bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface field of forces and protein adsorption behavior of poly(hydroxyethylmethacrylate) films deposited from plasma
Authors: Morra M. , Cassinelli C. 
Published: May 2005

AbstractPolymeric films were deposited from hydroxyethylmethacrylate (HEMA) plasma on non‐woven poly(butyleneterephtalate) (PBT) filter materials. To test the effect of deposition conditions on surface properties, film were deposited using a constant monomer flow rate and a discharge power ranging from 40–100 W. Surface composition and surface energetics were evaluated by Electron Spectroscopy for Chemical Analysis (ESCA) and contact angle measurement, respectively. Albumin (Alb) and fibrinogen (Fg) adsorption from single protein solution to the plasmacoated filters was measured. Results illustrate the marked effects of the deposition conditions on the surface composition, the surface field of forces, and the protein adsorption behavior. The latter is modeled by the application of the Good‐van Oss‐Chaudhury theory of Lewis acid‐base contribution to interfacial energetics. Materials endowed with widely different properties are obtained from the same monomer and different deposition conditions, a result that must be taken into account both in the production step, to assure constant quality, and in the development of specifically tailored materials. © 1995 John Wiley & Sons, Inc.
Zeta potential of bone from particle electrophoresis: Solution composition and kinetic effects
Authors: Kowalchuk Roman M. , Pollack Solomon R. , Corcoran Thomas A. 
Published: May 2005

AbstractThe morphology of bone may be influenced by many factors, including electromechanical ones such as electric potentials, electric fields, or zeta potentials. Stress‐generated potential studies in bone and particle electrophoresis studies using calcium‐deficient hydroxyapatite have shown that the zeta potential depends on the composition of the steeping fluid and steeping time. To better quantify and understand these in situ potential changes in bovine cortical bone, the effects of alterations in calcium, phosphate, and fluoride concentrations in Neuman's Fluid (NF), which simulates in vivo bone extracellular fluid, were investigated using particle electrophoresis. The zeta potential increased in magnitude with increased calcium concentration in NF in as little as 17 min. Increasing phosphate concentration in NF also increased the zeta potential magnitude. These results provide support for a structural model of the bone matrix surface‐bone fluid interface, which incorporates the bone surface proper (composed of collagen, mineral, and boundary regions), stationary layer (in which ions, ionic complexes, and proteins may be adsorbed), and bone extracellular fluid. These results, coupled with those of previous studies, indicate that the protein phase probably has an important role in the determination of the physiologic zeta potential; the role of the mineral phase may also be important. © 1995 John Wiley & Sons, Inc.
Studies on the tumor‐promoting activity of biomaterials: Inhibition of metabolic cooperation by polyetherurethane and silicone
Authors: Tsuchiya Toshie , Hata Hideyo , Nakamura Akitada 
Published: May 2005

AbstractWhen V79 metabolic cooperation (MC) assay was performed to detect tumor‐promoting activities, inhibitory activities on the gap‐junctional intercellular communication were first detected in both extracts prepared from polyetherurethane (PEU) and silicone. The former inhibited more strongly than the latter. Furthermore, the lowest effective concentrations in MC assay correlated well with the values of the total active incidences obtained by histologic evaluation of the 2‐year implantation test in rats. Poly(tetramethylene oxide) (PTMO) showed the highest inhibitory activities among the constituents of PU. Thus, the shorter the chain length of PTMO, the stronger the inhibitory activities of PTMO in MC assay. PTMO moiety may play an important role in the tumor‐promotion stage during tumorigenesis induced by PU. © 1995 John Wiley & Sons, Inc.
Formation and properties of a synthetic bone composite: Hydroxyapatite–collagen
Authors: TenHuisen Kevor S. , Martin Roger I. , Klimkiewicz Maria , Brown Paul W. 
Published: May 2005

