bluuebunny/crossref_metadata_2025_split huggingface dataset:
In vitro degradation of glycine/DL‐lactic acid copolymers
Authors: Helder J. , Dijkstra P. J. , Feijen J. 
Published: December 2004

AbstractThe in vitro degradation of glycine‐DL‐lactic acid copolymers was studied as a function of the composition. These polydepsipeptides were prepared by ring‐opening copolymerization of 6‐methyl‐2,5‐morpholinedione and DL‐lactide. The degradation of discs of the copolymers was performed in a phosphate buffer at pH 7.4 and 37°C. The decrease in molecular weight and weight was determined until complete weight loss had occurred. Poly(DL‐lactide) was used as a reference material. All (co)‐polymers show an immediate decrease in molecular weight, whereas the weight remains almost unchanged during a longer period of time. Decrease in weight started earlier as the glycine content of the copolymer increased. The lactic acid content of the residual material increased during the weight loss showing a higher solubility of polymer fragments with a relatively high content of glycine residues. From the hydrolysis constants it was concluded that the degradation was best described by hydrolysis of ester bonds via a bulk erosion process, autocatalyzed by the generated carboxylic acid end groups. The rate constants varied from 4–7 × 10−2 (day−1) for all (co)polymers. All (co)polymers show an increase in the molecular weight distribution upon weight loss.
Hard tissue replacement (HTR) polymer as an implant material
Authors: Amler M. H. , LeGeros R. Z. 
Published: December 2004

AbstractThis study aimed to evaluate the effectiveness of a synthetic implant material Hard Tissue Replacement polymer (HTR) for: (1) compatibility with bone and soft tissues, (2) capacity to physically attach to bone and soft tissues, and (3) capacity for bone induction and metaplasia. HTR was implanted for a 3‐week test period in femur bones, connective tissue, and skeletal muscle of 15 Sprague‐Dawley descent rats for histological examination and implanted in bone in 6 rats for infrared absorption analyses to determine the presence of new bone. Compatibility (defined as absence of significant inflammation) was present in 13/14 (93%) bone sites, 7/9 (78%) connective tissue, and 4/4 (100%) muscle sites. Physical attachment of HTR occurred in 10/14 (71%) bone sites, 4/9 (44%) connective tissue, and 1/7 (14%) muscle sites. Density of new bone appeared to be greater with HTR than in controls. However, no metaplastic bone was formed in nonbony sites indicating that this material is nonosteogenic. These preliminary findings demonstrated the effectiveness of HTR as an implant material.
Blood compatibility of PEO grafted polyurethane and HEMA/styrene block copolymer surfaces
Authors: Nojiri Chisato , Okano Teruo , Jacobs Harvey A. , Park Ki Dong , Mohammad S. Fazal , Olsen Don B. , Kim Sung Wan 
Published: December 2004

AbstractHEMA/styrene (HEMA/STY) block copolymers and poly(ethylene oxide) 4,000 M.W. (PEO4K) grafted Biomer (B‐PEO4K) surfaces have been synthesized, characterized, and evaluated as blood‐contacting materials. These surfaces have demonstrated improved blood compatibility, compared to Biomer, in in vitro and ex vivo experiments. Biomer vascular grafts (6 mm I.D. 7 cm in length) were fabricated by a dip coating process. The luminal surface was modified either with PEO grafting, HEMA/STY coating, or Biomer coating (control). These surface‐modified grafts were implanted in the abdominal aortas of dogs and evaluated for graft patency and protein adsorption.Surface protein layer thickness was measured by transmission electron microscopy (TEM). B‐PEO4K and Biomer showed thick multilayers of adsorbed proteins (1000–2000 Å) after 3 weeks to 1 month implantation. In contrast, HEMA/STY only showed a monolayer protein thickness (<200 Å), even after 3 months.Visualization of adsorbed plasma proteins (albumin, IgG, and fibrinogen) was performed with scanning electron microscopy (SEM)/TEM using an immunogold double antibody technique. The pattern of protein distribution showed high concentrations of fibrinogen and IgG, and less albumin adsorbed onto Biomer and B‐PEO4K. In contrast, HEMA/STY showed a patchy protein distribution pattern with high concentrations of albumin and IgG, and relatively less fibrinogen.Adsorbed monolayer patterns showed improved compatibility over multilayered proteins. The Biomer and B‐PEO4K grafts occluded within 1 month, while HEMA/STY grafts were patent for over 3 months. The thin and stable adsorbed protein layer on HEMA/STY surfaces may be associated with the microdomain structures of the surface, and will play an important role in long‐term in vivo blood compatibility. This manuscript will evaluate the long‐term in vivo performance of these polymers, analyze the extent of protein adsorption onto the surfaces, and correlate protein layer thickness to the thrombogenicity of the polymer surfaces.
Biochemical changes and cytotoxicity associated with the degradation of polymeric glutaraldehyde derived crosslinks
Authors: Huang‐Lee Lynn L. H. , Cheung David T. , Nimni Marcel E. 
Published: December 2004

