bluuebunny/crossref_metadata_2025 huggingface dataset:
Blood–biomaterial interactions in a flow system in the presence of bacteria: Effect of protein adsorption
Authors: Sapatnekar Suneeti , Kieswetter Kristine M. , Merritt Katharine , Anderson James M. , Cahalan Linda , Verhoeven Michel , Hendriks Marc , Fouache Benedicte , Cahalan Patrick
Published: December 2004

An in vitro continuous flow system with whole human blood was used to study blood–biomaterial interactions on a base polyurethane and three modified surfaces in the presence and absence of circulating Staphyloccus epidermidis. We hypothesized that the composition of the protein layer adsorbed on the surface of the biomaterial would influence the response of blood components and bacteria. We examined the test surfaces for adsorption of nine plasma proteins and adsorption profiles differed on the four surfaces. The positively charged surface, UC, adsorbed significantly higher amounts of fibronectin (P < .01), von Willbrand factor (P < .01), and fibrinogen (P < .05) than the other materials. As a consequence of increased adsorption of these adhesive proteins, the adhesion of platelets and bacteria was greater on UC than on any other surface. On the base polyurethane, BC, and the negatively charged surface, UA, protein adsorption was low, and these materials were largely free of adherent blood cells and bacteria. The heparinized surface, UH, adsorbed higher quantities (P < .01) of Hageman factor and high molecular weight kininogen relative to the other surfaces. Platelet adhesion, and surface coagulation were prominent on UC, and may have contributed to increased bacterial adhesion on this surface. In the presence of circulating bacteria, adsorption was generally lower than in the absence of bacteria. The pattern of protein adsorption was largely unaffected by the strain of circulating bacteria, but platelet responses (adhesion and activation) were greater in the presence of slime‐producing S. epidermidis as compared to the non‐slime‐producing strain, suggesting that slime may have a direct activating effect on platelets. © 1995 John Wiley & Sons, Inc.
Influence of discharge power level on the properties of hydroxyapatite films deposited on Ti6A14V with RF magnetron sputtering
Authors: van Dijk K. , Schaeken H. G. , Wolke J. C. G. , Marée C. H. M. , Habraken F. H. P. M. , Verhoeven J. , Jansen J. A.
Published: December 2004

The effects of discharge radiofrequency (RF) power and film thickness were studied on the characteristics of Ca5(PO4)3OH (hydroxyapatite) thin films fabricated by RF magnetron sputtering. The structure and chemical composition were investigated with α‐step (thickness), scanning electron microscopy (SEM), X‐ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), and infrared absorption spectrometry (FTIR). The films were analyzed assputtered and after annealing at 550°C under argon flow. SEM showed that the film surfaces had no cracks or other defects. X‐ray diffraction showed that the deposited films were amorphous with low‐discharge RF power, and crystalline with high‐discharge RF power. After annealing, all the films had the same crystalline structure as apatite. However, the RBS measurements revealed that all films had a higher calcium–phosphate ratio than standard synthetic hydroxyapatite. Furthermore, statistical testing of the RBS data revealed the existence of only a weak correlation between the Ca/P ratio and the discharge power level. Although all sputtered films showed phosphate bonds in the infrared spectrum, only after annealing did the OH bonds of hydroxyapatite become visible. © 1995 John Wiley & Sons, Inc.
The incorporation and sustained release of bioactive insulin from a bead‐formed macroporous hydrogel matrix
Authors: Atkins Terence W. , McCallion Roisin L. , Tighe Brian J.
Published: December 2004

Freeze‐thaw photopolymerization of a mixed solution of monomers and bovine insulin around frozen ice crystals has been used to generate a bead‐formed macroporous hydrophilic matrix of p‐HEMA. The largest proportion of beads was 500–1000 μm in size (distribution <106–1700 μm) with a mean EBC of 71.7 ± 0.92%. Insulin release was monitored using RIA and insulin bioactivity determined using the rate of insulin stimulated D‐[U14C] glucose oxidation to 14CO2. The cumulative insulin release profile was characterized by an initial lag phase followed by an almost linear increase in insulin release for up to 30 days. Insulin release at 4°C was significantly greater than release at 37°C both in the presence and absence of 2.5% thiomersalate as preservative. The latter served to extend the time period over which significant insulin release could be detected. Increasing the monomer concentration decreased the mean equilibrium buffer content (EBC), the total mean cumulative release of insulin, and the proportion of the incorporated insulin load subsequently released at both 4°C and 37°C in the presence of preservative. Insulin determination using RIA and bioassay confirmed that insulin released from beads was bioactive and that immunoreactivity was a reasonably reliable indicator of bioactivity. © 1995 John Wiley & Sons, Inc.
The effects of centrifugation and titanium fiber reinforcement on fatigue failure mechanisms in poly(methyl methacrylate) bone cement
Authors: Topoleski L. D. Timmie , Ducheyne Paul , Cuckler John M.
Published: December 2004

