bluuebunny/crossref_metadata_2025_split huggingface dataset:
Albumin‐binding surfaces for implantable devices
Authors: Keogh James R. , Velander Fredrik F. , Eaton John W. 
Published: May 2005

AbstractSurfaces of implantable and blood contact‐devices accumulate adsorbed and denatured proteins. This anomalous layer of proteins may help trigger unwanted events such as activation of coagulation systems and, perhaps, chronic inflammation. Because, in many experimental systems, the purposeful coating of surfaces with albumin will biologically “passivate” materials, we have attempted to develop polymers which, when exposed to blood or body fluids, will spontaneously, selectively, and reversibly adsorb host albumin. We report here a novel derivatization technique for increasing the albumin affinity of implantable polyetherurethane (PU). The technique is based on the incorporation of high‐molecular‐weight dextran to which the albumin‐binding dye Cibacron Blue is covalently attached. Somewhat surprisingly, the amounts of human albumin adsorbed by Blue Dextran‐modified and unmodified PU are quite similar. There are, however, important differences. First, the binding of albumin to derivatized PU is specific and not readily blocked by proteins in albumin‐depleted human serum. Second, the majority of albumin associated with derivatized PU appears to be reversibly bound. Third, the binding of albumin to derivatized PU evidently is mediated primarily through ligandspecific binding of the protein to the albumin‐binding dextran‐dye conjugate. We conclude that it is possible to produce implantable polymers having surfaces which display albumin‐binding dyes that selectively and reversibly bind albumin. Materials with this property, when implanted or exposed to blood, should form an infinitely renewable coating of albumin derived from physiologic fluids. This surface modification strategy may spawn a new generation of implantable materials with improved biologic compatibility.
High‐voltage electron microscopy and conventional transmission electron microscopy of the interface zone between bone and endosteal dental implants
Authors: Steflik D. E. , Sisk A. L. , Parr G. R. , Hanes P. J. , Lake F. , Song M. J. , Brewer P. , McKinney R. V. 
Published: May 2005

AbstractThe interface between mandibular bone and endosteal dental implants was examined with an in vivo dog model. Undecalcified mandibular implant samples were observed with both conventional transmission electron microscopy and highvoltage transmission electron microscopy (HVEM). Results demonstrated the variable nature of the interfacial support tissues. Mineralized bone was often found within 50 nm of the implant surface, separated from that surface only by an electron dense deposit. Osteocytes were observed close to the interface encased within lacunae extending numerous cellular processes through canaliculi. An osteoblast was also observed directly at the interface within a developing lacuna. Other interfacial areas exhibited a finely fibrillar and more electron lucent morphology. Furthermore, other areas were shown to be composed of wider zones of extracellular products containing collagen fibrils, ground substance, and calcified inclusions. Because bone is a n actively growing and remodeling tissue, these different morphological zones around the entire area of the implants would appear to confirm the dynamic tissue response to endosteal dental implants. Further, HVEM stereology was shown to be an exciting research tool to investigate this tissue response.
Bone apposition to plasma‐sprayed cobalt‐chromium alloy
Authors: Luckey Hugh A. , Lamprecht Elden G. , Walt Michael J. 
Published: May 2005

AbstractThe use of porous metallic coatings for fixation of total joint prostheses by bone ingrowth has become a widespread alternative to fixation with PMMA bone cement. However, concerns about such coatings include long‐term effects of metal ion release, potential coating loss, and decreased substrate fatigue strength. The biological fixation capability of a nonporous, high‐integrity plasmasprayed CoCr coating with low surface area was compared to a conventional sintered bead coating in goat cortical and cancellous bone sites after 8 and 16 weeks of implantation. Histological evaluation showed substantial variations in fixation quality between individual animals and between surgical sites with no consistent difference between implant types. Shear testing of bonelimplant interfaces showed that although conventional porous coating exhibited higher overall average shear strengths in cortical bone sites at both time periods, the differences were not statistically significant. In cancellous sites, the average shear strengths achieved with conventional porous and plasmasprayed coatings were essentially equal. Analysis using average paired differences, however, revealed that when porous and plasma‐coated implants are placed in identical sites of contralateral limbs, the plasma coatings consistently yielded higher shear strengths in cancellous bone sites at the later time period. Since current design theory for biological fixation favors metaphysical fixation, this surface may offer potential advantages over conventional porous coatings.
Preparation of dense hydroxylapatite or rhenanite containing bioactive glass composites
Authors: Kangasniemi I. M. O. , de Groot K. , Becht J. G. M. , Yli‐Urpo A. 
Published: May 2005

