bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of the acyl azide method for cross‐linking collagen‐rich tissues such as pericardium
Authors: Petite H. , Rault I. , Huc A. , Menasche Ph. , Herbage D. 
Published: December 2004

AbstractCollagen biomaterials should be cross‐linked in order to prevent biodegradation when they are used as implants. We have compared the cross‐linking efficiencies of glutaraldehyde and acyl azide in pericardium. Glutaraldehyde is used currently, but it elicits a cytotoxic effect which reduces the biocompatibility of cross‐linked tissue. We have attempted to overcome this problem by developing a cross‐linking method that obviates incorporation of foreign agents. Our process involves transformation of free carboxyl groups on collagen into acyl azide groups, which react with free amino groups on adjacent side chains. We have shown that the greatest increase in the thermal stability of collagen, as measured by differential scanning calorimetry, is achieved when tissue swelling is inhibited by the addition of sodium chloride (1 M) during acyl azide formation. Under these conditions, the denaturation temperature (Td) of pericardial collagen treated with acyl azide is raised to 83.4°C and that of tissue treated with glutaraldehyde to 85.1°C. Moreover, acyl‐azide‐treated tissues have the same resistance as glutaraldehydetreated tissues to chemical solubilization by cyanogen bromide and to enzymatic digestion by collagenase.
In vitro biocompatibility of polyetheretherketone and polysulfone composites
Authors: Wenz L. M. , Merritt K. , Brown S. A. , Moet A. , Steffee A. D. 
Published: December 2004

AbstractShort carbon fiber reinforced composites could potentially replace some of the metal alloys used in orthopedic implants. In particular, polysulfone and, more recently, polyetheretherketone have been considered as the matrix material for carbon fiber reinforced composite implant materials. ASTM standards F813 and F619 for direct contact cell culture evaluation and extraction were employed to determine the in vitro biocompatibility of a carbon fiber composite of polyetheretherketone, PEEK, in comparison to a carbon fiber reinforced polysulfone composite. The cell cultures were assessed qualitatively by microscopy and quantitatively using an enzyme assay to determine cytotoxicity. Overall, the cellular response to the PEEK and polysulfone composites were negligible indicating that further in vivo studies with these materials are appropriate.
Cytotoxicity testing of wound dressings using normal human keratinocytes in culture
Authors: Rosdy Martin , Clauss Louis‐Christian 
Published: December 2004

AbstractComparative cytotoxicity testing of 16 wound dressings of different composition show that normal human keratinocytes (NHK) growing on a fibroblastic feeder layer are as sensitive to toxic materials by direct contact as the confluent MRC5 fibroblasts used for standard cell culture cytotoxicity testing, and slightly more sensitive when extracts of the dressings were tested. After direct contact with each of the cell types, we found effects due to 12 dressing samples (75%), but the extracts of only 6 of them induced changes in cell shape or cell death on NHK, and 4 of them on MRC5 cells. In order to assess the compatibility of these dressings with a pure population of epidermal cells, the cell type responsible for reepidermization of healing wounds, we then tested the sensitivity, both to dressing samples and extracts, of normal human keratinocytes (NHK) grown in chemically defined medium and without a feeder layer: The results show epidermal cytocompatibility of 10 dressing extracts, while 6 others induced cytopathic effects. Three of these extracts specifically damaged epidermal cells and inhibited their proliferation. When comparing the sensitivities of NHK (in defined medium) and MRC5 cells, we observed complete correlation for 75% of the dressings by extract testing and in 94% of the cases after direct contact.
Poly(dimethylsiloxane)‐poly(ethylene oxide)‐heparin block copolymers II: Surface characterization and in vitro assessments
Authors: Grainger D. W. , Knutson K. , Kim S. W. , Feijen J. 
Published: December 2004

AbstractAmphiphilic block copolymers containing poly(dimethylsiloxane), poly(ethylene oxide), as well as heparin‐coated glass beads and tubes were evaluated for the amounts and activities of surface‐immobilized heparin. Because the amphiphilic copolymer system is thermodynanmcally predicted to demonstrate low‐energy phase enrichment on the surfaces of aircast films, studies were also undertaken to understand the in vitro results. Solvent‐cast copolymer films have a heterogeneous microphase‐separated structure according to transmission electron micrographs. Wilhelmy plate contact angle analysis indicates significant surface restructuring occurs upon hydration. Attenuated total reflectance infrared spectroscopy studies of the desiccated and hydrated films at two different sampling depths show compositional heterogeneity as a function of depth, as well as near surface restructuring allowing surface enrichment of the high‐energy segments following contact with water. Significant concentrations of heparin are detected on the surface of these coatings by toluidine blue assays. In addition, a portion of the surface‐bound heparin maintains its original bioactivity as determined by recalification times, thrombin times, and Factor Xa assays. These substrates were also tested for platelet adhesion and activation reactions in vitro using polymer‐coated beads in rabbit platelet‐rich plasma. Heparinized polymers promoted low levels of platelet adhesion and serotonin release. Surface concentrations of heparin from bioactivity assays were then correlated with platelet adhesion and the extent of platelet release to assess the efficacy of this heparin‐immobilized copolymer as a blood‐compatible material or coating.
The influence of hydrogel functional groups on cell behavior
Authors: Smetana K. , Vacík J. , Součková D. , Krčová Z. , Šulc J. 
Published: December 2004

