bluuebunny/crossref_metadata_2025 huggingface dataset:
Cell adhesion onto block copolymer Langmuir‐Blodgett films
Authors: Cho Chong‐Su , Kotaka Tadao , Akaike Toshihiro
Published: May 2005

The attachment of cells onto the surfaces of various block copolymers fabricated either as well‐defined, ordered Langmuir‐Blodgett (LB) films, or solvent cast microphase‐separated structures was studied. In general, more platelets adhered onto the multilayered LB surface than onto microphase‐separated cast surfaces. Scanning electron micrographs of adhered platelets showed extensive morphological changes associated with the LB surface as compared to cast film surfaces. The morphology of adhered hepatocytes was similar for both LB films and cast surfaces. It may be assumed that the surface of a block copolymer LB film does not orient into microdomains, as in the solvent cast surfaces, and only one polymer domain interacts at the interface. © 1993 John Wiley & Sons, Inc.
Application of the quinolone antibiotic ciprofloxacin to dacron utilizing textile dyeing technology
Authors: Phaneuf Matthew D. , Ozaki C. Keith , Bide Martin J. , Quist William C. , Alessi Jean M. , Tannenbaum Gary A. , LoGerfo Frank W.
Published: May 2005

Prosthetic arterial graft infection continues to be a significant and often devastating complication of vascular surgery. The organisms Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis) are the primary pathogens causing acute and late graft infections, respectively.

The objective of this study was to develop an infection‐resistant prosthetic arterial graft by applying the bacteriocidal quinolone antibiotic ciprofloxacin to polyethylene terepthalate (Dacron) via thermofixation (pad/heat), a new application method founded on established textile procedures. We hypothesize that the limited fibrophilic characteristics of ciprofloxacin will permit binding to Dacron and at the same time allow persistent controlled release over an extended period of time. Using pad/heat technology, 33 μg (± 2.97 μg, n = 12) of ciprofloxacin was successfully bound to a 1‐cm2 piece of woven Dacron. A full complement of microbiologic assays demonstrated superior, sustained antistaphylococcal activity of the pad/heat Dacron when compared to Dacron dipped into an equivalent concentration of ciprofloxacin. The sustained antimicrobial efficacy of ciprofloxacin pad/heat‐treated Dacron opens new avenues in the development of infection‐resistant biomaterials based on an understanding of textile chemistry. © 1993 John Wiley & Sons, Inc.
Protein adsorption onto poly(ether urethane ureas) containing methacrol 2138F: A surface‐active amphiphilic additive
Authors: Brunstedt Michael R. , Ziats Nicholas P. , Schubert Mark , Hiltner P. Anne , Anderson James M. , Lodoen Gary A. , Payet C. R.
Published: May 2005

Surface characterization and protein adsorption studies were carried out on a series of additive dispersed and additive coated poly(ether urethane ureas), PEUUs, to characterize early events in the blood compatibility of these materials. A hypothesis that is based on surface hydrophilicity, surface flexibility, and adsorption media has been developed to understand the modulated adsorption of plasma proteins by PEUU additives. Electron spectroscopy for chemical analysis (ESCA) and contact angle analysis were performed on two PEUU formulations as well as on PEUU formulations modified with Methacrol 2138F (co[diisopropylaminoethyl methacrylate (DIPAM)/decyl methacrylate (DM)][3/1]) or acrylate or methacrylate polymer or copolymer analogs of Methacrol 2138F. Methacrol 2138F is a commercially used amphiphilic copolymethacrylate. ESCA showed that the PEUUs. Contact angle analysis also showed that the air side of PEUU formulations loaded with Methacrol 2138F or with its hydrophilic component, homopoly(DIPAM) (h‐(DIPAM)), had a higher percentage of nitrogen at their surfaces than did the base PEUUs. Contact angle analysis also showed that the air side of PEUU formulations loaded with Methacrol 2138F were more hydrophobic than was the air side of base PEUUs when films were cast from dimethylacetamide. However, during contact angle testing, the air side of PEUU films loaded with Methacrol 2138F rapidly became more hydrophilic than did the air side of the base PEUU films. A radioimmunoassay and whole or diluted human plasma were also used to characterize the presence of the proteins fibrinogen, immunoglobulin G, factor VIII/von Willebrand factor, Hageman factor (factor XII), and albumin, on the surface of the same PEUUs as analyzed by ESCA and contact angle. The protein adsorption assay showed that PEUU films loaded or coated with Methacrol 2138F, with a copolyacrylate analog of Methacrol 2138F (co(diisopropylaminoethyl acrylate [DIPAA]/decyl acrylate [DA]) [3/1]), or with the hydrophilic polyacrylate or polymethacrylate component analogs of Methacrol 2138F (h‐DIPAM or h‐DIPAA) adsorbed significantly lower amounts of the proteins than did either the base PEUU formulations or the homopoly(decyl methacrylate) (h‐DM) or homopoly(decyl acrylate) (h‐DA) coated or loaded PEUUs. © 1993 John Wiley & Sons, Inc.
Guided bone tissue elaboration by osteogenic cells in vitro
Authors: Gomi K. , Davies J. E.
Published: May 2005

