bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interface reactions to PEO/PBT copolymers (polyactive®)after implantation in cortical bone
Authors: Radder A. M. , Leenders H. , van Blitterswijk C. A. 
Published: May 2005

AbstractThe bone reaction at the interface of a range of PEO/PBT copolymers (Polyactive®) after press‐fit implantation in the diaphyseal femur of 20 goats was investigated. The animals were sacrificed at 1, 4, 12, 26, and 52 weeks. Undecalcified histologic sections were prepared, evaluated qualitatively, and quantified with the aid of an image analysis system. The percentage of bone contact was determined morphometrically for all PEO/PBT proportions; for the 70/30 ratio, the percentage of calcification of the material surface and of bonebonding (defined as a continuum at the light microscopic level between calcification within the material surface and bone tissue) were also assessed.PEO/PBT copolymers possess hydrogelic properties, and a direct relation has been established between water‐uptake and PEO content. The swelling behavior of all PEO/PBT substrates resulted in a high degree of bone contact (over 95%) at early stages. From the 12‐week survival time onward the 70/30 revealed higher percentages of bone contact (over 80%) when compared with the other ratios (60/40, 55/45, 40/60, and 30/70). This difference was statistically confirmed 1 year postoperatively. The materials with the higher PEO contents showed the highest amounts of calcification, which is reflected by the rate of bone‐bonding were not observed for 40/60 and 30/70 proportions.The quantitative results confirmed the relation between PEO content, water‐uptake, calcification, and bone‐bonding. It was furthermore demonstrated that PEO/PBT copolymers initially establish a high degree of bone contact, whereas the bone‐bonding properties, especially of the 70/30, accomplish a long‐term implant fixation. © 1994 John Wiley & Sons, Inc.
Application of flow cytometry to determine the cytotoxicity of urethane dimethacrylate in human cells
Authors: Nassiri M. Reza , Hanks Carl T. , Cameron Mark J. , Strawn Susan E. , Craig Robert G. 
Published: May 2005

AbstractThe effects of an oligomer, urethane dimethacrylate (UDMA), on two human cell lines were studied using flow cytometry (FCM). Untreated and treated cultures of propidium iodine‐stained KB (epidermal oral carcinoma cells) and human foreskin fibroblas (HFF) cells were analyzed for cellular DNA content. Concentrations of 10 and 25 μM of UDMA slightly perturbed the KB cell cycle progression at 24 and 48 h of incubation. However, the effect of 50 μ M was more pronounced at the latter incubation time period. In cell growth experiments, the sublethal concentrations (10 and 25 μM) produced inhibition of KB cell growth rate at a moderate level, which resulted in the prolongation of cell population doubling time. Significant inhibition of cell growth occurred when 50 μM (lethal concentration) was used. Data obtained from the cell cycle perturbation analysis, evidenced by FCM, correlated with the extent of inhibition in KB cell growth rates. The effects of sublethal concentrations were reversible during a 24 h period of oligomer withdrawal from culture medium. In contrast, the effects of 50 μM were not reversible. In HFF cells the depletion of S phase in the cell cycle was the major effect of 50 μM of UDMA. It was concluded that FCM technology is an ideal and practical approach for studying the cytotoxicity of components of dental composites. © 1994 John Wiley & Sons, Inc.
Use of diphenylphosphorylazide for cross‐linking collagen‐based biomaterials
Authors: Petite H. , Frei V. , Huc A. , Herbage D. 
Published: May 2005

AbstractCross‐linking of collagen‐based biomaterials increases their strength and persistence in vivo. Recently, we described an efficient cross‐linking process via the formation of acyl azide groups on methylated carboxyl groups of collagen using hydrazine and nitrous acid (referred to here as the hydrazine method). In this report, we propose a simpler, faster way to prepare acyl azide groups and to cross‐link collagen‐based biomaterials, using diphenylphosphorylazide (DPPA) as a reagent. After determining the optimal conditions of cross‐linking with DPPA, we compared the efficiency of this protocol with that using hydrazine and with the classical glutaraldehyde treatment. In order to validate and quantitate the extent of reaction, the degree of crosslinking was determined by the measure of the free primary amino group content of the samples.Treatment of native bovine pericardium with 0.5% DPPA for 24 h led to efficient cross‐linking, corresponding to a 50% decrease in the free primary amino group content of the sample and raising its thermal stability from 62.8 up to 81.3°C. In comparison, the thermal stabilities of glutaraldehydeor hydrazine‐treated pericardium were 85 ± 0.4°C and 83.4 ± 0.1°C. Similar decreases in free primary amino group content and increases in thermal stability were obtained for collagen films treated with DPPA, glutaraldehyde, or hydrazine. These results were corroborated by resistance to bacterial collagenase digestion: DPPA‐treated pericardium had a resistance to collagenase digestion similar to that of glutaraldehyde‐ or hydrazine‐treated pericardium. Residual DPPA content: the concentration of phosphorus in tissue treated with 0.5% DPPA was not significantly different from that of untreated tissue. Treatment by DPPA thus appears to be an efficient, rapid method for cross‐linking collagenbased biomaterials. © 1994 John Wiley & Sons, Inc.
Elutions of metal ions from dental casting alloys and their effect on calcium phosphate precipitation and transformation
Authors: Hidaka S. , Okamoto Y. , Abe K. 
Published: May 2005