The contributions to fatigue resistance in poly(methyl methacrylate) bone cement (PMMA) by centrifugation and titanium fiber addition were studied. Three modified bone cements were tested: porosity reduced cement (C‐PMMA); titanium (Ti) fiber‐reinforced cement (R‐PMMA), using a novel method to incorporate fibers; and porosity reduced and Ti fiber‐reinforced cement (C‐R‐PMMA). Specimens of untreated bone cement (PMMA) were included as controls. Non‐notched and notched specimens were cyclically loaded in fully reversed bending. For the non‐notched specimens, at all stress levels, C‐R‐PMMA had significantly greater fatigue life than either C‐PMMA or R‐PMMA (except C‐PMMA at 30 MPa). R‐PMMA had lower fatigue life than the control at 30 MPa (nominal maximum stress), but higher fatigue life at 20 and 15 MPa. At both 20 and 15 MPa, there was no statistical difference between the fatigue lives of C‐PMMA and R‐PMMA. Fractography revealed that, at 30 MPa, characteristics of rapid fracture predominated. At 20 and 15 MPa, in contrast, almost the entire fracture surface showed the characteristic fatigue morphology, indicating that subcritical crack growth was predominant. For the notched specimens, C‐PMMA showed greater life than PMMA at the highest stress intensity, but the lifetimes converged with decreasing stress intensity. In contrast, the lifetimes for PMMA and R‐PMMA diverged with decreasing stress intensity. The effect of centrifugation appeared to be strongest at higher stress intensities, and diminished with decreasing stress intensity. The reinforcing effect of Ti fiber addition increased the notched fatigue life at high initial stress intensities, and the reinforcing effect increased with decreased stress intensity. In both the non‐notched and notched fatigue experiments, the combination of porosity reduction and Ti fiber reinforcement (C‐R‐PMMA) led to substantial improvements in fatigue life at each stress and stress intensity level, suggesting that Ti fiber reinforcement and porosity reduction effects are additive. Fiber reinforcement affects the fatigue crack propagation phase of failure in bone cement, enhancing the fatigue crack propagation resistance. Pore reduction may affect fatigue crack initiation as well as fatigue crack propagation resistance. © 1995 John Wiley & Sons, Inc.
In vivo calcium phosphate formation induced by sol—gel‐prepared silica
Authors: Li Panjian , Ye X. , Kangasniemi I. , de Blieck‐Hogervorst J. M. A. , Klein C. P. A. T. , de Groot K.
Published: December 2004

Implantation with plugs made of a porous sol‐gel‐prepared silica into the femurs of goats demonstrated that a calcium phosphate was formed both on the silica plugs and within the pores inside the silica plugs 12 weeks postoperatively. This observation indicates that a highly hydrated silica surface is effectively catalytic for calcium phosphate nucleation. Calcification can be triggered in physiologic solution under stimulation of the silica gel. A high level of silicon in the uncalcified osteoid region of young bone is thus thought to provide a number of SiOH groups for initiating calcium phosphate formation. Our results provide some information about the mechanism of calcium phosphate mineralization in higher animals. We believe that heterogeneous nucleation of apatite can be induced from metastable calcium phosphate solutions including physiologic fluids on those specific surfaces of materials, where there are abundant acidic OH groups. © 1995 John Wiley & Sons, Inc.
Apatite coated on organic polymers by biomimetic process: Improvement in its adhesion to substrate by glow‐discharge treatment
Authors: Tanahashi M. , Yao T. , Kokubo T. , Minoda M. , Miyamoto T. , Nakamura T. , Yamamura T.
Published: December 2004

A dense, uniform, and highly biologically active bone‐like apatite layer can be formed in arbitrary thickness on any kind and shape of solid substrate surface by the following biomimetic method at ordinary temperature and pressure: First, a substrate is set in contact with particles of bioactive CaOSiO2‐based glass soaked in a simulated body fluid (SBF) with inorganic ion concentrations nearly equal to those of human blood plasma so that a number of apatite nuclei are formed on the substrate. Second, the substrate is soaked in another solution with ion concentrations 1.5 times those of SBF (1.5SBF) so that the apatite nuclei grow in situ. In the present study, organic polymer substrates were treated with glow‐discharge in O2 gas atmosphere, then subjected to the above‐mentioned biomimetic process. The induction periods for the apatite nucleation on all the examined organic polymers were reduced from 24 to 6 h, with glow‐discharge treatment. The adhesive strengths of the formed apatite layer to the substrates increased from about 4 to 10 MPa for poly(ethylene terephthalate) and poly‐ether sulfone, and from 1 ∼ 2 to 6 ∼ 7 MPa even for poly(methyl methacrylate), polyamide 6 and polyethylene. It is supposed that highly polar groups such as carbonyl, ester, hydroxyl, and carboxyl ones formed by glow‐discharge treatment increased the affinity of a silicate ion with the substrates to decrease the induction period, and also increased the affinity of the apatite with the substrate to increase the adhesive strength. The apatite‐organic polymer composites thus obtained are expected to be useful as bone‐repairing materials as well as soft tissue‐repairing materials. © 1995 John Wiley & Sons, Inc.
Adsorption–Desorption of proteins on phospholipid polymer surfaces evaluated by dynamic contact angle measurement
Authors: Ueda Tomoko , Ishihara Kazuhiko , Nakabayashi Nobuo
Published: December 2004