Primary rat bone marrow cells were cultured for 2 weeks in polystyrene dishes whose surfaces had been roughened using 600‐ or 320‐grit silicon carbide paper. Eight samples were prepared of each of the three groups of dishes, to include a nontreated control suface. Following the culture period, the dishes were stained by von Kossa's method. The distribution of bone formed during the culture period was examined by light microscopy and the area of bone formed quantified. Results demonstrated that both the amount and spatial distribution of bone were influenced by the roughness of the underlying substratum. Differences between the smooth and roughened surfaces were statistically different at P < .05. © 1993 John Wiley & Sons, Inc.
Hydroxylapatite/poly(L‐lactide) composites: An animal study on push‐out strengths and interface histology
Authors: Verheyen C. C. P. M. , de Wijn J. R. , van Blitterswijk C. A. , de Groot K. , Rozing P. M.
Published: May 2005

In the development of new materials for resorbable systems for bone fixation and replacement, composites of hydroxylapatite and poly (L‐lactide) (HA/PLLA) were tested. In a transcortical implantation model in goats the interactions at the bone‐implant interface were studied with post‐operative intervals up to 1 year. Push‐out testing of the implants indicated that PLLA reinforced with 50 wt% hydroxylapatite coating of 50 μm thickness increases interfacial shear strength at 3 months of implantation when compared to unfilled poly(L‐lactide) (P < .01). Scanning electron microscopy showed that the failure mode was predominantly at the coating‐implant interface. Implantation periods longer than 3 months did not result in a significant increase in push‐out strength because of the resorbing PLLA matrix. In support of the above findings there was histological evidence, on a light microscopical level, of increased bone contact at the interface for the composites, HA incorporated in or coated on PLLA, compared to unfilled poly(L‐lactide). © 1993 John Wiley & Sons, Inc.
Patency and blood flow in gas denucleated arterial prostheses
Authors: Vann Richard D. , Ritter Edmond F. , Plunkett Mark D. , Wyble Charles W. , Bensen Christopher V. , Gerth Wayne A. , Barwick William J. , Klitzman Bruce
Published: May 2005

Biomaterials exposed to blood often fail due to thrombosis. Gas nuclei (air) in the material are thrombogenic and a potential cause of failure. The effects of gas nuclei on patency and blood flow were studied in 4 mm diameter arterial grafts (Gore ePTFE; Johnson and Johnson Vitagraft ePTFE; Bard ACG EXS) in the femoropopliteal position of dogs. Control and denucleated (air‐free) grafts were implanted bilaterally. Grafts were denucleated by immersion in degassed saline and exposure to 4 torr vacuum and 3,000–20,000 psig pressure. Graft patency was determined at harvest in 46 dogs. Blood flow was measured with acoustic flow probes in eight dogs. Denucleated graft patency was 60% after 2 days of implant while control patency was 22% (P < .05). Measured blood flow was higher in denucleated grafts than in control grafts (P < .02) in 4 of 5 dogs which had significantly different flows. Patency and flow decreased to zero for both control and denucleated grafts over periods of up to 80 days. Air in the control grafts may have been absorbed within several days, leading to late similarity with the denucleated grafts. Thus, removing the air from 4 mm ePTFE grafts decreased acute thrombosis and increased the patency. © 1993 John Wiley & Sons, Inc.
Strain distribution in the proximal femur with flexible composite and metallic femoral components under axial and torsional loads
Authors: Otani Takuya , Whiteside Leo A. , White Stephen E.
Published: May 2005

This study investigated strain distribution changes in the proximal femur after implantation of a flexible composite femoral component (carbon composite material, modulus of elasticity = 18.6 GPa), a titanium alloy implant (E = 100 GPa), and a stainless steel implant (E = 200 GPa). Transverse as well as longitudinal strain was measured using bipolar strain gauges at eight locations on the proximal femur under both physiologic axial (1000 N and 2000 N) and physiologic torsional (10 N‐m and 20 N‐m) loads. Under axial load, longitudinal compressive strain at the calcar region was significantly greater in intact femurs and the carbon composite stem specimens than in the two metal stem specimens. The difference between intact femurs and the carbon composite stem specimens was not significant. Stress shielding in the proximal lateral region of the femur, however, was still apparent even in the carbon composite stem specimens. Without seating of the stem collar on the femoral neck, longitudinal compressive strain was not generated at the calcar region, and transverse tensile strain at this region was increased. With conventional implant design, the stem collar was still necessary even in the flexible composite stem to provide near normal longitudinal compressive strain in the calcar region. Under torsional load, proximal strain in intact femurs was small and the proximal strain levels observed after either carbon composite or titanium alloy stem implantation were greater than strain levels before implantation. It seemed unlikely that torsional stress relief played a significant role in proximal bone loss after total hip arthroplasty. Both longitudinal and transverse strains at the calcar region under torsional load were significantly greater in the carbon composite stem specimens than in both intact femurs and the titanium alloy stem specimens, suggesting that these abnormally high proximal stresses may cause high proximal micromotion of the implant, and even bone fracture. Proximal implant design seems to be of paramount importance with flexible composite femoral components to avoid excessive proximal stress concentration under torsional load and‐to provide near normal strain distribution in the proximal femur. © 1993 John Wiley & Sons, Inc.
Histologic investigation of the biologic behavior of different hydroxyapatite plasma‐sprayed coatings in rabbits
Authors: Jansen J. A. , van der Waerden J. P. C. M. , Wolke J. G. C.
Published: May 2005