AbstractComposites composed of microcrystalline calcium‐deficient hydroxyapatite (HAp) and collagen were formed at 38°C via an acid‐base reaction between calcium phosphate precursors in the presence of a collagen matrix. Formation of composites having HAp:collagen weight ratios of 4.5:1, 11:1, and 22:1, along with that of pure mineral were investigated. Isothermal calorimetry and X‐ray diffraction indicated complete reaction within 5 h resulting in hardened monoliths. The rate of HAp formation increased with an increase in the proportion of collagen present. Electron microscopy indicated that the acceleratory effect of collagen was associated with the provision of nucleation sites for HAp crystallization. Analysis of the solution chemistry also showed that collagen affected the calcium and phosphate concentrations and the pH. While collagen was shown to effect the kinetics of HAp formation, the rate limiting step, as shown by X‐ray diffraction and solution chemistry, was the dissolution of the acidic calcium phosphate precursor, CaHPO4. Preliminary mechanical data indicated that the Young's modulus, yield strength, and work to fracture were at the lower end of the range of those values reported for bone. The porosities observed in these composites suggest that they might be osteoinductive while their compositions should allow their eventual resorption. Thus, microstructure, kinetics, and mechanical data suggest that these composites might be suitable as bone substitutes which form in vivo. © 1995 John Wiley & Sons, Inc.
Heparin release from thermosensitive polymer coatings: in vivo studies
Authors: Gutowska Anna , Bae You Han , Jacobs Harvey , Mohammad Fazal , Mix Donald , Feijen Jan , Kim Sung Wan 
Published: May 2005

AbstractBiomer/poly(N‐isopropylacrylamide)/[poly(NiPAAm)] thermosensitive polymer blends were prepared and their application as heparin‐releasing polymer coatings for the prevention of surface‐induced thrombosis was examined. The advantage of using poly(NiPAAm)‐based coatings as heparin‐releasing polymers is based of the unique temperature‐dependent swelling of these materials. At room temperature, i.e., below the lower critical solution temperature (LCST) of poly(NiPAAm), the Biomer/(poly(NiPAAm)) coatings are highly swollen. The high swelling enables fast loading of hydrophilic macromolecules (e.g., heparin) into the coating by a solutions sorption technique. At a body temperature, i.e., above the LCST of poly(NiPAAm) the coatings are in a deswollen state and the absorbed macromolecules may be slowly released from a dense coating via a diffusion controlled mechanism. Biomer/poly(NiPAAm)) coatings were obtained by blending and coprecipitation of the two linear polymers, Biomer and (poly(NiPAAm). The structure and water‐swelling properties of the coatings were examined. Significant differences in water swelling at room temperature (RT) and 37°C were observed as a result of the thermosensitivity of poly(NiPAAm). The surface structure of the coatings in dry and swollen states at RT and 37°C was examined by scanning electron microscopy. Heparin was loaded into the coatings via a solution sorption at room temperature. Kinetic studies of heparin loading demonstrated that maximum loading was obtained within 1 h. The in vitro (37°C) release profiles were characterized by a rapid initial release due to the squeezing effect of the collapsing polymer network, followed by a slower release phase controlled by heparin diffusion through the dense coating. The short‐term antithrombogenicity of intravenous polyurethane catheters coated with heparin‐releasing Biomer/poly(NiPAAm) thermosensitive coating was evaluated in a canine animal model. The results show that the heparin release from Biomer/poly(NiPAAm)‐coated surfaces resulted in a significant reduction of thrombus formation on test surfaces in contact with venous blood as compared to control surfaces. © 1995 John Wiley & Sons, Inc.
Interspecies variation of compressive biomechanical properties of the meniscus
Authors: Joshi Meena D. , Suh Jun‐Kyo , Marui Takashi , Woo Savio L.‐Y. 
Published: May 2005

AbstractVarious animal models have been used to investigate the normal and reparative properties of the knee meniscus. Yet, only limited data on meniscal biomechanical properties of various animals are available. It was therefore the objective of this study to compare measurements of meniscal biomechanical properties between six species: human, bovine, monkey, canine, sheep, and porcine. Uniaxial confined compression tests were conducted on 1‐mm‐thick, 4‐mm‐diameter meniscal discs, and the viscoelastic creep deformation was obtained. Two biomechanical parameters, the aggregate modulus (HA) and permeability (κ), were found by implementing the linear biphasic theory and a newly developed nonlinear regression scheme. A one‐way analysis of variance was conducted along with Student‐Newman‐Keuls comparison tests to assess the differences in these parameters among the species. Sheep menisci exhibited HA and κ values most similar to human menisci. The water content of each specimen was also measured and correlated significantly with κ. The interspecies variations found in material properties of the knee meniscus indicate the need for caution in extrapolating data on the biomechanical behavior of the human meniscus from animal models. © 1995 John Wiley & Sons, Inc.
Viscoelastic and adherence properties of dental relining materials
Authors: Buch D. , Wehbi D. , Roques‐Carmes C. 
Published: May 2005