Adsorption‐desorption of plasma protein on various polymer membranes was evaluated by a dynamic contact angle (DCA) measurement using the Wilhelmy plate method. Poly(ethylene terephthalate) (PET) was used as a substrate membrane; we examined this membrane coated with hydrophilic polymers such as poly[2‐methacryloyloxyethyl phosphorylcholine (MPC)‐co‐n‐butyl methacrylate (BMA)] or poly[2‐hydroxyethyl methacrylate (HEMA)]. Although the λ‐potential of the PET membrane was negative, the coating with poly(MPC‐co‐BMA) induced increase of value to nearly zero. The DCA loops observed on the polymer membranes after protein adsorption were unity and hysteresis of the loop was reduced. In the cases of protein adsorbed on both the PET and the poly(HEMA) membranes, the shape and hysteresis of the loops were almost same during the rinsing process with a phosphate‐buffered solution (PBS). However, the hysteresis of the DCA loops that appeared on the protein‐adsorbed poly(MPC‐co‐BMA) membrane became large during the rinsing process with the PBS, and the shape of the DCA loop returned to its non‐protein‐adsorbed state. Therefore, proteins adsorbed on poly(MPC‐co‐BMA) could desorb more readily than those on PET and poly(HEMA) because of the weak interaction between poly(MPC‐co‐BMA) and the proteins. © 1995 John Wiley & Sons, Inc.
Effect of titanium surface roughness on proliferation, differentiation, and protein synthesis of human osteoblast‐like cells (MG63)
Authors: Martin J. Y. , Schwartz Z. , Hummert T. W. , Schraub D. M. , Simpson J. , Lankford J. , Dean D. D. , Cochran D. L. , Boyan B. D.
Published: December 2004

The effect of surface roughness on osteoblast proliferation, differentiation, and protein synthesis was examined. Human osteoblast‐like cells (MG63) were cultured on titanium (Ti) disks that had been prepared by one of five different treatment regimens. All disks were pretreated with hydrofluoric acid‐nitric acid and washed (PT). PT disks were also: washed, and then electropolished (EP); fine sandblasted, etched with HCl and H2SO4, and washed (FA); coarse sandblasted, etched with HCl and H2SO4, and washed (CA); or Ti plasma‐sprayed (TPS). Standard tissue culture plastic was used as a control. Surface topography and profile were evaluated by brightfield and darkfield microscopy, cold field emission scanning electron microscopy, and laser confocal microscopy, while chemical composition was mapped using energy dispersion X‐ray analysis and elemental distribution determined using Auger electron spectroscopy. The effect of surface roughness on the cells was evaluated by measuring cell number, [3H]thymidine incorporation into DNA, alkaline phosphatase specific activity, [3H]uridine incorporation into RNA, [3H]proline incorporation into collagenase digestible protein (CDP) and noncollagenase‐digestible protein (NCP), and [35S]sulfate incorporation into proteoglycan.

Based on surface analysis, the five different Ti surfaces were ranked in order of smoothest to roughest: EP, PT, FA, CA, and TPS. A TiO2layer was found on all surfaces that ranged in thickness from 100 Å in the smoothest group to 300 Å in the roughest. When compared to confluent cultures of cells on plastic, the number of cells was reduced on the TPS surfaces and increased on the EP surfaces, while the number of cells on the other surfaces was equivalent to plastic. [3H]Thymidine incorporation was inversely related to surface roughness. Alkaline phosphatase specific activity in isolated cells was found to decrease with increasing surface roughness, except for those cells cultured on CA. In contrast, enzyme activity in the cell layer was only decreased in cultures grown on FA‐ and TPS‐treated surfaces. A direct correlation between surface roughness and RNA and CDP production was found. Surface roughness had no apparent effect on NCP production. Proteoglycan synthesis by the cells was inhibited on all the surfaces studied, with the largest inhibition observed in the CA and EP groups. These results demonstrate that surface roughness alters osteoblast proliferation, differentiation, and matrix productionin vitro. The results also suggest that implant surface roughness may play a role in determining phenotypic expression of cellsin vivo.
Surface characteristics and properties of lumbrokinase‐immobilized polyurethane
Authors: Ryu Gyu Ha , Han Dong Keun , Park Seonyang , Kim Miran , Kim Young Ha , Min Byounggoo
Published: December 2004

Potent and novel fibrinolytic enzymes (lumbrokinase [LK]) were extracted from the earthworm, Lumbricus rubellus. These enzymes were very stable and showed greater antithrombotic activity than other currently used fibrinolytic proteins. An LK fraction showing the most potent fibrinolytic activity was immobilized onto a polyurethane (PU) surface to investigate its enzymatic activity and antithrombotic activity. A methanol‐extracted PU surface was coated with 3% (wt/vol) maleic anhydride methylvinyl ether copolymer (MAMEC)/tetrahydrofuran (THF) solution, and the surface was incubated in an LK solution/phosphate‐buffered saline (PBS, pH 7.4). The surface properties were characterized by attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR), electron spectroscopy for chemical analysis (ESCA), and dynamic contact angle. The stability of immobilized LK was determined by caseinolytic activity assay and the specificity of immobilized LK on fibrinogen/fibrin was observed by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis (SDS‐PAGE). The antithrombotic activity of immobilized LK was evaluated using an ex vivo rabbit A‐A shunt experiment. LK immobilization was confirmed by ATR‐FTIR and ESCA. Immobilized LK demonstrated stable proteolytic activity during various incubation periods. Immobilized LK proteolyzed fibrinogen and fibrin almost specifically, while it hardly hydrolyzed other plasma proteins including plasminogen and albumin. In the ex vivo A‐A shunt experiment, the LK‐immobilized surface significantly prolonged occlusion time over control surfaces. This is primarily due to the high thrombolytic activity of immobilized LK. In this work, a highly efficient surface modification method on the PU surface was developed, and this LK immobilization technique will be very useful in improving the blood compatibility of blood‐contacting devices. © 1995 John Wiley & Sons, Inc.
In vitro fatigue testing of a dental bonding system on enamel
Authors: Ruse N. D. , Shew R. , Feduik D.
Published: December 2004