AbstractThe elution characteristics of metal ions from dental casting alloys were studied in vitro. Large amounts of nickel (0.12–4.94 mg/cm2) and chromium (<0.01–0.63 mg/cm2) were solubilized from the surface of seven brands of nickel‐chromium alloy in either 1% lactic acid or 0.05% hydrochloric acid solutions. The elution of chromium from two brands of cobalt‐chromium alloys in both eluents was below the detection limit or less than 0.01 mg/cm2. The elution of tin, copper, and zinc from a gold‐palladium‐silver alloy in both eluents was below the detection limit or less than 0.01 and 0.04 mg/cm2. Some amounts of tin (0.19–1.92 mg/cm2) and zinc (0.56–1.73 mg/cm2) were eluted from a silver alloy in both eluents.The effects of five eluting metal ions, i.e., nickel, chromium, tin, copper, and zinc, on the conversion of amorphous calcium phosphate (ACP) to hydroxyapatite (HAP) in vitro also were studied by a pH drop method. All divalent cations except for chromium decreased the rate of HAP transformation and elongated the induction time. Nickel had an inhibitory effect comparable to 1‐hydroxyethylidene‐1, 1‐bisphosphonate (HEBP) on the rate of HAP transformation. Tin, copper, and zinc inhibited similarly, but the inhibition was weaker than that by nickel. Chromium did not inhibit these reactions. © 1994 John Wiley & Sons, Inc.
Blood compatibility of sputter‐deposited alumina films
Authors: Yuhta Toshio , Kikuta Yukiaki , Mitamura Yoshiniori , Nakagane Kenichi , Murabayashi Shun , Nishimura Ikuya 
Published: May 2005

AbstractThe surface modification of metals by the application of blood compatible ceramics is one approach to developing durable and blood‐compatible materials. The blood compatibility of sputter‐deposited alumina films was investigated in vitro. The alumina films were prepared by reactive sputtering and conventional sputtering. Diffractometer studies of the alumina films indicate that the sputter‐deposited alumina films have amorphous structures. Electron spectroscopy chemical analysis studies of the alumina films indicate that the sputter‐deposited alumina films are nonstoichiometric (O/Al ratio of 1.15–1.66).We examined the platelet reaction to the alumina films and the intrinsic coagulation factor XII activation by the alumina films. Medical grade segmented polyurethane was also tested. The alumina films experienced an adhesion of about 50% fewer platelets than the segmented polyurethane. Also, fewer platelet morphologic changes were observed on the alumina films than on the segmented polyurethan. Factor XII activation was less on the alumina films than on the segmented polyurethane. Surface modification by the sputter‐deposited alumina films is promising for developing blood‐compatible and durable materials. © 1994 John Wiley & Sons, Inc.
Hemocompatibility on graft copolymers composed of poly(2‐methacryloyloxyethyl phosphorylcholine) side chain and poly(n‐butyl methacrylate) backbone
Authors: Ishihara Kazuhiko , Tsuji Tsuyoshi , Kurosaki Toshikazu , Nakabayashi Nobuo 
Published: May 2005