The aim of this study was to investigate bone response to and biostability of three different hydroxyapatite (HA)‐coatings. Therefore, coated and uncoated titanium implants were inserted into the tibia of rabbits. Implantation times were at 3 and 12 weeks. The histological evaluation included measurement of the amount of bone apposition to the various implant surfaces. The results demonstrated at 3 and 12 weeks no marked differences in bony reaction at the cortical level to the different implant materials. However, compared with the 3‐week specimens, at 12 weeks extensive maturation of the woven bone callus had occurred. In addition, all 12‐week implants induced bone formation in the medullary cavity. It was also noted that all HA‐coatings showed loss of coating thickness. Quantitative determination of bone contact demonstrated that all 12‐week implants showed the same high amount of bone apposition. © 1993 John Wiley & Sons, Inc.
Polymethylmethacrylate particles enhance DNA and protein synthesis of human fibroblasts in vitro
Authors: Frondoza Carmelita G. , Tanner Kamaryn T. , Jones Lynne C. , Hungerford David S.
Published: May 2005

Aseptic loosening of polymethylmethacrylate (PMMA) fixed prosthesis is characterized by formation of a radiolucent fibrous membrane, accumulation of inflammatory cells and osteolysis. Since this membrane is produced by fibroblasts, it is likely that these connective tissue cells play a critical role in the loosening process. Whether fibroblasts form the radiolucent membrane in response to stimulation by PMMA has not yet been established, nor is it known whether fibroblasts play a role in attracting inflammatory cells to the bone‐cement interface by secreting chemical mediators. To address this question, we analyzed the in vitro response of normal human fibroblasts to PMMA. Cells were plated with 105/mL Dulbecco minimal essential medium and were incubated 4 h later with PMMA particles, polystyrene (PS) particles, or medium alone. Proliferative capacity monitored by incorporation of 3H‐thymidine was significantly increased following a 48 h exposure to PMMA. Protein synthesis determined by incorporation of 14C‐leucine and 14C‐proline was also increased. In contrast, levels of secreted prostaglandin (PG) E2 assayed immunoenzymatically was not altered by PMMA. Fibroblasts exposed to control PS did not change their proliferative or protein synthetic activity. Fibroblasts internalized PMMA and PS particles without detectable ultrastructural damage. PMMA enhancement of fibroblast proliferative capacity and protein synthetic ability observed in our in vitro assay system suggests similar effects on fibroblasts in vivo. © 1993 John Wiley & Sons, Inc.
Conformational changes of fibronectin induced by polystyrene derivatives with a heparin‐like function
Authors: Stanislawski L. , Serne H. , Stanislawski M. , Jozefowicz M.
Published: May 2005

It was previously reported that polystyrene substituted with the sulfonate group, PSSO3, which has anticoagulant heparin‐like properties, and then coated with fibronectin supports the growth of human umbilical vein endothelial cells. On the other hand, polystyrene substituted with the amino acid sulfamide group, PSSO2‐Asp, which has a higher anticoagulant activity, and then coated with fibronectin no longer supported the growth of endothelial cells. We report here that, while the affinity of fibronectin to either polymer is of the same order of magnitude, fibronectin is adsorbed onto the PSSO2‐Asp polymer in a different conformation compared to the PSSO3 polymer. This was shown by a higher binding of polyclonal antifibronectin antibodies to fibronectin‐coated PSSO2‐Asp polymer, and by a decreased susceptibility of the coated fibronectin to proteolysis by thermolysin. This study provides evidence that a solid phase substrate with a strong heparin‐like function may influence the conformation and biological properties of fibronectin. © 1993 John Wiley & Sons, Inc.
Relationship between arterial thrombosis and neutralization of a polyethylene ionomer
Authors: Goggins Jean A. , Hiltner Anne , Jones Paul K. , Jones Richard D.
Published: May 2005

The influence of three levels of sodium neutralization of an ethylene/ methacrylic acid copolymer on in vivo blood compatibility was studied in a canine arterial model. Effects due to sample fabrication methods (thermal pressing versus solution casting) were also monitored. Sodium content, sodium release, hydrogen dissociation, and localization of anionic groups were noted. Polymer surface energy, surface morphology, water uptake, and thermal properties were characterized.

Material characterization and in vivo implantation disclose the following: (1) Thermal pressing generated oxidation degradation products that decreased in vivo blood compatibility. Solution‐cast samples adhered and activated fewer blood elements. (2) Platelets and leukocytes were sensitive to differences in shear rate in the carotid and femoral arteries, with the femoral site tending toward higher shear, more platelet deposition and fewer leukocytes. (3) The surface properties of the polyethylene control, 0% Na, and 50% Na samples tended to be similar. These properties were different from the 100% Na ionomer was more hydrophilic, had a higher polar component for its surface energy, and was unique in exhibiting discrete ionic clusters 1–10 μm in diameter on its surface. (4) These differences were manifested in vivo by platelet activation and thrombus development on the polyethylene, 0% Na, and 50% Na implants, while the 100% Na implant surfaces were predominantly covered by singly adherent, unactivated platelets. (5) It is proposed that the improvement in biocompatibility for the 100% Na ionomer is due to the cluster development in the neutralized methacrylic component and that either directly, or through appropriate protein adsorption and/or conformational adjustment to the cluster regions, platelets are not activated and do not initiate the coagulation mechanism. © 1993 John Wiley & Sons, Inc.
Analysis of the extractive and hydrolytic behavior of microthane poly(ester‐urethane) foam by high pressure liquid chromatography
Authors: Amin Prafulla , Wille John , Shah Kishore , Kydonieus Agis
Published: May 2005

