocytes. MPC copolymer‐coated materials inhibited monocyte and macrophage adhesion after 1 and 8 days of culture relative to corresponding uncoated polymers and tissue culture polystyrene (TCPS). The degree of inhibition by coated Pellethane compared to uncoated Pellethane was the greatest, while inhibition of adhesion by coated poly(BMA) was the least compared to uncoated poly(BMA). However, adhesion was significantly decreased on both coated and uncoated poly(BMA) by day 8. While IL‐1β, IL‐6, and TNF‐α release was variably influenced by polymer coating, release was consitently inhibited relative to TCPS on day 1. However, cytokine production was not inhibited compared to corresponding uncoated polymers on day 1. With or without protein preadsorption, IL‐1β release was not detectable in the supernatants of any polymer on day 8, IL‐6 production was diminished on day 8, and TNF‐α production was sustained on day 8. Overall, MPC copolymercoated and uncoated poly(BMA) were the least stimulating, while TCPS was the most stimulating. These studies suggest that MPC copolymers may improve the cell adhesion‐resistant properties of a biomaterial while variably influencing the activation of cells which may contact the coated surface. © 1995 John Wiley & Sons, Inc.
Effect of carbon content on the resistance to localized corrosion of as‐cast cobalt‐based alloys in an aqueous chloride solution
Authors: Montero‐Ocampo C. , Salinas Rodriguez A.
Published: December 2004

The effect of carbon content on the resistance to localized corrosion of ASTM‐F75, as‐cast cobalt‐based alloys, was studied using potentiostatic polarization tests in Ringer's solution. Critical pitting potentials were estimated from the potentiostatic polarization curves and were found to increase with decreasing carbon content. The highest resistance to pitting corrosion observed at low C contents was attributed to a greater chemical and microstructural homogeneity in the as‐cast condition. The results of the investigation led to the conclusion that the use of low C content ASTM‐F75 as‐cast alloys in the manufacture of orthopedic implants may result in a lower release rate of corrosion products which should improve the “in vivo” performance of the implants. © 1995 John Wiley & Sons, Inc.
Bacteria/blood/material interactions. I. Injected and preseeded slime‐forming Staphylococcus epidermidis in flowing blood with biomaterials
Authors: Brunstedt M. R. , Sapatnekar S. , Rubin K. R. , Kieswetter K. M. , Ziats N. P. , Merritt K. , Anderson J. M.
Published: December 2004

Blood‐material interactions were studied using in vitro recirculation with human blood, slime‐forming Staphylococcus epidermidis, and cardiovascular materials. Staphylococcus epidermidis, under preseeded or injected conditions, adhered to nonsmooth materials and elevated plasma levels of fibrinopeptide A (FpA) and C3a in the presence of all materials. Increased white blood cell (WBC) and platelet adhesion and thrombospondin and platelet factor 4 (PF4) release were noted for respective materials in the presence of injected bacteria. Materials that adhered significant quantities of injected S. epidermidis exhibited low levels of adsorbed proteins. Materials with high levels of preseeded S. epidermidis showed high levels of adsorbed proteins. Adhesion of preseeded bacteria and blood plasma elevations of C3a and FpA were lowest on semicrystalline polymer substrates, intermediate on halogenated substrates, and highest on amorphous substrates. In the presence of injected bacteria, WBCs and platelets adhered at earlier recirculation times to amorphous substrates than to semicrystalline substrates. © 1995 John Wiley & Sons, Inc.
Hydrogel‐based three‐dimensional matrix for neural cells
Authors: Bellamkonda Ravi , Ranieri John P. , Bouche Nicolas , Aebischer Patrick
Published: December 2004