AbstractThe reversibility of glutaraldehyde crosslinks has been suggested as a reason for failure of long‐term bioprosthetic implants. The stability of such crosslinks was investigated in tendons and model compounds. Small but cytotoxic levels of glutaraldehyde were still released from crosslinked tendons even after these tendons were extensively rinsed for up to 6 months. The toxic effect was evidenced by the death of fibroblasts surrounding a midsection piece of rinsed crosslinked tendon, while the end section pieces did not show toxic effects. The formation and stability of glutaraldehyde modified [14]‐L‐lysine derivatives were investigated. The polymerization of glutaraldehyde with amino compounds was initially fast but continued to proceed slowly for months. Degradation of high‐molecular‐weight soluble polymers was detected by gel filtration chromatography. Low‐molecular‐weight soluble materials were also released from insoluble products which were formed when high concentrations of glutaraldehyde and radioactive lysine were reacted. These chemical and biological studies suggest that local cytotoxicity of glutaraldehyde crosslinked bioprostheses may be due to unstable glutaraldehyde polymers that persist in the interstices of crosslinked tissues.
Titanium‐coated micromachined grooves of different dimensions affect epithelial and connective‐tissue cells differently in vivo
Authors: Chehroudi B. , Gould T. R. L. , Brunette D. M. 
Published: December 2004

AbstractA desirable feature of an implant surface which penetrates epithelium would be that the surface impedes epithelial downgrowth. Previous experiments have shown that the micromachined, horizontally oriented grooves on the percutaneous implant surface can impede epithelial downgrowth (Chehroudi et al., J. Biomed. Mater. Res., 22, 459 (1988) and 23, 1067 (1989)). However, little is known of the effect of varying groove parameters such as depth, spacing, and orientation on epithelial downgrowth and attachment of epithelial (E)‐cells and fibroblasts (F) to percutaneous implants in vivo. Grooves were produced with a 30‐μm pitch and depths of 22 μm, 10 μm, or 3 μm. In addition, 10‐μm‐ and 3‐μm‐deep grooves were made with pitches of 39 μm and 7 μm, respectively. Implants with grooves oriented either horizontally or vertically to the long axis of the implant as well as smooth control surfaces were coated with 50 nm of titanium and placed in the parietal area of rats for a period of 7 days. Close attachment of E‐cells was found on the smooth, 10‐μm‐ and 3‐μm‐deep, horizontally or vertically aligned grooved surfaces; in contrast, E‐cells bridged over the 22‐μm‐deep, horizontally oriented grooves. F formed a capsule on the smooth surface as well as the 10‐μm‐ and 3‐μm‐deep horizontally oriented grooves, but F inserted obliquely into the 22‐μm‐deep, horizontally aligned grooved surface. Histomorphometric measurements indicated that the epithelial downgrowth was greatest on the vertically oriented grooved and smooth surfaces and was shortest on the 22‐μm‐deep and 10‐μm‐deep horizontally aligned grooved surfaces. These differences indicate that epithelial downgrowth was accelerated on the vertically oriented grooved surfaces and inhibited on the horizontally oriented grooved surfaces. Moreover, the mechanism of inhibition of the epithelial downgrowth may differ among these surfaces. E‐cells bridged over the 22‐μm‐deep grooves and their migration appeared to be inhibited by the F that inserted into the implant surface. In the shallower horizontal grooves, however, epithelial downgrowth was probably inhibited by contact guidance because there was no evidence of F inserting obliquely into the implant surface.
Macromolecular release from collagen monolithic devices
Authors: Gilbert Donna L. , Kim Sung Wan 
Published: December 2004