Microthane foam, a poly(ester‐urethane) (PU) used in the manufacture of Meme/ Replicon breast implants, was analyzed by an HPLC method to determine whether 2,4‐ and 2,6‐toluenediamine (TDA) were formed under a variety of physiological and nonphysiological and nonphysiological extraction and hydrolytic conditions. At our detection limit of 20 ppb, no 2,4‐ or 2,6‐TDA was observed in either methyl tert‐butyl ether (MTBE), or aqueous buffer extracts of PU foam. The predominant extractable components identified by HPLC UV‐analysis, were a mixture of nonaromatic and aromatic PU fragments. Moreover, no detectable amounts of TDA were found in foam or MTBE extract of foam incubated in phosphate buffer, pH 7.4, at 37°C for 5 days. By contrast, 2,4‐ and 2,6‐TDA were found in foam and foam extracts exposed to low concentrations of either strong mineral acid or base; higher levels were found at higher acidity, treatment temperature, or durations of incubation. Moreover, 2,4‐ and 2,6‐TDA were found in oligomers isolated by preparative HPLC and exposed to alkaline conditions. Finally, 1–2 ppm of 2,4‐TDA was detected when PU foam extracts were prepared by the Snyder‐Breder method, which employs acidic and alkaline conditions in the work‐up procedure. Based on these findings, we suggest that published observations of 2,4‐TDA formation from in vitro and ex vivo extractions of PU foam are artifacts resulting from pH effects on oligomeric PU fragments present in or extracted from the foam. © 1993 John Wiley & Sons, Inc.
Incorporation of polylactide–polyglycolide in a cortical defect: Neoosteogenesis in a bone chamber
Authors: Winet H. , Hollinger J. O.
Published: May 2005

One hundred‐micron‐thick threads of 40‐kDa copolymer polylactide : polyglycolide (PLGA) in a 50 : 50 molar ratio in bone chambers were implanted in rabbit tibias. Weekly intravital microscopic observations were used to assess trabecular ingrowth and PLGA absorption, processes referred to as incorporation. Nineteen rabbits were observed from the 3rd (W3) to the 10th or 12th (W10/W12) week postimplantation. Analysis of digitally processed video images obtained weekly showed that PLGA absorption was completed in about 8–10 weeks and trabecular ingrowth delayed to about 1 week slower than its control value. Four of the bone chambers showed PLGA unraveled by week 3, no trabecular ingrowth, and significantly reduced neovascularization. No such apparent inhibitory effects were observed in bone chambers that displayed PLGA absorption. No causal link could be established between the rate of neoosteogenesis and the rate of PLGA absorption, but it was clear that incorporation slowed and rapid degradation inhibited bone regeneration. It was concluded that copolymer synthesis and postsynthesis processing must result in a synthetic with a predictable micro‐ and macro‐molecular structure before one can predict its incorporability in a given reconstruction or fixation site. © 1993 John Wiley & Sons, Inc.
Mechanical and histological evaluation of amorphous calcium phosphate and poorly crystallized hydroxyapatite coatings on titanium implants
Authors: Maxian Suzanne H. , Zawadsky Joseph P. , Dunn Michael G.
Published: May 2005

The effect of amorphous calcium phosphate (Ca/P) and poorly crystallized (60% crystalline) hydroxyapatite (HA) coatings on bone fixation to “smooth” and “rough” (Ti‐6Al–4V powder sprayed) titanium‐6Al‐4V (Ti) implants was investigated. Implants were evaluated histologically, mechanically, and by scanning electron microscopy (SEM) after 4 and 12 weeks of implantation in a rabbit transcortical femoral model. Histological evaluation of amorphous vs. poorly crystallized HA coatings showed significant differences in bone apposition (for rough‐coated implants only) and coating resorption (for smooth‐ and rough‐coated implants) that were increased within cortical compared to cancellous bone. The poorly crystallized HA coatings showed most degradation and least bone apposition. Mechanical evaluation, however, showed no significant differences in push‐out shear strengths between the two types of coatings evaluated. Differences between 4 and 12 weeks were significant for coating resorption and push‐out shear strength but not for bone apposition. Significant enhancement in interfacial shear strengths for bioceramic coated as compared to uncoated implants were seen for smooth‐surfaced implants (3.5–5 times greater) but not for rough‐surfaced implants at 4 and 12 weeks. Rough implants showed greater mean interfacial strengths than uncoated smooth implants at 4 and 12 weeks (seven times greater) and to coated smooth implants at 12 weeks only (two times greater). Mechanical failure of the bone/coating/implant interface consistently occurred within the bone, even in the case of the poorly crystallized HA coatings, which had almost completely resorbed on rough implants. These results suggest that once early osteointegration is achieved biodegradation of a bioactive coating should not be detrimental to the bone/coating/implant fixation. © 1993 John Wiley & Sons, Inc.
Effect of polyol type on the surface structure of sulfonate‐containing polyurethanes
Authors: Silver James H. , Lewis Ken B. , Ratner Buddy D. , Cooper Stuart L.
Published: May 2005