The ability to organize cells in three dimensions (3D) is an important component of tissue engineering. This study sought to develop an extracellular matrix (ECM) equivalent with a physicochemical structure capable of supporting neurite extension from primary neural cells in 3D. Rat embryonic day 14 striatal cells and chick embryonic day 9 dorsal root ganglia extended neurites in 3D in agarose hydrogels in a gel concentration‐dependent manner. Primary neural cells did not extend neurites above a threshold agarose gel concentration of 1.25% wt/vol. Gel characterization by hydraulic permeability studies revealed that the average pore radius of a 1.25% agarose gel was 150 mm. Hydraulic permeability studies for calculating average gel pore radius and gel morphology studies by environmental and scanning electron micrography showed that the average agarose gel pore size decreased exponentially as the gel concentration increased. It is hypothesized that the average gel porosity plays an important role in determining the ability of agarose gels to support neurite extension. Lamination of alternating nonpermissive, permissive, and nonpermissive gel layers facilitated the creation of 3D neural tracts in vitro. This ability of agarose hydrogels to organize, support, and direct neurite extension from neural cells may be useful for applications such as 3D neural cell culture and nerve regeneration. Agarose hydrogel substrates also offer the possibility of manipulating cells in 3D, and may be used as 3D templates for tissue engineering efforts in vitro and in vivo.
Microstructural investigation of bone—cement interface
Authors: Savarino L. , Stea S. , Ciapetti G. , Paganetto G. , Donati M. E. , Alvergna P. , Pizzoferrato A.
Published: December 2004

We evaluated the microstructural characteristics of newly formed bone tissue at the interface with cement. The bone‐cement interfaces of the femoral components of nine hip prostheses retrieved after loosening were investigated by means of X‐ray diffraction on microareas and microhardness. The bone far from the interface of two stable prostheses was used as a control. The newly formed bone adjacent to cement in the loosened prostheses showed a maturity degree lower than that of bone adjacent to cement in stable prostheses. The lattice parameters of bone apatite did not show significant variations as compared to the reference values. Bone trabeculae at the interface with loosened prostheses often showed an osteoid lining characterized by a strongly demineralized lamellar and haversian structure. Radioopaque cement particles are sometimes found in the trabecular bone tissue around the prosthesis. © 1995 John Wiley & Sons, Inc.
Monosize poly(ethylcyanoacrylate) microspheres: Preparation and degradation properties
Authors: Tuncel A. , Çiçek H. , Hayran M. , Pişkin E.
Published: December 2004

Monosize, biodegradable poly(ethylcyanoacrylate) (PECA) microspheres in the size range of 0.5–2.5 μm were prepared by a relatively new polymerization technique, the so‐called dispersion polymerization. The polymerizations were performed by using a stabilizer system containing a poly(ethyleneoxide)/poly(propyleneoxide) (PEO/PPO) copolymer and dextran in the aqueous HCl solution as a dispersion medium. Phosphoric acid was used as a catalyst, stabilizer, monomer concentrations, and the pH of dispersion medium on the monomer conversion, average size, and size distribution of the PECA microspheres were studied. The resultant microspheres size was mainly controlled by PEO/PPO copolymer and HCl concentrations. To explain the degradation mechanism, the degradation of monosize PECA microspheres was studied in in vitro conditions. The partially degraded beads were observed by electron microscopy. The results indicated that the degradation of monosize PECA microspheres occurred mainly by surface erosion. © 1995 John Wiley & Sons, Inc.
Platelet and monoclonal antibody binding to fibrinogen adsorbed on glow‐discharge‐deposited polymers
Authors: Kiaei David , Hoffman Allan S. , Horbett Thomas A. , Lew Ken R.
Published: December 2004