AbstractThe viscoelastic properties of three classes of soft relining materials (acrylic resins, silicones, and EVA copolymers) were studied comparatively. Their behaviors were investigated by in vitro tests at a frequency ω = 1 Hz, which simulates the masticatory cycle. The experimental parameter was the temperature (T). Black graphs giving the variations of the stiffness K—proportional to the complex viscoelastic modulus E*(T)ω—according to the phase angle δ, were used for a predictive approach to increase the comfort of removable dentures. Cole–Cole diagrams, describing the variation of the loss modulus E″(T)ω in relation to the storage modulus E′(T)ω additionally provide quantitative data. The values obtained were related to the noninteger parameter h used for modelization of the viscoelastic behavior of the materials by means of nonlinear Zener models. An attempt was made to correlate the experimental data to the viscoelastic energy loss observed when instability of the prosthetic structure occurs. This attempt takes into account the formation of “cracks” (areas of inadaptation) between the prosthetic intrados and the mucosa. © 1995 John Wiley & Sons, Inc.
Water transport in dehydrating hydrogel contact lenses: Implications for corneal desiccation
Authors: Martin Donald K. 
Published: May 2005

AbstractThis article provides direct evidence that the rate of evaporation from the anterior surface of a hydrogel contact lens is related to the bulk water transport within the contact lens, analogous to diffusion‐controlled evaporation. The evaporative flux of water from the anterior surface of a contact lens, with free access to water at its posterior surface, was greater for contact lenses of greater overall water content. Blockage of the water entry to the posterior surface of the contact lens reduced the evaporative loss from the anterior surface by 44%. These results suggested that a decrease in the rate of lens bulk water transport during wear would lead to a reduced evaporation rate from the anterior lens surface, for example, if the contact lens water content was reduced due to lipid and mucus adsorption. In addition, a rise in the external temperature of 1.3° was required to produce a significant increase (2 SD) in the evaporative flux from the contact lenses. This suggests that the steadystate water content in vivo may not be significantly influenced by temperature cycling during blinking. © 1995 John Wiley & Sons, Inc.
Surface microarchitectural design in biomedical applications: Preparation of microporous polymer surfaces by an excimer laser ablation technique
Authors: Nakayama Yasuhide , Matsuda Takehisa 
Published: May 2005

AbstractIn this report we demonstrate a microprocessing method to prepare microporous polymer films by an excimer laser ablation technique, which may enable the fabrication of functional biomedical devices such as advanced artificial organs. The irradiation of a KrF excimer laser pulses (wavelength 248 nm; fluence 1 J/cm2 pulse) onto several polymer films was achieved by passing a laser pulse through an optical microscope, resulting in the formation of an etched pit on the irradiated surface due to ablative photodecomposition. The number of pulses and the micropositioning of the irradiation were precisely controlled by a computeraided control unit. Minimal ablation was observed for polyethylene with very small absorption coefficient (α) at 248 nm. For polymers which absorbed the laser photons, the etch depth increased linearly with number of pulses. The etch depth per pulse decreased with an increase in α values. An excellent structural quality, with micron‐order precision of an etched pit, was found for those polymers with larger α a values, such as polyimide, segmented polyurethane, and polycarbonate. © 1995 John Wiley & Sons, Inc.
Contact activation during incubation of five different polyurethanes or glass in plasma
Authors: van der Kamp K. W. H. J. , Hauch K. D. , Feijen J. , Horbett T. A. 
Published: May 2005