Polyurethanes based upon polytetramethylene oxide (PTMO) as the polyol and derivatized with propyl sulfonate functionality pendant from the urethane nitrogen have previously been shown to possess good bloodcontacting properties. Other investigators have shown that sulfonated polyurethanes containing polyethylene oxide (PEO) as the soft segment are much more thrombogenic than those containing PTMO as the soft segment. In this article, the surface properties of sulfonated polyurethanes based upon either PTMO or PEO are compared. Dynamic contact angle measurements show a significant decrease in the receding angles of the sulfonated PTMO‐containing polyurethane as compared to its nonsulfonated precursor polymer. No significant difference is seen between the receding contact angles of either the sulfonated PEO‐based polyurethane or its nonsulfonated analog. Variableangle electron spectroscopy for chemical analysis (ESCA) studies of sulfonated PTMO‐based polyurethane performed at room temperature show that there is a significant decrease in sulfur content at the surface. In contrast, the sulfonated PEO‐based polyurethane showed little change in sulfur content with take‐off angle. Finally, ESCA studies of freeze‐dried surfaces show a significant increase in sulfur near the surface of the sulfonated PTMO‐based polymer as compared to vacuum‐dried samples but show no such increase for the sulfonated PEO‐based polyurethane. It is suggested that the ability of the sulfonate functionality to be expressed at the surface may explain the observed differences in blood compatibility between the sulfonated polyurethanes based upon polyols of varying hydrophilicity. © 1993 John Wiley & Sons, Inc.
In vitro study on the integrity of a hydroxylapatite coating when challenged with staphylococci
Authors: Verheyen C C. P. M. , Dhert W. J. A. , Petit P. L. C. , Rozing P. M. , de Groot K.
Published: May 2005

An in vitro study was performed to evaluate the effect of Staphylococcus aureus and Staphylococcus epidermidis on the integrity of a hydroxylapatite coating. The coating plasmasprayed on poly(L‐lactide), showed dissolution during a 24 h incubation period. This was indicated by an increase in pH and calcium release in the buffer solution., After 4 h of incubation, calcium levels decreased due to the precipitation of calcium phosphate complexes on the coating. The bacteria digested or dissolved the coating, creating irregularly shaped holes. Although the integrity of the hydroxylapatite coating was focally damaged within 2–4 h of incubation with staphylococci, the extent of the damage was only marginal. Due to the formation of a layer of CaP precipitates though, bacteria could not be counted accurately after 4–8 h of incubation. This model could reveal part of the failure mechanism of infected hydroxylapatite coated implants. © 1993 John Wiley & Sons, Inc.
Particle microelectrophoresis of calcium‐deficient hydroxyapatite: Solution composition and kinetic effects
Authors: Kowalchuk Roman M. , Pollack Solomon R. , Ducheyne Paul , King Linda A.
Published: May 2005

Concurrent work demonstrates that the zeta potential of bone is multivalued and systematically alterable by changes in sample preparation, steeping fluid composition, and steeping time. Since bone mineral is a mixture of carbonated calcium‐deficient hydroxyapatites, and since the zeta potential of calcium‐deficient hydroxyapatite (CDHA) is altered by pH and time in HNO3‐KOH solutions, the zeta potential of CDHA in physiologic Neuman's fluid (NF) compared with that seen in bone could reveal important information on the contribution of the mineral phase to the zeta potential of bone. In addition, such information may be valuable in designing and evaluating calcium‐phosphate ceramics for increased bone ingrowth. Results demonstrate that the zeta potential of CDHA in NF is negative. With increasing calcium in NF, the zeta potential magnitude of CDHA decreases and inverts to positive values given sufficient calcium concentration and steeping time. This result is opposite to that seen in bone, suggesting that exposed CDHA is not the predominant bone microsurface and implicating a bone surface protein component. With increasing phosphate in NF, the zeta potential magnitude increases to more negative values. While low concentrations of fluoride showed no effect, the possibility of an effect with higher concentrations is still to be determined. © 1993 John Wiley & Sons, Inc.
Elastomeric polytetrapeptide matrices: Hydrophobicity dependence of cell attachment from adhesive (GGIP)n to nonadhesive (GGAP)n even in serum
Authors: Nicol Alastair , Channe Gowda D. , Parker Timothy M. , Urry Dan W.
Published: May 2005

The cross‐linked polytetrapeptide matrices based on the repeating amino acid sequences, GGAP, GGVP and GGIP, were prepared and tested for cell adhesion promoting activity in both the absence and presence of fetal bovine serum. For comparison, X20‐poly(GVGVP), a matrix previously shown to be a poor support for cell attachment and spreading, was included. In the absence of serum, all three polytetrapeptide‐based matrices and the polypentapeptide‐based matrix were negative for the adhesion of fibroblasts and endothelial cells. In the presence of serum, various sub‐maximal levels of cell adhesion were found for all matrices except for the matrix based on GGAP. An apparent correlation was noted between the degree of cell attachment to the different polytetrapeptide‐based matrices and the hydrophobicity of those matrices where increased hydrophobicity results in increased cell attachment. The property of being refractory to ligamentum nuchae fibroblast and human umbilical vein endothelial cell adhesion in the presence of serum indicates a potential use for X20‐poly(GGAP) in the development of, for example, additional physical barriers for the prevention of post‐surgical and post‐trauma adhesions. © 1993 John Wiley & Sons, Inc.
In vivo evaluation of protein adsorption to sterically stabilised colloidal carriers
Authors: Norman Maria E. , Williams Paul , Illum Lisbeth
Published: May 2005

A diffusion chamber implanted intraperitoneally in the rabbit was employed as an in vivo model to evaluate the interaction of peritoneal proteins with block copolymer (poloxamer and poloxamine)‐coated polystyrene microspheres (PS). Using a desorption technique followed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis, six proteins of 94, 86, 66, 53, 40, and 20 kDa were desorbed from the carrier systems after incubation with peritoneal fluid in vitro. The 40‐ and 20‐kDa proteins dominated the protein profile. A similar pattern was observed when proteins were desorbed from PS microspheres removed after 24‐h implantation in chambers in the peritoneal cavity, although the protein profile was dominated by the 94‐ and 53‐kDa proteins. In general, coating of PS with block copolymers reduced the amount of protein bound to the microspheres in vitro and in vivo but did not change the types of proteins bound. © 1993 John Wiley & Sons, Inc.
Porous collagen sponge for esophageal replacement
Authors: Natsume Tohru , Ike Osamu , Okada Toshiyuki , Takimoto Nobuyuki , Shimizu Yasuhiko , Ikada Yoshito
Published: May 2005