The aim of this study was to investigate the in vitro fatigue behavior of a dental bonding system [ScotchBond Multi Purpose (SBMP)] by using a cyclic shear loading test. Cylinders of a light‐cured hybrid composite resin (Z100) were formed on, and bonded with SBMP to, the flattened, acid‐etched enamel surface of human teeth. Thirty‐two samples (eight per group) were used to determine the 1‐h, 1‐day, 7‐day, and 30‐day shear bond strengths. For the shear fatigue test, the stress was cycled, at a rate of 1Hz, between 0 and a preset value in the 12–28 MPa range (from ‐3 SD to + 1 SD around the 24‐MPa mean bond strength of the 1‐h specimens). The applied stress and the number of cycles to failure were recorded for each of the 75 samples tested (15 samples per set‐stress). Three stress versus number of cycles curves (low, median, and high S‐N curves) were obtained and an approximate endurance limit of 10 MPa was identified for the SBMP bonding system. The data obtained explain, in part, the discrepancy between in vitro and in vivo results and underline the difficulty of predicting the in vivo behavior based on results of in vitro bond strength tests alone. Shear fatigue test data, however, could provide a better insight into the long‐term in vivo behavior of a dental bonding system. © 1995 John Wiley & Sons, Inc.
Wettability and interfacial interactions in bioceramic‐body‐liquid systems
Authors: Agathopoulos S. , Nikolopoulos P.
Published: December 2004

Wetting experiments, by the sessile drop technique, were carried out at 37°C in air to determine the surface and interfacial interactions that take place in various solid bioceramics based on Al2O3, ZrO2(YPZ), SiO2, and TiO2 in contact with water, Ringer solution, artificial synovial fluid, calf serum, human plasma, and whole blood (+ EDTA). The surface energy of the liquids was measured by the ring method. The calculated values of the energy of interaction (work of adhesion) reveal that intermolecular forces act across the solid‐liquid interfaces. The contribution of the dispersion and polar interactions to the surface energy of the polar liquids and the pure or mixed oxides was determined assuming that in the system of Mn‐steel‐liquids only dispersion forces act at the interface. It was found that the contribution of the polar interactions to the energy of interaction at the solid‐liquid interface increases with the glassy phase content of the oxide that causes reduction of the measured contact angle. © 1995 John Wiley & Sons, Inc.
Effect of parallel surface microgrooves and surface energy on cell growth
Authors: Den Braber E. T. , de Ruijter J. E. , Smits H. T. J. , Ginsel L. A. , von Recum A. F. , Jansen J. A.
Published: December 2004

To evaluate the effect of surface treatment and surface microtexture on cellular behavior, smooth and microtextured silicone substrata were produced. The microtextured substrata possessed parallel surface grooves with a width and spacing of 2.0 (SilD02), 5.0 (SilD05), and 10 μm (SilD10). The groove depth was approximately 0.5 μm. Subsequently, these substrata were either left untreated (NT) or treated by ultraviolet irradiation (UV), radiofrequency glow discharge treatment (RFGD), or both (UVRFGD). After characterization of the substrata, rat dermal fibroblasts (RDF) were cultured on the UV, RFGD, and UVRFGD treated surfaces for 1, 3, 5, and 7 days. Comparison between the NT and UV substrata revealed that UV treatment did not influence the contact angles and surface energies of surfaces with a similar surface topography. However, the contact angles of the RFGD and UVRFGD substrata were significantly smaller than those of the UV and NT substrata. The dimension of the surface microevents did not influence the wettability characteristics. Cell culture experiments revealed that RDF cell growth on UV‐treated surfaces was lower than on the RFGD and UVRFGD substrata. SEM examination demonstrated that the parallel surface grooves on the SilD02 and SilD05 substrata were able to induce stronger cell orientation and alignment than the events on SilD10 surfaces. By combining all of our findings, the most important conclusion was that physicochemical parameters such as wettability and surface free energy influence cell growth but play no measurable role in the shape and orientation of cells on microtextured surfaces. © 1995 John Wiley & Sons, Inc.
Metabolic response of granulocytes and platelets to synthetic vascular grafts: Preliminary results with an in vitro technique
Authors: Pärsson Håkan , Nässberger Lennart , Thörne Johan , Norgren Lars
Published: December 2004

The metabolism of granulocytes as well as platelets evoked by incubation with different synthetic vascular grafts was monitored during 6‐h batch experiments using microcalorimetry. Standard knitted Dacron grafts, ePTFE‐grafts, knitted Dacron grafts with collagen impregnation, and knitted Dacron grafts with external collagen‐coating were used. The heat production per cell was calculated. A rapid increase of metabolic activity followed by a gradual decrease was demonstrated with both granulocyte suspension and platelet concentrate. Significant differences were obtained between the materials with a maximum response of Dacron grafts with collagen impregnation for both granulocyte and platelet response. The materials had different surface morphologies regarding cell adhesion after incubation as demonstrated with scanning electron microscopy with more pronounced adhesion on the collagen‐impregnated grafts. The results suggest that macrocalorimetry may be useful for the evaluation of cellular reactions on different biomaterials. However, further studies have to reveal the specificity of the reactions. © 1995 John Wiley & Sons, Inc.
Surface and blood‐contacting properties of alkylsiloxane monolayers supported on silicone rubber
Authors: Silver James H. , Hergenrother Robert W. , Lin Jui‐Che , Lim Florencia , Lin Horng‐Ban , Okada Toshiyuki , Chaudhury Manoj K. , Cooper Stuart L.
Published: December 2004