AbstractDuring blood‐material interaction, the enzymes factor XII fragment (factor XIIf) and kallikrein are generated (contact activation). In this study, the enzymatic activities of factor XIIf and kallikrein were examined with an assay based on the conversion of tripeptide‐p‐nitroanilide substrate. With the use of aprotinin to inhibit kallikrein, the proteolytic activities of factor XIIf and kallikrein could be separately determined. In this in vitro study, two commercially available polyurethanes, Pellethane and Biomer®; three custom synthesized polyurethanes; a biomerlike 2000 Mw polytetramethyleneoxide containing polyurethane (PU‐2000); an octadecyl extended (ODCE) biomer‐like 2000 Mw Polytetramethyleneoxide containing polyurethane (PU‐2000‐ODCE); a hard‐segment polyurethane (HS‐PU); and glass (reference material) were incubated in 25% diluted plasma. In both series of experiments, glass caused the highest amidolytic activities by factor XIIf and kallikrein compared with any of the polyurethanes. In contrast, within the polyurethane group of materials, lower amidolytic activities by factor XIIf and kallikrein were measured on the custom‐made polyurethanes than on the commercially available polyurethanes, although the differences among the polyurethanes were small. In addition, the influence of different ratios of material surface to the plasma incubation volume was studied. An increased ratio of surface area over plasma volume resulted in reduced contact activation, suggesting that plasma components are the limiting factor. © 1995 John Wiley & Sons, Inc.
Effect of annealing temperature on the degradation of reinforcing fibers for absorbable implants
Authors: Choueka Jack , Charvet Jose Luis , Alexander Harold , Oh Young H. , Joseph Gary , Blumenthal Norman C. , LaCourse William C. 
Published: May 2005

AbstractCalcium phosphate fibers designed for reinforcement of bioabsorbable fracture fixation devices were evaluated for their properties upon annealing. The composition of these fibers were 54% PO4, 27% Ca, 12% ZnO, 2.5% NaPO3, and 4.5% Fe2O3, and they were either not annealed, annealed at 250°C, or annealed at 420°C. Chemical degradation, mass loss, and morphology upon degradation were studied. Chemical degradation was performed in Tris‐buffered HCl, while mass loss and morphologic studies were performed in both physiologic and nonphysiologic solutions. The results showed that degradation rates for fibers were inversely proportional to the annealing temperature. Mass loss analysis of fibers immersed in the two physiologic solutions (calf serum and simulated body fluid) revealed little change in fiber diameter up to 60 days. Morphologic examination revealed little change in fibers immersed in the two physiologic solutions until 60 days, after which thin shells were found to be peeling off the outer coating of the fiber. Samples in tris‐buffered HCl revealed a dramatic difference in mode of degradation among the three fibers. Fibers not annealed and those annealed at lower temperatures underwent a delaminating type of degradation that appeared to destroy the overall integrity of the fiber, whereas fibers annealed at 420°C underwent crater‐like deterioration in which the overall alignment of the fiber remained intact. It is therefore concluded that annealing fibers at higher temperatures slows degradation. The fibers annealed at the highest temperatures also undergo a mode of degradation that allows them to maintain their structural integrity. Although annealing of fibers close to glass transition temperature may produce an initially weaker fiber, chemical and physical degradation occur much slower, making these fibers most suitable for reinforcement of biodegradable implants. © 1995 John Wiley & Sons, Inc.
Preparation of a macroporous biodegradable polylactide implant for neuronal transplantation
Authors: Schugens Ch. , Grandfils Ch. , Jerome R. , Teyssie Ph. , Delree P. , Martin D. , Malgrange B. , Moonen G. 
Published: May 2005

AbstractThis article reports the production of a surgical implant meeting several specific requirements such as biocompatibility, biodegradability, macroporosity, and flexibility. Porosity was controlled by an original method consisting of the aggregation of calibrated poly‐D,L‐lactide microparticles. The size of the interstices between the aggregated microspheres was in a direct relationship to the microsphere diameter. A first approach was based on coating the microspheres with poly(vinyl alcohol) followed by chemically crosslinking the coating layers that were in mutual contact. This method was disregarded because of the acute cytotoxicity of glutaraldehyde used as the crosslinking agent, the absence of macroporosity, and the complete lack of flexibility. A physical technique of aggregation was then tested, which relied on the plasticization of poly‐D,L‐lactide microspheres with triethylcitrate to the point where microspheres strongly adhered to each other when they were in contact. This method has proved to be straightforward and definitely superior to the chemical approach, particularly with respect to cytotoxicity, control of macroporosity, and flexibility. A polymer support was thus successfully produced which was biodegradable, macroporous (interconnected pores of 10–100 μm in diameter), and flexible. This potential medical device is presently being used for neuronal transplantation in the central nervous system. © 1995 John Wiley & Sons, Inc.
Development of fibroblast‐seeded ligament analogs for ACL reconstruction
Authors: Dunn Michael G. , Liesch Janice B. , Tiku Moti L. , Zawadsky Joseph P. 
Published: May 2005