AbstractThe effect of time at 600°C and of small additions of Al2O3 and B2O3 on the sintering of two composite materials of (1) hydroxylapatite (C ∼I O (P O ∼)∼(O H )∼) and bioactive glass (SiO2‐CaO‐P2O5‐Na2O) or (2) rhenanite (CaNaPO,) and bioactive glass were studied. Scanning microscopy, quantitative EDX, x‐ray diffraction, helium gas density measurements, and diametral measurements were performed on the resulting composites. No reactions were observed with the SEM or XRD between the hydroxylapatite particles and the glass matrix within sufficient sintering times to achieve maximum density. (∼) The rhenanitecontaining composites were observed to form Na2O2CaO3SiO2 crystals by x‐ray diffraction, probably as a result of dissolution of the rhenanite particle surfaces into the glass phase, the crystals formed in the glass or at the interface of the glass, and the ceramic particles. However, within the short sintering times needed to achieve maximum density the rhenanite particles remained mostly intact. The rhenanitecontaining materials gave better results than the hydroxylapatite‐containing materials. The glass composition had a great effect on the densification process.
The effect of lipase on the release of naltrexone from triglyceride‐coated cellulose acetate phthalate microspheres
Authors: Tefft J. A. , Roskos K. V. , Heller J. 
Published: May 2005

AbstractThe ultimate objective of this work is to develop a device that can be triggered by morphine to release naltrexone. In this device, naltrexone is dispersed in cellulose acetate phthalate microspheres which are then spray‐coated with a trilaurin protective coating. The microspheres are contained within a macroporous cylinder which also contains a reversibly inactivated lipase. This enzyme in its inactive state is unable to remove the protective coating but in its active state is able to do so. Inactivation is achieved by the covalent attachment of morphine followed by complexation with a morphine antibody. Triggering is accomplished by the displacement of the lipase‐morphine conjugate from the antibody. In this phase we have investigated the effect of lipase on the release of naltrexone from trilaurincoated microspheres and found that the coated microspheres are stable in a pH 7.4 phosphate buffer at 37°C for at least 1 month, but release 80% of the incorporated naltrexone in one hour when 100 nig of capsules in 5 mL buffer are exposed to 25 μg of lipase.
Effect of soft segment chemistry on the biostability of segmented polyurethanes. II. In vitro hydrolytic degradation and lipod sorption
Authors: Takahara Atsushi , Hergenrother Robert W. , Coury Arthur J. , Cooper Stuart L. 
Published: May 2005

AbstractA series of segmented polyurethanes (SPUs) with various polyol soft segments was prepared and their hydrolytic degradation and degradation due to lipid sorption was investigated. The hydrolytic degradation of the SPUs was investigated in a papain solution, where it was shown that the SPU based on poly(ethy1eneoxide) (PEO) soft segment was susceptible to hydrolytic degradation. X‐ray photoelectron spectroscopic (XPS) data suggest dissociation of the urethane linkage by enzymatic degradation. Degradation by lipid sorption was observed for the SPU based on a poly(dimethylsi1oxane) (PDMS) soft segment. This is ascribed to the high solubility of lipid in the PDMS segment of the SPU.
Bone formation processin porous calcium carbonate and hydroxyapatite
Authors: Ohgushi Hajime , Okumura Motoaki , Yoshikawa Takafumi , Inboue Keisuke , Senpuku Norio , Tamai Susumu , Shors Edwin C. 
Published: May 2005