AbstractCollagen monolithic devices varying in crosslinking density, collagen structure, and crosslinker were fabricated. In vitro release rates of a model macromolecule, inulin, were found to be linear with t1/2 and were affected by crosslinking density, nature of crosslinker, and collagen structure. The biodegradation of the collagen matrix was also examined. Proteolytic enzymes did not degrade the collagen devices; the degradation rate with collagenase was dependent on collagen structure, crosslinker, crosslinking density, and enzyme concentration. In vivo biocompatibility, degradation, and 14C‐inulin release rates were evaluated subcutaneously in rats. After 3 weeks, none of the collagen discs induced any severe cellular response. Dacron® induced a stronger fibroblast response but fewer inflammatory cells as compared to the collgen discs. No significant degradation of the collagen discs occurred within 3 weeks. In vivo release of 14C‐inulin from collagen monolithic devices was diffusion controlled.
Microencapsulation of mammalian cells in a HEMA‐MMA copolymer: Effects on capsule morphology and permeability
Authors: Crooks Colin A. , Douglas Jon A. , Broughton Richard L. , Sefton Michael V. 
Published: December 2004

AbstractA new process for preparing uniform microcapsules with a hydroxyethyl methacrylate‐‐methyl methacrylate copolymer (HEM A‐MMA) has been devised. Capsule diameters were 900‐‐1000 μm in diameter, (± 10–20 μm, ± SD) depending on the precipitation conditions. The process involved the coextrusion of polymer solution (in PEG 200) and the mammalian cell suspension (here erythrocytes) through a needle assembly which is submerged in a layer of hexadecane which is in turn sitting above a stirred isotonic aqueous solution in a volumetric flask. The needle is repeatedly withdrawn from the hexadecane overlayer shearing a droplet from the needle tip which falls into the water, where the solvent is extracted to precipitate the polymer around the cells to yield the capsules. The morphology of the capsule wall was altered by changing the precipitation bath from phosphate buffered saline (PBS) to 0.3 M glycerol. This resulted in greater macroporosity in the wall, presumably because of the faster precipitation due to the higher solvent/precipitant compatibility with 0.3 M glycerol. The permeability to a series of test solutes (glucose, inulin, albumin, and alcohol dehydrogenase, ADH) increased by a factor of ∼ 2, presumably because of the increased macroporosity. Addition of 15% water to the polymer solvent enhanced the macroporosity, presumably by bringing the system closer to the cloud point; however, there was no corresponding increase in permeability. There was a significant decrease in permeability between that of albumin (∼69,000 D) and ADH (∼150,000 D) suggesting that the molecular weight cutoff of these capsules was on the order of 100,000 D as desired. This process is now being evaluated for the encapsulation of pancreatic islets and other cells of potential clinical interest.
The bone–titanium interfacein vitro
Authors: Davies J. E. , Lowenberg B. , Shiga A. 
Published: December 2004

AbstractCommercially pure 5‐mm‐diameter titanium (cpTi) discs received droplet inoculations of cells derived from rat bone marrow and were maintained in supplemented culture medium for 2–3 weeks. The cells and extracellular matrix (ECM) were processed for observation by light (LM), scanning (SEM), and transmission electron (TEM) microscopy. The latter was achieved by freeze‐fracturing the solid metal from the resin‐embedded tissue using a method which preserved the interface. Surface staining of whole discs revealed cells separated from the metal substratum by areas of ECM which stained positively using von Kossa's method to identify mineralization. At SEM, the ECM comprised dense interwoven collagen fiber networks which were partially obscured by globular masses (GMs). Individual GMs were associated with collagen fibers, especially at fiber intersections. EDAX line scan analysis confirmed the presence of Ca and P in these areas which were assumed to be spheritic foci of calcification since the Ca and P peaks diminished in areas which demonstrated only collagen fibers or the underlying cpTi. TEM examination confirmed the presence of globular mineralization and also revealed the presence of an interfacial zone between the metal substratum and the mineralized ECM elaborated by osteoblasts during the culture period. The interfacial zone comprised two layers, a bonding zone containing few collagen fragments and a ruthenium red positive layer containing more densely packed collagen fibers. We believe that this is the first report of both the formation of bonelike tissue on solid titanium substratain vitroand demonstration of an interface which bears close morphological similarities to that known to developin vivo.
The effect of protein and urine on uropathogen adhesion to polymer substrata
Authors: Hawthorn Lesleyann , Reid Gregor 
Published: December 2004