AbstractWe fabricated “ligament analogs” in vitro, by seeding highstrength resorbable collagen fiber scaffolds with intraarticular (anterior cruciate ligament, ACL) or extraarticular (patellar tendon, PT) rabbit fibroblasts. Fibroblasts attached, proliferated, and secreted new collagen on the ligament analogs in vitro. Fibroblast function depended on the tissue culture substrate (ligament analog vs. tissue culture plate) and the origin of the fibroblasts (ACL vs. PT). PT fibroblasts proliferated more rapidly than ACL fibroblasts when cultured on ligament analogs. Collagen synthesis by ACL and PT fibroblasts was approximately tenfold greater on ligament analogs than on tissue culture plates. The composition, structure, and geometry of the collagen fiber scaffolds may promote collagen synthesis within ligament analogs in vitro., Ligament analogs roughly approximate the structure and strength of native ligament tissue. Ongoing in vivo studies suggest that autogenous fibroblast‐seeded ligament analogs remain viable after implantation into the knee joint. With further development, ligament analogs may be useful as implants for ACL reconstruction surgery. © 1995 John Wiley & Sons, Inc.
Physical crosslinking of collagen fibers: Comparison of ultraviolet irradiation and dehydrothermal treatment
Authors: Weadock Kevin S. , Miller Edward J. , Bellincampi Lisa D. , Zawadsky Joseph P. , Dunn Michael G. 
Published: May 2005

AbstractThe strength, resorption rate, and biocompatibility of collagenous biomaterials are profoundly influenced by the method and extent of crosslinking. We compared the effects of two physical crosslinking methods, ultraviolet irradiation (UV) (254 nm) and dehydrothermal (DHT) treatment, on the mechanical properties and molecular integrity of collagen fibers extruded from an acidic dispersion of type I bovine dermal collagen. Collagen fibers exposed to UV irradiation for 15 min had ultimate tensile strength (54 MPa) and modulus (184 MPa) values greater than or equivalent to values for fibers crosslinked with DHT treatment for 3 or 5 days. UV irradiation is a rapid and easily controlled means of increasing the mechanical strength of collagen fibers. Characterization of collagen extracted from the crosslinked samples by dilute acetic acid and limited pepsin digestion indicate that both UV and DHT treatments cause fragmentation of at least a portion of the collagen molecules. Partial loss of the native collagen structure may influence attachment, migration, and proliferation of cells on collagen fiberbased ligament analogs. These issues are currently being addressed in our laboratory. © 1995 John Wiley & Sons, Inc.
Delayed in vitro immune response to long‐term intraperitoneal polymer implant in mice
Authors: Maurin N. , Guernier C. , Daty N. 
Published: May 2005

AbstractThis paper presents an original experimental procedure designed to evaluate, by a two step in vivo/in vitro combination, the long‐term biocompatibility of synthetic materials developed for clinical applications. The efficacy of the test is illustrated by the experimental results obtained with various materials currently used in medicine (Dacron®, RCH®) and also with three recently synthesized compounds. In the first step of the procedure, the sample was grafted for at least 5 months in the peritoneal cavity of mice, allowing the possible development of delayed sensitization. In the second step, this sensitization was detected by an in vitro test, the Lymphoblastic Transformation Test (LTT), adapted for this new purpose. On the basis of this experiment, the 5 polymers tested were classified into 2 groups: one group did not significantly differ from the control, and the other had a significantly higher incidence of sensitization. As these results were in agreement with the known biocompatibility of these polymers, they demonstrate the validity of the test to classify new polymers. © 1995 John Wiley & Sons, Inc.