A new artificial esophagus with a bilayered structure made of porous collagen sponge and silicone was studied. The concept of this study was not to replace an esophageal defect permanently with prosthesis but to promote tissue regeneration by collagen. Five centimeters of cervical esophagus were replaced by this artificial esophagus in 19 adult mongrel dogs. Two weeks after implantation, the collagen sponge was replaced by autologous tissue and regeneration of the “neoesophagus” was observed in all animals. The inner surface of the neoesophagus was covered with mature mucosal epithelium similar to the intact esophagus 4–5 weeks after implantation. The replacement site was not complicated by infection, anastomotic leakage, or exuberant granulation tissue development on the luminal surface. In a long‐term survival study, animals showed moderategrade stenosis but could take normal feed orally and with no clinical problems observed. © 1993 John Wiley & Sons, Inc.
Gentamicin sulfate attachment and release from anodized Ti‐6Al‐4V orthopedic materials
Authors: Dunn D. S. , Raghavan S. , Volz R. G.
Published: May 2005

A novel method has been developed to attach, retain, and release antibiotics from titanium based materials. This technique consists of forming porous surface coatings by anodizing and using the surface chemical properties of the oxide coatings to attach antibiotics. Coatings with pores in the size range 0.1–0.5 μm have been formed in acid solutions. The attachment and retainment of gentamicin sulfate, a cationic antibiotic, to the coatings has been investigated using microbiological methods. In vitro test results have shown that the duration of antimicrobial activity on the surface of anodized materials is dependent on the porosity and isoelectric point of the coatings. Using microporous oxide coatings formed in phosphoric acid solutions, it has been found that antimicrobial activity could be retained for more than 2 weeks. © 1993 John Wiley & Sons, Inc.
Use of polyphosphazenes for skeletal tissue regeneration
Authors: Laurencin Cato T. , Norman Maria E. , Elgendy Hoda M. , El‐Amin Saadiq F. , Allcock Harry R. , Pucher Shawn R. , Ambrosio Archel A.
Published: May 2005

The hydrolytically unstable polyphosphazenes, poly [(imidazolyl) (methylphenoxy) phosphazenes] and poly [ethyl (glycinato) (methylphenoxy) phosphazenes], were studied as potential polymeric supports for cells in tissue regeneration. For bone repair, their specific function would be to support osteoblast growth, forming a bone–polymer matrix. MC3T3–E1 cells (an osteogenic cell line) were seeded onto polymer matrices and cell adhesion and growth as well as polymer degradation were examined. Both imidazoly‐ and ethyl glycinato‐substituted polyphosphazenes supported the growth of MC3T3–E1 cells. An increase in the content of the imidazolyl side group resulted in a reduction in cell attachment and growth on the polymer surface and an increase in the rate of degradation of the polymer. In contrast, substitution with the ethyl glycinato group favored increased cell adhesion and growth and also an increase in the rate of degradation of the polymers. Thus, the polyphosphazenes represent a system whereby cell growth and degradation can be modulated by varying the nature of the hydrolytically unstable side chain. This in vitro evaluation suggests that the polyphosphazenes may be suitable candidate biomaterials for the construction of a cell–polymer matrix for tissue regeneration. © 1993 John Wiley & Sons, Inc.
Polyvinyl alcohol plasma deposited nylon 4 membrane for hemodialysis
Authors: Shih C. Y. , Lai J. Y.
Published: May 2005

Polyvinyl alcohol (PVA) is a hydrophilic and blood compatible material, but it is easily hydrolyzed in aqueous solution. Various methods, including chemical crosslinking and γ‐ray irradiation, have been investigated by many researchers for overcoming the instability of PVA in aqueous solution. This study suggests a new hemodialysis membrane, which is prepared by plasma depositing vinylacetate (VAc) onto annealled nylon 4 membrane, followed by hydrolysis treatment. This improves the blood compatibility of nylon 4 and overcomes the hydrolysis problem of PVA. In addition to conventional plasma deposition, the plasma initiated interpenetrating network (IPN) method is also investigated.

The new hemodialysis membranes prepared by both conventional plasma deposited VAc onto nylon 4 (PPVA/N4) and IPN polymer of plasma initiated VAc onto nylon 4 (PIPVA/N4 IPN) show significant improvement in blood compatibility. However, the solute permeabilities of PIPVA/N4 IPN membranes are higher than those of PPVA/N4 membranes. The permeabilities of NaCl, vitamin B12, and albumin for membranes prepared by IPN at 80 W, 30 sec plasma deposited conditions, i.e., the optimized conditions, are 3.614, 0.070, and 0.000 × 10−5 cm2/min, respectively. The mole ratio of adsorbed fibrinogen to adsorbed albumin (the mole ratio F/A) for this membrane is 0.20, and it also shows excellent blood compatibility in this study. © 1993 John Wiley & Sons, Inc.
Adsorption/desorption of human serum albumin at the surface of poly(lactic acid) nanoparticles prepared by a solvent evaporation process
Authors: Verrecchia T. , Huve P. , Bazile D. , Veillard M. , Spenlehauer G. , Couvreur P.
Published: May 2005