AbstractTo improve the hemocompatibility on hydrophobic biomedical materials by a simple coating technique, graft copolymers composed of a hydrophilic side chain with phospholipid polar groups and a hydrophobic backbone were synthesized. The hydrophilic chain had phospholipid polar groups, poly[2‐methacryloyloxyethl phosphorylcholine (MPC)], and the hydrophobic backbone was poly[n‐butyl methacrylate (BMA)]. Because the graft copolymers obtained could dissolve in ethanol, they could be used as a coating material. When the poly(MPC‐graft‐BMA) membrane, the composition of the MPC units on the surface was maintained in the bulk graft copolymer even after immersion in water. Protein adsorption on the membrane coated with the graft copolymer from human plasma detected by a gold‐colloid labeled immunoassay was drastically decreased compared with that on glass and the original membrane. Moreover, blood cell adhesion, activation, and aggregation on the membrane after contact with human citrated whole blood were suppressed by the coating of the graft copolymer. These results clearly show that the poly(MPC‐graft‐BMA) is a suitable material for improving hemocompatibility on the biomedical devices because of its protein adsorption and cell adhesion resistant properties. © 1994 John Wiley & Sons, Inc.
Development of a pericardial acellular matrix biomaterial: Biochemical and mechanical effects of cell extraction
Authors: Courtman David W. , Pereira Christopher A. , Kashef Villa , McComb Donna , Lee J. Michael , Wilson Gregory J. 
Published: May 2005

AbstractThere is evidence to suggest that the cellular components of homografts and bioprosthetic xenografts may contribute to calcification or immunogenic reactions. A fourstep detergent and enzymatic extraction process has been developed to remove cellular components from bovine pericardial tissue. The process results in an acellular matrix material consisting primarily of elastin, insoluble collagen, and tightly bound glycosaminoglycans. Light and electron microscopy confirmed that nearly all cellular constituents are removed without ultrastructural evidence of damage to fibrous components. Collagen denaturation temperatures remained unaltered. Biochemical analysis confirmed the retention of collagen and elastin and some differential extraction of glycosaminoglycans. Low strain rate fracture testing and high strain rate viscoelastic characterization showed that, with the exception of slightly increased stress relaxation, the mechanical properties of the fresh tissue were preserved in the pericardial acellular matrix. Crosslinking of the material in glutaraldehyde or poly(glycidyl ether) produced mechanical changes consistent with the same treatments of fresh tissue. The pericardial acellular matrix is a promising approach to the production of biomaterials for heart valve or cardiovascular patching applications. © 1994 John Wiley & Sons, Inc.
Protein adsorption on low‐temperature isotropic carbon: I. Protein conformational change probed by differential scanning calorimetry
Authors: Feng L. , Andrade J. D. 
Published: May 2005

AbstractThis is the first of a set of articles on protein adsorption on low‐temperature isotropic carbon (LTIC), a reputed blood compatible material. Surface‐induced conformational changes of albumin, fibrinogen, and some small proteins were measured by differential scanning calorimetry (DSC) on LTIC powders and colloidal silica. The LTIC surface significantly alters the DSC response (denaturation?) in proteins studied in different buffer solutions. We use the term „denaturation”︁ to refer to altered protein behavior in the adsorbed state. Hydrophobic interactions between LTIC and the proteins are thought to be the major driving force. The presence of air at the water‐carbon interface seems to prevent the surface denaturation of fibrinogen. The silica surface greatly denatures albumin but only slightly denatures fibrinogen. Because LTIC is considered to be a nonthrombogenic material, but silica is considered to be a thrombogenic one, whether a surface denatures adsorbed proteins cannot be the sole criterion for its blood compatibility. The latter largely depends on what protein the surface denatures, and in what sequences. © 1994 John Wiley & Sons, Inc.
Fibroblast growth on polymer surfaces and biosynthesis of collagen
Authors: Tamada Yasushi , Ikada Yoshito 
Published: May 2005

AbstractThe growth and morphology of rat fibroblasts cultured on various polymer substrates, as well as their collagen biosynthesis, were studied. A clear difference in cell growth and cell morphology was observed among the substrates. The dependence of cell growth on the water contact angle of substrate was similar to that of the adhesion. Fibroblasts could proliferate at the highest rate and showed the highest‐ordered morphology when cultured on the substrate with a contact angle around 70°, which was also the most favorable for cell adhesion. The amount of collagen synthesized by total cells and of adsorption of the synthesized collagen to substrates were in good correlation with the cell growth dependence on the contact angle of substrate, whereas the collagen synthesis per cell was more active on the surfaces poor for cell growth than on the good ones. Cells on surfaces promoting active collagen synthesis had a round shape and clustered upon each other. The collagenimmobilized surface had nearly the highest cell adhesion, high cell proliferation, and high collagen adsorption among the substrates studied. In addition, the highest‐ordered morphology and no lag time for proliferation were observed for the collagen‐immobilized surface. These results indicate that the collagen‐immobilized substrate provides the most favorable surface for cell growth at the initial stage. © 1994 John Wiley & Sons, Inc.
Fracture toughness of single crystal alumina in air and a simulated body environment
Authors: Mitamura Yoshinori , Wang Youfu 
Published: May 2005