AbstractUropathogenic adhesion was measured using a range of polymer materials with differing surface tension properties. Experiments were carried out in the presence of phosphate buffered saline (controls), Tamm Horsfall protein (THP), and human urine with quantitation by image analysis. The results showed that THP did not bind to the polymer materials and therefore did not act as a receptor surface for type 1 fimbriated Escherichia coli. However, the THP did interfere with adhesion by binding directly to these organisms as well as to Pseudomonas aeruginosa, Staphylococcus epidermidis, and, to a lesser extent, Proteus mirabilis. Incubation of the uropathogens in THP and urine resulted in altered adhesion profiles to polymer surfaces, with no single trend apparent. The results emphasize that fluid components, particularly proteins, and substratum surface tension influence bacterial adhesion to biomaterials.
The effect of fluid shear stress upon cell adhesion to fibronectin‐treated surfaces
Authors: Truskey George A. , Pirone John S. 
Published: December 2004

AbstractCell attachment to and spreading upon a surface is mediated by adhesion molecules, such as fibronectin. The role of fibronectin in maintaining cell adhesion was examined by measuring cell attachment following exposure of cells to laminar flow in a parallel‐plate flow channel. 3T3 fibroblasts were allowed to adhere to glass slides with or without preadsorbed fibronectin for 2 h before exposure to shear stresses ranging from 5 to 140 dyne/cm2. For cells which adhered to glasss surfaces, cell loss was biphasic with a significant loss of cells during the first 2 min of flow, followed by a much slower decline in the number of attached cells with time. Following exposure to shear stresses greater than 5 dyne/cm2, the number of attached cells decreased exponentially as the shear stress increased. The distribution of adhesive stresses among the population of cells was log‐normal with a median of 50 dyne/cm2, a mean of 82 dyne/cm2 and a standard deviation of 108 dyne/cm2. After exposure to flow for 2 h, the adhesive stress of the remaining cells decreased to a mean value of 50 dyne/cm2. Cell adhesion after exposure to flow was increased by preadsorbing fibronectin to the glass surface. The initial loss of cells from fibronectin‐treated glass following exposure to flow correlated with the degree of cell spreading. Preadsorbed fibronectin resulted in a greater number of bonds between the surface and the cell, which in turn promoted cell spreading and increased the adhesive strength of the cell.
In vitro toxicity test of 2‐cyanoacrylate polymers by cell culture method
Authors: Tseng Yin‐Chao , Tabata Yasuhiko , Hyon Suong‐Hyu , Ikada Yoshito 
Published: December 2004

AbstractThe inhibition of Swiss 3T3 cell growth by the microspheres prepared from various 2‐cyanoacrylate polymers was investigated to assess their cell toxicity. Poly(ethoxyethyl 2‐cyanoacrylate) and poly(methyl 2‐cyanoacrylate) microspheres inhibited cell growth in a smaller amount than poly‐(isobutyl 2‐cyanoacrylate) and poly(ethyl 2‐cyanoacrylate) microspheres. The extent of cell growth inhibition by the microspheres decreased with the increasing molecular weight, regardless of the kind of polymers used. Every kind of the microspheres was degraded releasing formaldehyde in the culture medium. The cell growth inhibition by the medium containing the microspheres was observed within 24 h for poly(ethoxyethyl 2‐cyanoacrylate) and poly(methyl 2‐cyanoacrylate). The extent of inhibition was in a linear proportion with the amount of formaldehyde released. It is concluded that the cell toxicity of 2‐cyanoacrylate polymers is attributed to formaldehyde released upon polymer degradation.
Quantitative in vivo studies of hyperemia in the course of the tissue response to biomaterial implantation
Authors: Bouet T. , Schmitt M. , Desuzinges C. , Eloy R. 
Published: December 2004