Biocompatible and biodegradable nanoparticles of poly‐(lactic acid) 100% L‐lactic units = PLA) were prepared by an emulsion, microfluidization, and solvent evaporation method using human serum albumin (HSA) as a surface agent. A radiolabeling technique was employed to quantify the serum albumin bound to the nanoparticles and to measure its desorption kinetics in various media at 22°C and 37°C (Phosphate buffer pH 7.4, serum albumin 40 g/L in phosphate buffer pH 7.4 and fetal calf serum). The amount of serum albumin bound to the nanoparticles was found to be a linear fur ction of 1/D (where D is the nanoparticle mean diameter) and was related to the total developed area of the nanoparticles. The adsorption/desorption behavior of serum albumin at the surface of the nanoparticles suggested a multilayer adsorption model. Moreover, a part of the serum albumin molecules was irreversibly bound regardless of the incubation conditions. Consequently, the classical Langmuirian theories of equilibria could not be applied. © 1993 John Wiley & Sons, Inc.
Dacron vascular biomaterial triggers macrophage ectoenzyme activity without change in cell membrane fluidity
Authors: Chignier Elza , Guidollet Jeanine , Freyria Anne Marie , Ardail Dominique , McGregor John Louis , Louisot Pierre
Published: May 2005

Biomaterials induce an inflammatory reaction characterized by a rapid recruitment at the implantation site of polymorphonuclear cells and macrophages. In the course of the inflammatory response, the cellular activation triggers expression of a number of enzymes, such as 5′‐nucleotidase, which is widely distributed in animal cell membranes as an ectoenzyme. It is now well established that 5′‐nucleotidase activity decreses following the contact of inflammatory cells with foreign particles. In this paper we investigate a possible correlation between the enzymatic activities and the dynamic properties of the cell membrane bilayer. Dacron pieces were introduced into rats' peritoneal cavities for a period of 6 h, after which the peritoneal cells were harvested, and various enzyme assays performed, including those for cytoplasmic, lysosomal, and ectoenzymes. In parallel, we studied cell membrane fluidity, using fluorescence polarization of 1‐(4‐trimethylammoniumphenyl)‐6‐phenyl‐1,3,5‐hexatriene (TMA‐DPH), and cellular ultrastructural alteration resulting from the cell‐biomaterial interactions using scanning and transmission electron microscopy. Our results show that: (1) macrophages spread around the Dacron fibers with cytoplasmic finger‐like projections, but no phagolysosomes, (2) 5′‐nucleotidase levels decrease with surgical trauma in comparison with the resident cell exudate, (3) implantation of biomaterials slightly modify the 5′‐nucleotidase levels observed in the sham animal, (4) no differences in the anisotropy values indicating that membrane lipid order within the cells could not account for the observed decrease of 5′‐nucleotidase activity. Thus, we can suggest that 5′‐nucleotidase expression may reflect a particular feature of cell activation without a phagocytic process. © 1993 John Wiley & Sons, Inc.
Comparison of human and canine external femoral morphologies in the context of total hip replacement
Authors: Bloebaum Roy D. , Ota Doug T. , Skedros John G. , Mantas John P.
Published: May 2005

The canine is frequently used as a model for human hip arthroplasty research. In order to better understand the appropriateness of the canine as a model for human total hip replacement studies, the external morphology of canine and human femurs were examined and compared. Several differences were found between canine and human femora, including angular measurements, anterior bow, and femoral head position relative to the femoral diaphysis. In addition, the human femur was noted to undergo age‐related changes in several of the measured parameters. The canine femur did not exhibit any age‐related changes in the measured parameters. This study suggests that there are limitations to the use of the canine model in human hip arthroplasty research, and that discretion must be exercised when attempting to extrapolate results from a canine study to the human clinical condition. © 1993 John Wiley & Sons, Inc.
Tumorigenicity of poly‐L‐lactide (PLLA) plates compared with medical‐grade polyethylene
Authors: Nakamura Tatsuo , Shimizu Yasuhiko , Okumura Norihito , Matsui Teruo , Hyon Suong‐Hyu , Shimamoto Takeshi
Published: May 2005

Poly‐L‐lactide (PLLA) plates, 20 × 10 × 1 mm in size, with flat surfaces, were implanted into 50 young male Wistar rats subcutaneously, and the incidence of tumors for 2 years under specific pathogen‐free (SPF) conditions was evaluated. Tumors arose in 22 rats (at the implant sites in 20, and distant from the implantation site in 2). As a control, plates of medical‐grade polyethylene of the same shape were implanted into 50 rats. Tumors appeared in 23 of these rats (21 at the sites of the plates, and 2 ectopically). In 30 rats given sham operations, no tumors appeared in the 2 year observation period. Histologically, all the tumors were mesenchymal malignant tumors resembling fibrosarcoma or malignant fibrous histocytoma (MFH) in humans. In 6 of the PLLA tumors and 3 of the PE tumors, bone formation was observed. There was no significant difference between the incidence of tumors caused by PLLA plates and that of tumors caused by medical‐grade polyethylene plates. Macroscopically, PLLA plates retained their initial shape for 2 years. Scanning electron microscopy revealed small holes on the surfaces of the plates, and their molecular weight was reduced to 8% of the initial value. © 1994 John Wiley & Sons, Inc.
The formation of hydroxyapatite‐gelatin composites at 38°C
Authors: TenHuisen Kevor S. , Brown Paul W.
Published: May 2005