The state of fibrinogen adsorbed on untreated and glow‐discharge‐treated surfaces was examined by measuring platelet adhesion, monoclonal antibody (mAb) binding, the amount of fibrinogen adsorbed, and the amount of adsorbed fibrinogen which could be eluted with sodium dodecyl sulfate (SDS). Tetrafluoroethylene (TFE) glow‐discharge‐treated polymers have a lower surface free energy (in air) and retain a larger fraction of adsorbed fibrinogen than untreated surfaces after SDS elution. Platelet adhesion was lowest on the TFE‐treated surfaces which retain the highest amounts of fibrinogen after SDS elution. Fibrinogen may undergo unfolding or spreading on the TFE‐treated surfaces to minimize interfacial free energy (in water) and maximize protein–;surface interactions. When it is adsorbed on the TFE‐treated surfaces, fibrinogen evidently assumes a state which somehow prevents its recognition and binding by platelet receptors. Monoclonal antibodies that bind to the three regions in fibrinogen thought to be involved in platelet adhesion were therefore used to detect changes in adsorbed fibrinogen. These regions and the antibodies which bind to them are: the COOH‐terminal of the γ‐chain, mAb M1; the RGD peptide sequence at Aα 95–98, mAb R1; the RDG sequence at Aα 572–575, mAb R2. For fibrinogen adsorbed on the untreated or TFE‐treated surfaces, M1 and R2 binding was relatively high compared to background, while R1 binding was low. However, the amount of binding of each mAb to fibrinogen adsorbed on the TFE‐treated surfaces was equal to or greater than fibrinogen adsorbed to the untreated surfaces. Therefore, antibody‐detectable changes in the platelet binding regions of adsorbed fibrinogen that might have been caused by conformational or orientational rearrangements were not observed for the TFE‐treated surfaces. The data suggest that the tight binding of fibrinogen on a surface may directly affect the ability of the fibrinogen to interact with the platelet receptors—i.e., that fibrinogen must be loosely held to facilitate maximal interaction with platelet receptors. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of fluoropolymeric substrata with immobilized minimal peptide sequences for cell adhesion studies. I
Authors: Vargo T. G. , Bekos E. J. , Kim Y. S. , Ranieri J. P. , Bellamkonda R. , Aebischer P. , Margevich D. E. , Thompson P. M. , Bright F. V. , Gardella J. A.
Published: December 2004

In this work, poly(tetrafluoroethylene‐cosubstrathexafluoropropylene) (also known as fluorinated ethylene propylene; FEP) was functionalized at the surface using a radio frequency glow discharge plasma. This particular surface modification produced controlled densities of hydroxyl functionality on the FEP surface. These surface hydroxyl groups provided sites for the covalent attachment of minimal peptide sequences, that are specific for neuronal attachment. FSCA, ATR‐FTIR, ToFsubstratSIMS, and fluorescence spectroscopy were used to evaluate peptide reaction efficiencies and to verify that intact peptide sequences were covalently attached to the FEP surfaces. These modified substrata were then used to study the cell attachment and response to covalently bound minimal peptide sequences. Cell attachment and differentiation results using NG108–15 and PC12 neuronal cell lines are presented in the adjoining paper by Ranieri et al. © 1995 John Wiley & Sons, Inc.
Neuronal cell attachment to fluorinated ethylene propylene films with covalently immobilized laminin oligopeptides YIGSR and IKVAV. II
Authors: Ranieri John P. , Bellamkonda Ravi , Bekos Evan J. , Vargo Terrence G. , Gardella Joseph A. , Aebischer Patrick
Published: December 2004