Self‐assembled monolayers of alkylsiloxanes supported on polydimethyl siloxane (PDMS) rubber were used as model systems to study the relation between blood compatibility and surface chemistry. The inner lumen of PDMS tubes was first treated with an oxygen plasma. The resultant oxidized surfaces were postderivatized by reacting them with alkyltrichlorosilanes to form the monolayer films. The chemical properties of the monolayers were controlled by varying the head‐group chemical compositions. Surface derivatization was verified using variable‐angle X‐ray photoelectron spectroscopy (XPS or ESCA). Blood compatibility was evaluated using a canine ex vivo arteriovenous series shunt model. Surfaces grafted with hydrophobic head‐groups as ‐CH3 and ‐CF3 had significantly lower platelet and fibrinogen deposition than the surfaces composed of hydrophilic groups such as ‐CO2CH3, ‐(CH2CH2O)3COCH3, and ‐(OCH2CH2)3OH. © 1995 John Wiley & Sons, Inc.
Bioactive bone cement: The effect of amounts of glass powder and histologic changes with time
Authors: Tamura Jiro , Kawanabe Keiichi , Yamamuro Takao , Nakamura Takashi , Kokubo Tadashi , Yoshihara Satoru , Shibuya Takehiro
Published: December 2004

A study was conducted to examine the influence of the amount of glass powder added to a bioactive bone cement of our formula on its mechanical and biologic properties. Serial changes in the cement with time were also examined. The bioactive bone cement consisted of CaO‐SiO2P2O5CaF2 glass powder and bisphenol‐a‐glycidyl methacrylate resin. Glass powder was added to the cement in 30, 50, 70, and 80% weight ratios. The compressive strengths of the resulting cements (171–239 MPa) were more than double that of polymethylmethacrylate cement (68 MPa). Histologic examination of rat tibiae bearing artificial defects packed with each bioactive cement showed direct bone contact 4 weeks after surgery. The cement with a higher percentage of glass powder showed better direct formation of bone around its periphery with a thicker reactive layer. Under scanning electron microscopic observation, the reactive layer showed increased levels of calcium and phosphorus. Examination of histologic changes up to 26 weeks showed progressive bone formation around the cement and no sign of biodegradation. © 1995 John Wiley & Sons, Inc.
Dynamic creep behavior of acrylic bone cement
Authors: Verdonschot Nico , Huiskes Rik
Published: December 2004

Recent studies concerning the fixation of cemented total hip arthroplasty (THA) have led to new hypotheses about the dynamic, long‐term failure mechanisms leading to prosthetic loosening. As a result, the long‐term mechanical behavior of acrylic bone cement has gained more interest since little is known about these properties. In this study, the dynamic, compressive creep deformation of acrylic bone cement was examined. An amount of creep was found, with creep strains exceeding the elastic strain during 14 × 106 loading cycles. There was a linear relationship between the logarithmic values of the number of loading cycles and the creep strain. The effect of stress level on the amount of creep was different from that in results of static experiments reported in the literature. Comparing the results with tensile creep experiments revealed that bone cement under a tensile load creeps much quicker than under a compressive one. Young's modulus was significantly higher when the material was loaded at higher strain rates. The bone cement became stiffer with an increasing number of loading cycles. The creep behavior of bone cement is important for the long‐term behavior of cemented THA. It enables subsidence of the stem and attenuation of stress peaks in the cement mantle. © 1995 John Wiley & Sons, Inc.
Determination of the mineral phases and structure of the bone‐implant interface using raman spectroscopy
Authors: Leung Yiuchong , Anton Walters M. , Blumenthal Norman C. , Ricci John L. , Spivak Jeff M.
Published: December 2004

The bone‐implant interface formed in a canine distal femur was examined by means of a Raman microprobe using an implant model designed to test calcium phosphate surface coatings. By using the 960 cm−1 band of calcium phosphate to characterize the interface and adjacent mineral, we obtained spatial and compositional information about the attachment of bone to the synthetic calcium phosphate coating on a titanium support. The interface between bone and the synthetic calcium phosphate is approximately 30–40 μm in width. © 1995 John Wiley & Sons, Inc.
Evaluating the dialine® vascular prosthesis knitted from an alternative source of polyester yarns
Authors: King Martin W. , Marois Yves , Guidoin Robert , Ukpabi Pauline , Deng Xiaoyan , Martin Louisette , Pǎris Edouard , Douville Yvan
Published: December 2004

The sudden and unilateral decision by E. I. DuPont de Nemours & Co., Inc., to withdraw its polymers for use in implantable devices has presented the medical device industry with an immediate and serious challenge to find alternative sources of biomaterials. In France, the company Cardial S. A. has already taken steps to find an alternative polyester yarn to replace Dacron® by developing a new arterial prosthesis knitted from polyester yarns supplied by Rhǒne‐Poulene Fibres. This article describes an in vitro and in vivo study of this French device, called the Dialine® prosthesis, with a view to determining its relative performance compared to current American and British prostheses, which rely on DuPont's Dacron® yarn. In addition to analyses of the morphology and textile structure, and measurements of its physical and chemical properties, the Dialine® graft was implanted as a thoracoabdominal bypass in dogs for periods ranging from 4 h to 6 months. In addition to our pathologic and histologic observations, we cleaned and evaluated the explanted prostheses for in vivo changes in dimensions, strength, and crystalline microstructure. The Dialine® graft was found to differ structurally from other polyester prostheses because it is warp‐knitted from a mixture of flat and texturized yarns with finer filaments. Its denser structure has a lower water permeability, greater flexibility and ease of handling, satisfactory strength, and dimensional stability, and it presents different textures on its luminal and external surfaces. The in vivo trial demonstrated that it has excellent biocompatibility and biostability over 6 months. With no thrombi observed on the luminal surface after 3 months, it has a faster rate of healing, generates compact external and internal capsules with a thinner neointima, and has an overall milder inflammatory response than is normally observed with Dacron®‐based prostheses. © 1995 John Wiley & Sons, Inc.
Effect of nickel‐based dental casting alloys on fibroblast metabolism and ultrastructural organization
Authors: Bumgardner J. D. , Doeller J. , Lucas L. C.
Published: December 2004