AbstractThis study determined the bone formation in porous calcium carbonate (CC) and porous hydroxyapatite (HA) in ectopic sites. The bone formation stimulus was derived from bone marrow cells. CC and HA in the shape of disks were implanted with or without rat marrow cells into subcutaneous sites of syngeneic rats. The CC and HA had identical microstructure: pore size was 190–;230 μm, porosity was 50–60% and they were fully interconnected. Bone did not form in any implants without marrow cells (disks themselves), whereas bone consistently formed in the pores of all implants with marrow cells after 4 weeks. The bone formation of both CC and HA occurred initially on surface of the pore regions and progressed toward the center of the pore. Scanning electron microscopy and electronprobe microanalysis revealed a continuum of calcium at the interfaces of both bone/CC and bone/HA implants. These results indicate that the bone formation in calcium carbonate derived from marine corals is comparable to the bioactive hydroxyapatite.
Agarose for a bioartificial pancreas
Authors: Iwata Hiroo , Takagi Tatsuya , Amemiya Hiroshi , Shimizu Hiroshi , Yamashita Kazuya , Kobayashi Kazuo , Akutsu Tessuzo 
Published: May 2005

AbstractIslets were encapsulated into 5% concentration agarose microbeads. The effect of microencapsulation on islet allograft survivals was determined using a streptozotocininduced diabetic (STZ) mouse and a nonobese diabetic (NOD) mouse as recipients. All five STZ BALB/c mice receiving microencapsulated islets (C57BL/6) maintained normoglycemia indefinitely. When NOD mice were used as recipients of the bioartificial pancreas, four of five grafts (islets from C3H/He) functioned for more than 80 d. Two of five NOD mice maintained normoglycemia until animals were sacrificed at 102 and 192 postoperative d. Microbeads made of commercially available agarose can effectively prolong alloislets functioning in the STZ‐diabetic mouse and even in the NOD mouse (animal model of human type I diabetes) without the use of any immunosuppressive drug.
Theoretical analysis on cell size distribution and kinetics of foreign‐body giant cell formation in vivo on polyurethane elastomers
Authors: Zhao Q. H. , Anderson J. M. , Hiltner A. , Lodoen G. A. , Payet C. R. 
Published: May 2005

AbstractThe nature of in vivo leukocyte adhesion and foreign‐body giant cell (FBGC) formation on polyurethanes was studied through theoretical and statistical analyses in terms of cell size distribution, density changes, and kinetics of FBGC formation. The results showed that the size distribution of FBGCs followed a “most probable” distribution. During FBGC formation, the densities of FBGCs changed with time. At an early stage, the number of FBGCs increased with time to a maximum at the expense of macrophages. As more FGBCs were formed and less macrophages were present, the fu‐ sion of FBGCs among themselves became significant. This, in turn, caused a gradual decrease of FBGC density with time. The rate of FBGC formation was characterized by a rate constant that represented certain characteristics of cell fusion and FBGC formation and the density of initial FBGC‐forming macrophages that were a small fraction of leukocytes adhering to the surface. The direct correlations of surface cracking and pitting and adherent FBGCs demonstrated the influence of phagocytic actions of FBGCs on the biostability of implanted polyurethanes. While the cracking was thought to be caused by oxidative degradation facilitated by oxygen ion/radical release of FBGCs, the pitting appeared to result from the Methacrol 2138F aggregates diffusing out of the polymer in an acidic microenvironment under FBGCs, which in turn could be enhanced by the surface degradation and cell phagocytosis. The added Santowhite powder in polyurethane had a significant influence on FBGC formation: It reduced FBGC den‐ sity and rate of FBGC formation by reducing leukocyte adhesion and the number of macrophages participating in FBGC formation.
Biomaterial‐induced alterations of neutrophil superoxide production
Authors: Kaplan S. S. , Basford R. E. , Mora E. , Jeong M. H. , Simmons R. L. 
Published: May 2005

AbstractBecause periprosthetic infection remains a vexing problem for patients receiving implanted devices, we evaluated the effect of several materials on neutrophil free radical production. Human peripheral blood neutrophils were incubated with several sterile, lipopolysaccharide (LPS)‐ free biomaterials used in surgically implantable prosthetic devices: polyurethane, woven dacron, and Velcro. Free radical formation as the superoxide (O2−) anion was evaluated by cytochrome c reduction in neutrophils that were exposed to the materials and then removed and in neutrophils allowed to remain in association with the materials. Neutrophils exposed to polyurethane or woven dacron for 30 or 60 min and then removed consistently exhibited an enhanced release of O2− after simulation via receptor engagement with formyl methionyl‐leucyl‐ phenylalanine. Enhanced reactivity to stimulation via protein kinase C with phorbol myristate acetate, however, was not consistently observed. The cells evalu‐ ated for O2− release during continuous association with the biomaterials showed enhanced metabolic activity during short periods of association (especially with polyurethane and woven dacron). Although O2− release by neutrophils in association with these materials decreased with longer periods of incubation, it was not obliterated. These studies, therefore, show that several commonly used biomaterials activate neutrophils soon after exposure and that this activated state diminishes with prolonged exposure but nevertheless remains measurable. The diminishing level of activity with prolonged exposure, however, suggests that ultimately a depletion of reactivity may occur and may result in increased susceptibility to periprosthetic infection.
Synthesis and nonthrombogenicity of polymer membrane with surface‐graft polymers carrying thrombin inhibitor
Authors: Ito Yoshihiro , Liu Lin‐Shu , Matsuo Ryuichi , Imanishi Yukio 
Published: May 2005