Composites comprised of calcium deficient hydroxyapatite (CA/P = 1.5) and gelatin form in about 4 h at 38°C. The solid reactants used are CaHPO4 and Ca4(PO4)2O and the liquid reactant is gelatin solution. The reaction forming hydroxyapatite occurs in several steps. Based on the measurement of heat liberation, there is an initial period where the reaction rate is low. This is followed by a period of constant reaction until the reaction is complete. Analysis of the variation in pH shows that hydroxyapatite formation occurs at a steady state pH near 8.2. Analyses of the evolution of crystalline phases indicates that Ca4(PO4)2O is consumed prior to complete reaction resulting in a phase assemblage of hydroxyapatite (CA/P > 1.5) and CaHPO4. Further reaction results in compositional adjustments in hydroxyapatite as CaHPO4 is consumed. Microstructurally, the composites which form consist of clusters of hydroxyapatite embedded in a gelatin network. The presence of gelatin does not influence the morphology of the hydroxyapatite which forms nor does it retard its rate of formation. © 1994 John Wiley & Sons, Inc.
Physicochemical properties of calcific deposits isolated from porcine bioprosthetic heart valves removed from patients following 2–13 years function
Authors: Tomazic B. B. , Brown W. E. , Schoen F. J.
Published: May 2005

The purpose of this study was to characterize the physicochemical properties of calcific deposits that cause the failure of tissue‐derived heart valve bioprostheses. This was done in an effort to understand the mechanism of pathologic biomineralization in the cardiovascular system and potentially prevent deterioration of bioprostheses. Calcific deposits taken from 10 failed bioprosthetic valves that had been implanted in patients for 2–13 years were characterized by chemical analysis, x‐ray diffraction, FTIR spectroscopy, scanning electron microscopy, polarized light microscopy, and solubility measurements. The combined results identified the biomineral as an apatitic calcium phosphate salt with substantial incorporation of sodium, magnesium and carbonate. The average Ca/PO4 ratio for this “young” pathologic biomineral was ∼1.3, considerably lower than ∼1.7 found in mature atherosclerotic plaque biomineral and mature skeletal biomineral, both of which approximate hydroxyapatite in composition. Deproteinated calcific deposits from bioprostheses had thermodynamic solubilities comparable to those of both atherosclerotic plaque, typical pathologic biomineral and hydrolyzed octacalcium phosphate (OCP, Ca4H(PO4)3 · 2.5 H2O), a proposed precursor phase to biomineral apatite. This later finding, together with chemical composition and structrual details of the bioprostetic deposits themselves, supports a mechanism of cardiovascular calcification in which OCP plays a crucial role in the formation of the final apatitic phase. This suggests an approach toward prevention of bioprosthetic tissue calcification through control of the formation of the kinetically favored OCP precursor and/or its transformation into bioapatite. © 1994 John Wiley & Sons, Inc.

This article is a U.S. Government work and, as such, is in the public domain in the United States of America.
Anisotropic elasticity and strength of glutaraldehyde fixed bovine pericardium for use in pericardial bioprosthetic valves
Authors: Zioupos P. , Barbenel J. C. , Fisher J.
Published: May 2005

Uniaxial tensile tests were performed on glutaraldehyde fixed bovine pericardial strips prepared from chemically modified pericardial samples. These samples originated from an area which demonstrated anisotropic mechanical properties in the native material and which is suitable for the construction of leaflets for pericardial bioprostheses. After glutaraldehyde fixation the tissue had retained its anisotropicity in stiffness and strength in two orthogonal directions. In the range of the functional stresses for a heart valve leaflet (> 1 MPa) the unconstrained fixation regime had modified the initial anisotropic elastic behavior into a more isotropic one. The implications of these findings are that leaflets manufactured from bovine pericardium can be made to resemble, to a degree, the well known anisotropy found in two orthogonal direction in natural human heart valve leaflets, or porcine bioprosthetic heart valve leaflets. © 1994 John Wiley & Sons, Inc.
Calcium phosphate precipitation on the surface of HA‐G‐Ti composite under physiologic conditions
Authors: Ban S. , Maruno S. , Iwata H. , Itoh H.
Published: May 2005

Hydroxyapatite‐glass‐titanium (HA‐G‐Ti) functionally gradient composite plates bound face‐to‐face by nylon wire were soaked in a simulated body fluid. The gap between the plates was filled with the precipitates after soaking for 6 months, and a tight chemical bond was formed between them. Field emission‐type (FE) scanning electron microscopy (SEM) and transmission electron microscopy observations revealed that the growth rate and morphology of the precipitates differed widely from the outside portion to the inside one on the surface region of the composite plates. In the portion relatively near the outside, the mutually bonded portion, needle‐like precipitates with preferred orientation to the c‐axis were markedly observed. From the results of Fourier transform infrared spectroscopy and energy dispersive x‐ray microanalysis, it was found that the precipitates were Ca‐deficient carbonate apatite with low crystallinity. On the other hand, HA‐G‐Ti composite rods were implanted in the femur of beagle dogs for 3 months. FE‐SEM observations demonstrated that needle‐like precipitates were deposited on both the surfaces of the composite and bone at the portion having a narrow gap, about 0.1–0.2 mm between them prepared deliberately before implantation. It was found that both the morphologies and the composition of the precipitates in vivo were similar to those in vitro. It is concluded that the HA particles on the surface of the composite act as nucleation sites for precipitation in physiologic environments, whereas the glass matrix is independent to it. © 1994 John Wiley & Sons, Inc.