Previous cell culture evaluations have shown that nickel–chromium dental alloys did not affect cellular viability or morphology. However, nickel‐based alloys released corrosion products which decreased cellular proliferation. It was hypothesized that this decrease was due to an interference of cellular energy metabolism by released metal ions. To test this hypothesis, we evaluated the effects on cellular energy metabolism, adenosine triphosphate (ATP) levels, and cellular ultrastructure by four nickel‐based alloys, including high and low chromium alloys with and without beryllium additions, in human gingival fibroblast cell culture. Energy metabolism was evaluated by measuring glucose‐6‐phosphate dehydrogenase (G‐6‐PDH) activity. ATP levels were measured with the luciferin–luciferase method. Cellular membranes and ultrastructural organization were evaluated by scanning and transmission electron microscopy. The results of this study showed that metal ions released from all alloys completely inhibited G‐6‐PDH activity and reduced cellular ATP levels as compared to controls. The reduction in intracellular ATP was greater for the beryllium containing alloys than the non‐beryllium‐containing alloys. However, no morphologic changes in cellular membranes or organelles were observed. These results support the hypothesis that metal ions released from nickel‐based dental casting alloys interfere with cellular energy metabolism. © 1995 John Wiley & Sons, Inc.
Contribution of vascular catheter material to the pathogenesis of infection: The enhanced risk of silicone in vivo
Authors: Sherertz Robert J. , Carruth William A. , Marosok Randy D. , Espeland Mark A. , Johnson Russ A. , Solomon Donald D.
Published: December 2004

There is currently very little information to suggest that polymer materials used to make vascular catheters differ in their risk of infection. A rabbit model of subcutaneous Staphylococcus aureus infection was used to determine the relative risk of infection associated with silicone, polyurethane, polyvinylchloride, and Teflon® catheters. Seven days after catheter implantation and inoculation with S. aureus, catheters were observed for gross purulence and quantitatively cultured. Silicone catheters were found to have a greater risk of grossly apparent infection (purulence) and a greater number of organisms removed from catheters by quantitative culture than the other three catheter materials (P < .01). The risk of infection associated with silicone catheters decreased (P < .05) if the S. aureus inoculation was delayed for 2 days or if the histology of the inflammatory response around the four catheter materials was evaluated at either 2 or 7 days after catheter insertion with or without S. aureus inoculation. Silicone catheters had greater associated inflammation (P < .05) with or without S. aureus inoculation. These results suggest that silicone catheter materials may have unique properties that increase the risk of infection after implantation. Further studies should be done to understand the mechanism(s) of these observations. © 1995 John Wiley & Sons, Inc.
Platelet activation by healing EPTFE grafts
Authors: Keith Ozaki C. , Contreras Mauricio , Phaneuf Matthew , Sheppeck Richard A. , Rutter Carolyn M. , Quist William C. , Logerfo Frank W.
Published: December 2004

The purpose of this study was to examine the effect of the in vivo maturing ePTFE graft surface on platelet activation. Ten canines were randomized to receive either a carotid to infrarenal aorta ePTFE graft or sham operation. Animals were sampled at specific time points up to 3 months post‐operatively. Whole blood platelet aggregometry (arachidonic acid, ADP, and collagen agonists) and ATP secretion (in response to arachidonic acid, ADP, collagen, and thrombin) were measured. Additionally, complete hematologic analysis and histology were performed. With time, graft animals showed significantly more decrease in platelet aggregation in response to ADP compared to sham animals (P = .023). The total amount of ATP per platelet was not different, as demonstrated by equivalent ATP release per platelet in response to thrombin. Over the first week, grafted dogs developed a decrease in systemic platelet count of 50% (P < .001) that persisted over the 3‐month follow‐up period. With time, overall regression model slopes of graft and sham platelet count data were not statistically different (P = .29). Histologically, the grafts demonstrated limited cellular ingrowth at both anstomoses, with fibrin matrix along the remainder of the blood‐biomaterial interface. These data suggest that, similar to Dacron, exposure to an ePTFE surface results in significant changes in platelet biology, and these platelet–ePTFE interactions persist even after the graft has formed a mature pseudointima. The pseudointima appears to be the primary determinant of the blood–biomaterial interaction. © 1995 John Wiley & Sons, Inc.
Control of contact activation on end‐point immobilized heparin: The role of antithrombin and the specific antithrombin‐binding sequence
Authors: Sanchez J. , Elgue G. , Riesenfeld J. , Olsson P.
Published: December 2004