Material surfaces that can mediate cellular interactions by the coupling of specific cell membrane receptors may allow for the design of a biomaterial that can control cell attachment, differentiation, and tissue organization. Cell adhesion proteins have been shown to contain minimum oligopeptide sequences that are recognized by cell surface receptors and can be covalently immobilized on material surfaces. In this study, cell attachment to fluorinated ethylene propylene (FEP) films functionalized with the laminin‐derived oligopeptides, YIGSR and a 19‐mer IKVAV‐containing sequence, was assessed using NG108–15 neuroblastoma and PC12 cells. A radiofrequency glow discharge (RFGD) process that replaces the FEP surface fluorine atoms with reactive hydroxyl functionalities was used to activate the film surfaces. The oligopeptides were then covalently coupled to the surface by their C‐terminus using a standard nucleophilic substitution reaction. The covalent attachment of the oligopeptides to the FEP surface was verified using electron spectroscopy for chemical analysis (ESCA). Receptor‐mediated NG108–15 cell attachment on the YIGSR‐modified films was determined using competitive binding assays. Average cell attachment on the oligopeptide immobilized films in medium containing soluble CDPGYIGSR was reduced by approximately a factor of 2, compared to cell attachment in serum‐free medium alone. No significant decrease in cell attachment was noted in medium containing the mock oligopeptide sequence CDPGYIGSK. FEP films immobilized with the 19‐mer IKVAV sequence demonstrated a higher percentage of receptor mediated cell attachment on the film surfaces. A sixfold decrease in PC12 cell attachment occurred on the oligopeptide immobilized films in a competitive binding assay medium containing the soluble IKVAV oligopeptide compared to cell attachment in serum‐free medium alone. These results demonstrate that laminin oligopeptides can be covalently immobilized on an FEP material surface and analytically verified, and can mediate the receptor specific coupling of neuronal cells onto its surface. © 1995 John Wiley & Sons, Inc.
Contact activation of the plasma coagulation cascade. II. Protein adsorption to procoagulant surfaces
Authors: Vogler Erwin A. , Graper Jane C. , Sugg Harry W. , Lander Lorraine M. , Brittain William J.
Published: December 2004

A study of blood protein adsorption to procoagulant surfaces utilizing a coagulation time assay, contact angles, Wilhelmy balance tensiometry, and electron spectroscopy (ESCA) is presented. Using a new contact angle method of measuring protein adsorption termed “adsorption mapping” it was demonstrated that protein‐adsorbent surfaces were inefficient activators of the intrinsic pathway of the plasma coagulation cascade whereas water‐wettable, protein‐repellent surfaces were efficient procoagulants. Repeated use of fully water‐wettable (spreading) glass procoagulants in the coagulation time assay demonstrated that putative “activating sites” were not consumed in the coagulation of platelet‐poor porcine plasma. Furthermore, these procoagulant surfaces retained water‐wettable surface properties after incubation with blood proteins and saline rinse. The interpretation of these observations was that plasma and serum proteins were not adsorbed to water‐wettable surfaces. However, ESCA of these same surfaces revealed the presence of a thin protein layer. Wilhelmy balance tensiometry resolved these seemingly divergent observations by demonstrating that protein was “associated” with a bound hydration layer, but not formally adsorbed through a surface dehydration or ionic interaction mechanism. © 1995 John Wiley & Sons, Inc.
Assessments of thrombogenicity by three in vitro techniques
Authors: Skarada Douglas J. , Erickson Geoffrey R. , Warnecke Kindra L. , du Laney Tracey V. , Greenberg Charles S. , Ritter Edmond F. , Klitzman Bruce
Published: December 2004

This study assessed three in vitro techniques designed to measure the thrombogenicity of vascular grafts. All techniques immersed vascular grafts in rotating blood. In the gravimetric analysis, the weight of adherent thrombi was recorded at 2 min intervals for 20 min. In the torque analysis, a microviscometer continuously recorded the amount of torque developed as the graft rotated for 20 min. In the thrombin analysis, the blood sample was analyzed for fibrinopeptide A production indicating fibrinogen clevage. Expanded polytetrafluoroethylene grafts were treated by removal of air nuclei (denucleation), binding of heparin, or binding of polyethylene oxide (PEO). The gravimetric analysis determined that the time at which each group experienced clot initiation was as follows: control after 6 min, denucleation after 14 min, heparin after 18 min, and PEO after 10 min. Similarly, in the torque analysis all treatment groups significantly delayed the initial increase in torque from 8.0 min for control to 12.5 min for denucleation (P < .01), > 20 min for heparin (P < 0.1), and 12 min for PEO (P < .05). The thrombin analysis determined that coagulation activity was reduced relative to control at 12 min with the denucleation group (P < .05) and heparin group (P < .01) and at 18 min with all treatment groups (P < .01). The similarity of results among the techniques increases confidence that each measurement accurately predicts in vitro thrombogenicity. © 1995 John Wiley & Sons, Inc.