AbstractAn acrylamide derivative of a thrombin inhibitor was synthesized and graft polymerized to the surfaces of polymer mem‐ branes. The thrombin‐inhibitor activity was unaffected by the introduction of an acryloyl group. The surface‐graft membrane deactivated thrombin markedly and suppressed adhesion of platelets, resulting in a high nonthrombogenicity. Immersion of polymer membranes blended with the thrombin inhibitor in phosphate‐buffered saline for 10 d resulted in the loss of nonthrombogenicity, while the polymer membranes grafted with the thrombin inhibitor derivative maintained the non‐thrombogenicity over a long period.
Tissue reactions induced by modified poly(vinyl alcohol) hydrogels in rabbit cornea
Authors: Kobayashi Hisatoshi , Ikada Yoshito , Moritera Takeshi , Ogura Yuichiro , Honda Yoshihito 
Published: May 2005

AbstractThe purpose of this study was to compare the tissue reactions induced by modified poly(vinyl alcohol) (PVA) hydrogels with other materials implanted in the rabbit cornea. PVA hydrogels with and without covalently bonded collagen were compared to ethylene‐vinyl alcohol copolymer, and polysulfone discs. These materials were implanted in the rabbit corneal stroma. The resultant tissue reactions were histologically and clinically studied. The PVA hydrogels had high flux rates of glucose and L‐lactic acid in vitro. Covalent immobilization of collagen onto their surface was found to render them more biocompatible. However, excessive ulceration and vascularization of the cornea still ocurred in vivo, possibly because of extremely little blinking of the rabbits, which might cause desiccation of the cornea. © 1992 John Wiley & Sons, Inc.
Experimental determination of friction characteristics at the trabecular bone/porous‐coated metal interface in cementless implants
Authors: Shirazi‐Adl A. , Dammak M. , Paiement G. 
Published: May 2005

AbstractAn apparatus was developed to measure loaddisplacement friction properties at the cancellous bone/porous‐coated metal plate interface. Bone cubes were obtained from different proximal regions of four resurfaced cadaveric tibiae. Three different poroussurfaced metal plates (one fiber mesh and two bead) and a smooth‐surfaced metal plate were used. In the presence of a constant normal contact pressure (0.10, 0.15, or 0.25 MPa), a variable tangential load up to the maximum resistance of the interface was applied and both relative normal and tangential displacements were recorded. Repetitive and fatigue loadings were also considered. Measured results show that the interface friction curve is highly nonlinear, exhibiting large relative tangential displacements in the range of 50–400 μm before the maximum load is reached. Relative displacements in the normal direction remain below 10 μm. The maximum resistance in friction is independent of the bone excision site, type of porous‐surfaced metal plate, magnitude of normal load, placement of bone cubes on metal plates or vice versa, repetition of applied load, and conservation period of bone cubes in saline solution. The smoothsurfaced metal plate has significantly smaller friction resistance than porous‐coated ones. The fatigue loading of up to 4000 cycles at 1 Hz, in the presence of 0.25 MPa contact pressure, slightly decrease the interface friction coefficient. Finally, the initial secant stiffness of the interface at 75% of the maximum resistance load is found to be larger for the bone cubes from the lateral and medial regions and for the metal plate with smooth surface. © 1993 John Wiley & Sons, Inc.
Cell adhesion onto block copolymer Langmuir‐Blodgett films
Authors: Cho Chong‐Su , Kotaka Tadao , Akaike Toshihiro 
Published: May 2005

AbstractThe 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

AbstractProsthetic 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

AbstractSurface 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.