The uptake and activation of FXII from blood plasma was studied in small‐diameter polyethylene tubing, surface‐modified by end‐point immobilization of heparin. Two preparations of heparin were used to modify the contact‐activating properties of the plastic tubing: unfractionated, functionally active heparin and low‐affinity heparin, lacking the specific antithrombin‐binding sequence and virtually devoid of anticoagulant activity. The uptakes of FXII on the two heparin surfaces were similar. No activated FXII could be demonstrated on the unfractionated heparin surface, whereas on the low‐affinity heparin surface nearly all FXII underwent spontaneous activation. The suppression of FXII activation on the unfractionated heparin surface was investigated by using plasma depleted of antithrombin, complement C1 esterase inhibitor, or both. The removal of antithrombin resulted in extensive activation of FXII, whereas the depletion of C1 esterase inhibitor had only a minor effect. Experiments with recalcified plasma showed rapid clot formation during exposure to the low‐affinity heparin surface. After depletion of antithrombin, but not complement C1 esterase inhibitor, the recalcified plasma clotted in contact with the unfractionated heparin surface as well. We conclude that antithrombin and the antithrombin‐binding sequence in the surface‐immobilized heparin are essential for the prevention of surface activation of FXII and triggering of the intrinsic coagulation system. © 1995 John Wiley & Sons, Inc.
Effect of self‐reinforced polyglycolide membranes on cortical bone: An experimental study on rats
Authors: Ashammakhi N. , Mäkelä E. A. , Vihtonen K. , Rokkanen P. , Törmälä P.
Published: December 2004

A self‐reinforced polyglycolide (SR‐PGA) membrane has been developed recently by our research group and testing of it begun. To study the behavior of this membrane and its effect on cortical bone, 93 Wistar rats were operated on. SR‐PGA membrane was applied around the rats' femoral diaphyses, either over the periosteum or directly over the bone, after periosteal stripping. In a control group no membrane was applied, but the femoral periosteum was stripped away. The rats were sacrificed 1, 3, 6, 12, 24, and 30 weeks postoperatively. Radiology, histology, oxytetracycline fluorescence labeling, microradiography, and planimetry were used to determine the outcome. A fibrous tissue capsule had formed around and replaced the membrane. SR‐PGA membrane had a positive effect on new bone formation. Callus was frequently seen proximally and distally to the implant. Periosteal thickening occurred whether or not SR‐PGA membrane was used. PGA fibers decreased in number and diameter continuously until they vanished by 30 weeks. No infections or adverse reactions were encountered. Accordingly, SR‐PGA membrane is considered to be biocompatible and applicable in the treatment of cortical bone lesions such as comminuted fractures and defects. © 1995 John Wiley & Sons, Inc.
Augmentation of meniscal repairs with cyanoacrylate glue
Authors: Koukoubis Theodosios D. , Glisson Richard R. , Feagin John A. , Seaber Anthony V. , Vail Thomas Parker
Published: December 2004

Cyanoacrylate glues are biodegradable, bacteriostatic, hemostatic adhesives which have been used experimentally in surgical procedures on many tissues. This study evaluates the efficacy of cyanoacrylate glues used for in vitro bovine meniscus repair. Our hypothesis was that a local adhesive might improve fixation of meniscus tears reapproximated with suture, or obviate the need for suture. Three highviscosity flexible cyanoacrylate glues were tested and their tensile strengths compared to those of suture alone and suture augmented with glue. The flexible formulation enables the glue to deform with the meniscus during movement of the knee joint. Bovine meniscus tissue was used as the model to compare the tensile strength at the meniscus repair site using the 300 cps glue in combination with 3‐0 prolene suture, 300 cps cyanoacrylate glue alone, and suture alone. Twenty specimens were included in each repair group, and the peak load to failure was normalized for surface area and subjected to analysis of variance. Results of the analysis showed that the peak load to failure of the combination of cyanoacrylate glue plus suture was significantly higher than that of glue alone (P < .0001), but not significantly higher than that of suture alone (P = .18). However, in tissues repaired with suture, tissue separation at the tear site was noted almost immediately after distraction started, as a result of the elasticity of the suture. The combination of cyanoacrylate glue plus suture provided the maximum tensile strength before tissue separation. Because tissue separation may interfere with the meniscal healing process, glue used in combination with suture appears to offer some advantage mechanically. The cyanoacrylate formulations studied did not seem suitable for use without suture in meniscus repair. © 1995 John Wiley & Sons, Inc.
Development of surface photochemical modification method for micropatterning of cultured cells
Authors: Matsuda Takehisa , Sugawara Takashi
Published: December 2004

This article reports the development of micropatterning technology fo cultured cells by precise surface regional modification via photochemical fixation of phenyl azidoderivatized polymers on polymer surfaces. Photoreactive polymers prepared in this study included poly(N,N, ‐dimethylacrylamide‐co‐3‐azidostyrene), bis‐4‐azidobenzamide‐polyethylene glycol, and poly(styre‐co‐3‐azido‐styrene). The photochemical fixation of these photoreactive polymers consisted of three steps: (1) coating of a photoreactive polymer on a material surface, (2) ultraviolet irradiation through a photomask, and (3) removal of nonreacted polymer by a solvent. Electron spectroscopy for chemical analysis and water contact angle measurement were employed for surface characterization. Two different types of regionally modified surfaces were prepared; one was a hydrophilic polymer regionally fixed on a tissue culture dish and the other was a hydrophobic polymer regionally fixed on poly(vinyl alcohol) (PVA). Photochemical surface microfabrication permits μ‐order dimensional precision, which was verified by the micropatterned tissue formation of bovine aorta endothelial cells (ECs) when ECs were seeded on these surfaces. ECs adhered, spread, and confluently proliferated only on uncoated tissue culture dish surfaces or hydrophobic regions on PVA. Thus, the regionally differentiated cell adhesional regions were created by photo chemically driven surface microprocessing. © 1995 John Wiley & Sons, Inc.
Mechanical properties of the binary titanium‐zirconium alloys and their potential for biomedical materials
Authors: Kobayashi Equo , Matsumoto Shigeru , Doi Hisashi , Yoneyama Takayuki , Hamanaka Hitoshi
Published: December 2004