AbstractThe critical intensity factor KIC of a single crystal alumina (1100)‐plane in air and in a simulated body environment was measured. Based on these measurements, the estimated durability of a single crystal alumina disk in a ceramic heart valve was determined. Standard single‐edge notched beam specimens were prepared. The specimens were classified into three groups: (a) stored in air (n = 10), (b) immersed in Ringer's solution for 2 months (n = 11), and (c) immersed in Ringer' solution for 4 months (n = 6). KIC was 2.345 ± 0.072 MPam½ for specimens stored in air, 2.141 ± 0.147 in Ringer's solution for 2 months, and 2.005 ± 0.153 in Ringer's solution for 4 months. The KIC decreased for specimens stored in Ringer's solution (P < .01), but it did not differ significantly between 2 and 4 months. The decrease of KIC is the stress corrosion effect of Ringer's solution at the crack tip, and is not associated with an over all deterioration of strength. The stress intensity factor for possible cracks (length: 0.4 mm) in the single crystal alumina was calculated. Maximum stress was assumed 2.668 MPa ( = 40 × 500 mm Hg). The stress intensity factor calculated was far less than the KIC. The single crystal alumina disk can endure a static pressure of 500 mm Hg. © 1994 John Wiley & Sons, Inc.
The acoustic properties of normal and imbedded bovine bone as measured by acoustic microscopy
Authors: Zimmerman Mark C. , Prabhakar Avinash , Chokshi Biren V. , Budhwani Navin , Berndt Hubert 
Published: May 2005

AbstractThe acoustic impedance of bovine femoral cortical bone was measured with a scanning acoustic microscope used in the reflection mode. The bone was measured in the unimbeded state and after plastic imbedding. The acoustic impedance of the unimbedded specimens was also measured with a standard transmission ultrasonic technique. For the unimbedded bovine specimens there was a good correlation between the bulk transmission impedance and the reflection surface impedance (r2 = 0.976) and the values were 9.32 and 9.29 MRayls, respectively. Plastic imbedding produced a consistent and statistically significant increase in the acoustic impedance of the bone (9.71 MRayls). This experiment verified the use of acoustic microscopy as a quantitative materials analysis technique and it demonstrated the potential for material property analysis of imbedded bone. © 1994 John Wiley & Sons, Inc.
Effects of variation of prosthesis size on cement stress at the tip of a femoral implant
Authors: Lee I. Y. , Skinner H. B. , Keyak J. H. 
Published: May 2005

AbstractWith the resurgence of the use of bone cement in total hip arthroplasty, a renewed interest in techniques or designs that may reduce cement fixation failure has arisen. Analysis of the stresses at the tip of the prosthesis may suggest strategies to reduce loosening. This study analyzed stresses in the cement near the tip of a femoral component as a function of cement thickness, using a three‐dimensional finite element model. A section of an idealized circular femoral shaft with implanted prosthesis and cement was modeled with loading conditions representing the stance phase of gait. Increasing cement thickness from 2 to 5 mm by reducing the prosthesis diameter from 15 to 9 mm is predicted to reduce stress significantly in the cement mantle of a femoral implant. Peak tensile stresses are reduced 45%, whereas peak von Mises and shear stresses are reduced 40%. Such a reduction in stress can increase fatigue life by an order of magnitude. Peak interface tensile stresses occur on the medial side at the tip of the prosthesis in a transverse direction, indicating likelihood of failure due to debonding. The shear and tensile stresses predicted by our model greatly exceed the fatigue endurance limit values for both bulk cement and the cement‐prosthesis interface, indicating the likelihood of premature fatigue failure, even allowing for considerable uncertainty. These analytical results suggest that the surgeon should adopt a strategy of selecting a prosthesis that permits a 5‐mm cement mantle near the tip of the prosthesis. © 1994 John Wiley & Sons, Inc.
Antithrombogenicity of lumbrokinase‐immobilized polyurethane
Authors: Ryu Gyu Ha , Park Seonyang , Kim Miran , Han Dong Keun , Kim Young Ha , Min Byounggoo 
Published: May 2005