AbstractHyperemia associated with an inflammatory response has been investigated in rats, by using four different experimental models, i.e., “positive” and “negative” polymer implants from the pharmacopea, operative control, and abscess induced by turpentine oil. 133Xenon clearance, infrared thermography and Laser Doppler Flowmetry (LDF) were used to monitor the subcutaneous local hemodynamic changes from 1 to 40 postoperative days. LDF proved to be a sensitive, reproducible method, able to discriminate positive from negative implants already at the 3rd postoperative day and up to 40 days. This increased local blood flow was also visualized at the site of positive implants at the 14th and 21st postoperative days by means of 133Xe Clearance. Additional information obtained by infrared thermography allowed discrimination between positive implants and control sites but only at the very early stage (1 to 3 days). The significance of the different data collected by the three techniques was correlated with histological events occurring at the different implant sites. LDF may therefore represent a useful technique for noninvasive semiquantitative assessment of tissue response to biomaterials.
Friction properties of the interface between porous‐surfaced metals and tibial cancellous bone
Authors: Rancourt D. , Shirazi‐Adl A. , Drouin G. , Paiement G. 
Published: December 2004

AbstractFriction tests between cancellous bone cubes and porous‐surfaced metal plates were conducted in order to determine the mechanical properties of the interface in a knee porous‐surfaced metal implant. Bone specimens were obtained from fresh frozen amputated tibiae and three metal plates were chosen: titanium bead porous‐surfaced, titanium fiber mesh porous‐surfaced, and smooth stainless steel. Results show that the friction curve is highly nonlinear. Friction coefficients measured vary between 0.3 and 1.3. The friction coefficient of the interface is independent of the excision site of the bone cubes and of the magnitude of the rate of relative displacement at the interface. The friction coefficient appears to vary slightly with the normal contact pressure for all the metal surface. Both porous surfaces have statistically a higher friction coefficient than the smooth surface. This is likely due to the presence of surface asperities whereby the metal ploughs the bone surface. However, no significant difference is observed between bead and fiber mesh types.
A hydrophilic plasma polymerized film composite with potential application as an interface for biomaterials
Authors: Marchant Roger E. , Johnson Steven D. , Schneider Bernard H. , Agger Mary Patricia , Anderson James M. 
Published: December 2004

AbstractA hydrophilic polymer composite film (approx. 420 nm thick), with potential application as an interface for biomaterials has been prepared on nonorganic substrates, which include glass, silicon, and aluminum foil, using a glow discharge plasma polymerization technique. A thin film (110 nm thick) polymerized from hexane provided an adherent protective coating for the substrate material, and covalent bonding sites for the outer layer polymerized fromN‐vinyl‐2‐pyrrolidone. This outer layer provided the hydrophilic surface or interface. The two layers were copolymerized for a short period during transition between monomers to provide an intimate covalently bonded diffuse interphase. Preliminaryin vitroandin vivobiocompatibility studies indicate that the hydrophilic film is non‐cytotoxic, and does not increase the inflammatory response when compared with negative controls.
The effects of bulk versus particulate titanium and cobalt chrome alloy implanted into the rabbit tibia
Authors: Goodman S. B. , Fornasier V. L. , Lee J. , Kei J. 
Published: December 2004

AbstractTwenty‐eight mature New Zealand white female rabbits were allocated into 4 groups of 7 rabbits. Group 1 received a coiled wire of cobalt chrome alloy (Vitallium) (16 gauge × 1 cm). Group 2 received an equal weight of cobalt chrome particles averaging 15.4 μm in diameter. Group 3 received a coiled wire implant of commercially pure (C.P.) titanium (16 gauge × 1 cm). Group 4 received the same weight of C.P. titanium particles averaging 3.8 μm. The implants were placed through a drill hole in the proximal right tibia; the left tibia served as a prepared but nonimplanted control. The animals were killed after 16 weeks and quantitative histology was performed on undecalcified sections of the implant area. Bulk cobalt chrome and titanium implants were surrounded by a thin, incomplete, fibrous tissue layer with decreased numbers of cells. Trabeculae of bone were present within this connective tissue envelope. Fingerlike projections of bone enveloped the implant where it abutted endosteal bone. Clumped and loosely scattered cobalt chrome and titanium particles were surrounded by a minimal amount of fibrous connective tissue. Smaller particles were present within cells. Hematopoietic cells abutted the bulk or particulate implants directly. There was no evidence of acute or chronic inflammation or foreign body reaction. These results should be contrasted with those of Howie et al. in which intraarticular cobalt chrome particles stimulated a rapid proliferation of macrophages and synovial degeneration after 1 week. This may be due to a direct toxic effect of metals in an intra‐articular environment, the smaller particle size used in that study, or to abrasive injury to the hyaline cartilage and subsequent synovitis. Our results underscore the general inert properties of these metals in the short term, when implanted into bone in the sizes and physical forms chosen.