Mechanical properties of titanium‐zirconium binary alloys were investigated in order to reveal their possible use for new biomedical materials and to collect useful data for alloy design through a hardness test, a tensile test, and optical microscopy. The hardness of the alloy containing 50% zirconium was approximately 2.5 times as large as the hardness of pure titanium and pure zirconium. Tensile tests showed a similar tendency. No changes between hardness of as cast specimens and as homogenized specimens were observed, nor were changes in microstructures noted. Comparisons between the Ti‐6Al‐4V alloy and the Ti‐Zr‐6Al‐4V alloy indicated that a titanium‐zirconium alloy could provide a base material for a new biomedical alloy. From these results, it was concluded that new alloys for biomedical materials should be designed as titanium‐zirconium base alloys. © 1995 John Wiley & Sons, Inc.
Biodegradable sponges for hepatocyte transplantation
Authors: Mooney D. J. , Park S. , Kaufmann P. M. , Sano K. , McNamara K. , Vacanti J. P. , Langer R.
Published: December 2004

Liver cell transplantation may provide a means to replace lost or deficient liver tissue, but devices capable of delivering hepatocytes to a desirable anatomic location and guiding the development of a new tissue from these cells and the host tissue are needed. We have investigated whether sponges fabricated from poly‐L‐lactic acid (PLA) infiltrated with polyvinyl alcohol (PVA) would meet these requirements. Highly porous sponges (porosity = 90–95%) were fabricated from PLA using a particulate leaching technique. To enable even and efficient cell seeding, the devices were infiltrated with the hydrophilic polymer polyvinyl alcohol (PVA). This reduced their contact angle with water from 79 to 23°, but did not inhibit the ability of hepatocytes to adhere to the polymer. Porous sponges of PLA infiltrated with PVA readily absorbed aqueous solutions into 98% of their pore volume, and could be evenly seeded with high densities (5 × 107 cells/mL) of hepatocytes. Hepatocyte‐seeded devices were implanted into the mesentery of laboratory rats, and 6 ± 2 × 105 of the hepatocytes engrafted per sponge. Fibrovascular tissue invaded through the devices' pores, leading to a composite tissue consisting of hepatocytes, blood vessels and fibrous tissue, and the polymer sponge. © 1995 John Wiley & Sons, Inc.
Effect of calcium phosphate (Ca‐P) coatings on trabecular bone response: A histological study
Authors: Caulier H. , van Der Waerden J. P. C. M. , Paquay Y. C. G. J. , Wolke J. G. C. , Kalk W. , Naert I. , Jansen J. A.
Published: December 2004

The trabecular bone response to noncoated and fluorapatite (FA), hydroxyapatite (HA), and hydroxyapatite heattreated (HAHT) plasma‐sprayed coated implants was investigated in a goat animal model. Forty‐eight cylindrical implants were inserted into the trabecular bone of the lateral and medial femoral condyles of twelve goats according to a split plot design. After an implantation period of twelve weeks, the bone‐implant interface was evaluated histologically. Quantitative histomorphometrical measurements demonstrated a significant difference in bone contact between implants inserted in the lateral and medial condyles. In addition, a significant difference in bone apposition was observed between the coated and the uncoated implants. Finally, all Ca‐P coatings showed reduction in coating thickness. Measurements revealed that FA and HAHT showed less reduction in coating thickness than HA coating. Despite the coating reduction, the bone remained in close contact with the implant surface. © 1995 John Wiley & Sons, Inc.
Field emission SEM comparison of four postfixation drying techniques for human dentin
Authors: Perdigao J. , Lambrechts P. , Van Meerbeek B. , Vanherle G. , Lopes A. L. B.
Published: December 2004

Critical‐point drying (CPD) is generally considered essential for the preparation of biologic specimens for electron microscopy. Several attempts have been made to introduce alternative techniques. More recently, this problem has arisen in dentistry, because of the new developments in dentin bonding. The present study focuses on three alternative techniques to CPD: hexamethyldisilzane (HMDS) drying, Peldri II drying, and air drying. Twenty‐four dentin disks were obtained from noncarious extracted human molars by microtome sectioning parallel to the occlusal surface. The dentin surfaces were etched with polymer‐thickened, silica‐free, 10% phosphoric acid semigel, fixed, dehydrated, and dried with one of the four techniques. The specimens were observed in two perpendicular planes, showing dentinal tubules in longitudinal view and crosssection, using a field emission scanning electron microscope. The intertubular demineralized dentin zone was composed of three different successive layers, which did not substantially differ between CPD and Peldri II drying, but were more evident in HMDS‐dried specimens: first, an upper layer of denatured collagen and residual smear layer particles, with sectioned collagen fibrils and few open intertubular pores; second, an intermediate layer of closely packed cross‐sectioned collagen fibers; and third, a deeper layer with unfilled spaces, scattered hydroxyapatite crystals, and few collagen fibers. HMDS drying seemed to preserve better the collagen network and the microporosity of the demineralized dentin surface. Moreover, HMDS drying is easy to perform. The air‐drying method caused some artefacts, such as surface collapsing and thickening of the denatured collagen layer. © 1995 John Wiley & Sons, Inc.