AbstractLumbrokinase is a potent fibrinolytic enzyme purified from the earthworm, Lumbricus rubellus. We immobilized 18 IU/cm2 of lumbrokinase to polyurethane using maleic anhydride methylvinyl ether copolymer (MAMEC) as an enzyme carrier, and the proteolytic and fibrinolytic activities of immobilized lumbrokinase were assayed. Immobilized lumbrokinase retained about 34% of its activity, compared with soluble lumbrokinase activity. Immobilized lumbrokinase showed stability against thermal inactivation and degradation and within a various pH range. The optimal pH of immobilized lumbrokinase shifted 1.0 pH unit upward compared with soluble enzyme. Upon exposure to the human whole blood, less amount of 125I‐fibrinogen was adsorbed to lumbrokinase‐immobilized surface than to the polyurethane control surface. The lumbrokinase‐immobilized surface showed less platelet adhesion than did the MAMEC‐grafted surface. At the early stage of platelet adhesion, the number of adhered platelets increased on the lumbrokinase‐immobilized surface with increasing time; yet, the platelet number drastically decreased on the lumbrokinase‐immobilized surface after 80 min incubation. This suggests that lumbrokinase‐immobilized polyurethane digested the adsorbed fibrinogen and inhibited platelet adhesion on the surface, probably by inhibiting fibrinogen adsorption to be highly antithrombogenic. Clinical applications of this material to artificial organs should be developed in the near future. © 1994 John Wiley & Sons, Inc.
Developing correlations between fibrinogen adsorption and surface properties using multivariate statistics
Authors: Pérez‐Luna Víctor H. , Horbett Thomas A. , Ratner Buddy D. 
Published: May 2005

AbstractA multivariate model based on the partial least squares algorithm (PLS) was constructed in order to establish a correlation between the surface properties of common polymeric materials and the amount and retention of fibrinogen adsorbed from a complex mixture. Surface characterization was performed by means of static secondary ion mass spectroscopy (SIMS), electron spectroscopy for chemical analysis (ESCA), and by contact angle measurements of several liquids on those materials.125I‐fibrinogen was adsorbed from a 1% plasma solution in buffer and the amount adsorbed after 2 h was determined. After 5 days of residence time in buffer, the adsorbed fibrinogen was eluted with a 1% solution of the surfactant sodium dodecyl sulfate (SDS). The percent of fibrinogen that remained on the surfaces after elution is referred to as fibrinogen retention. Correlations between surface properties and the amounts of fibrinogen adsorbed or fibrinogen retention were established. These models also show the most important variables that are related to the protein behavior on these surfaces. © 1994 John Wiley & Sons, Inc.
Recombinant human bone morphogenetic protein‐2 is superior to demineralized bone matrix in repairing craniotomy defects in rats
Authors: Marden Leslie J. , Hollinger Jeffrey O. , Chaudhari Anshumali , Turek Tom , Schaub Robert G. , Ron Eyal 
Published: May 2005

AbstractThe purpose of this study was to measure bone‐regenerative effects of recombinant human bone morphogenetic protein‐2 (rhBMP‐) in rat calvarial critical‐size defects (CSDs). CSDs (8 mm in diameter) were treated with either: (1) 2.2 µg rhBMP‐ combined with insoluble collagenous bone matrix (ICBM), (2) 6.5 µg rhBMP‐ plus ICBM, (3) ICBM alone, or (4) demineralized bone matrix (DBM), for 7, 14, or 21 days. Multiple linear regression showed that rhBMP‐ had a significant time‐ and dose‐dependent effect on bone regeneration (P < .05). After 7 days, new calcifying cartilage and remineralizing ICBM, with an occasional zone of new woven bone, was evident in defects treated with rhBMP‐/ICBM. By 14 days, both doses of rhBMP‐ reconstituted with ICBM had induced more bone formation than ICBM alone or DBM, and 6.5 µg was superior to 2. 2 m̈g. There was no evidence of adverse cellular response. This study shows for the first time that rhBMP‐ could restore osseous form to a calvarial defect. In addition, osteoregeneration was accelerated by the higher dose of rhBMP‐. © 1994 John Wiley & Sons, Inc.
Thermal stability of sodium hyaluronate in aqueous solution
Authors: Lowry Karen M. , Beavers Ellington M. 
Published: May 2005

AbstractSince its identification 60 years ago as a ubiquitous component of the body of mammals, hyaluronic acid has been widely studied, primarily in the fields of medicine and biology. On the other hand, our research has dealt with hyaluronic acid as a chemical intermediate in the synthesis of novel lubricious coatings, and in this connection data were needed on stability of aqueous solutions of the polymer over a range of temperatures from 25–100°C. The investigation reported here provides that information, obtained by exposing samples in sealed ampules in baths a controlled temperatures and determining the resultin change in viscosity of the solutions. Data of this kind have not previously been reported on sodium hyaluronate free from the proteins and other organics normally associate with the polymer in its natural environment. © 1994 John Wiley & Sons, Inc.