AbstractThis study provides information on the behavior of macrophages on the surface of the subcutaneously implanted hydrogel strips. Hydrogel containing OH,CONH, and (CH3)2Ngroups induced a spreading of macrophages on the implants. The materials containing SO3H groups slightly, and materials containingCOOH groups more intensively, inhibited spreading of the macrophages. The fusion of macrophages into multinucleate cells was inhibited on the surface of materials containing acidic groups (SO3H, COOH) and increased on the hydrogels containing 30 mol% of alkaline (CH3)2N groups in comparison with hydrogels containing OH or CONH groups. The differences of the behavior of macrophages on the surface of individual types of hydrogels are probably independent on the adsorption of plasma fibrnectin onto the hydrogels. The correlation between the macrophages spreading and fusion and surface charge of the hydrogel implant can be hypothetically explained by electrostatic interaction between macrophages cell membrane and implant.
Surface reactions of calcium phosphate ceramics to various solutions
Authors: Hyakuna Katsufumi , Yamamuro Takao , Kotoura Yoshihiko , Oka Masanori , Nakamura Takashi , Kitsugi Toshiaki , Kokubo Tadashi , Kushitani Hideki 
Published: December 2004

AbstractThe surface reactions of calcium phosphate ceramics have been thought to play an important role in bonding with living bone. Hydroxyapatite (HA), tricalcium phosphate (TCP), and two kinds of apatite‐containing glass ceramics were immersed in three types of solutions with different chemical constituents. The first solution was a physiological saline, the second contained phosphate (PO4), and the third was a balanced salt solution consisting of calcium (Ca), magnesium (Mg), and PO4. After serial incubation periods, changes in the solutions were assessed by measurement of total Ca, Mg, and PO4. The ceramic surfaces were studied using scanning electron spectroscopy, infrared reflection spectroscopy, and thin‐film x‐ray diffraction. The surface reactions of the ceramics were greatly affected by the chemical compositions of the surrounding media. In the complete solution with both Ca and PO4, a carbonated apatite layer was formed on the surfaces of HA, TCP, and the glass ceramics. In comparison to HA and TCP, the glass ceramics were characterized as Ca‐releasing materials, the dissolved Ca creating an apatite layer on the surfaces in a few days, in conjunction with PO4stock in the surrounding media. The immersion test with various solutions proved to be a simple and effective method of assessing surface conditions of ceramic materials.
Biocompatibility of a polyether urethane, polypropylene oxide, and a polyether polyester copolymer. A qualitative and quantitative study of three alloplastic tympanic membrane materials in the rat middle ear
Authors: Bakker D. , van Blitterswijk C. A. , Hesseling S. C. , Koerten H. K. , Kuijpers W. , Grote J. J. 
Published: December 2004

AbstractThe biocompatibility of porous implants made of Estane 5714 F1 polyether urethane, polypropylene oxide, and a poly(ethylene oxide hydantoin) and poly(tetramethylene terephthalate) segmented polyether polyester copolymer (HPOE/PBT copolymer), which were selected as candidates for an alloplastic tympanic membrane, was assessed after implantation in rat middle ears for periods of up to 1 year. Implantation of the materials led to tissue reactions initially associated with the wound‐healing process, whereas after 1 month not only the presence of macrophages and foreign‐body giant cells surrounding the implant materials but also implant degradation were characteristic for a foreign‐body reaction. Macrophages and foreign‐body giant cells dominated the picture of the tissue surrounding polypropylene oxide. The altered morphology of these cells, the persistent infiltration of the implantation sites by exudate cells, and the premature death of five rats in the 1‐year group suggest that polypropylene oxide degradation was accompanied by the release of toxic substances. Estane and copolymer degradation did not induce tissue responses reflecting implant toxicity, and tympanic membranes given these alloplasts showed a normal healing pattern. Inclusions in the cytoplasm of macrophages associated with degradation and phagocytosis of all of the polymers under study were found to contain iron, silicon, titanium, and aluminum. Growth of fibrous tissue and bone, the latter into Estane and HPOE/PBT copolymer implants, indicated appropriate implant fixation by tissue, although macrophages and foreign‐body giant cells were present as well. Especially the fixation of copolymer by ingrowth of bone seems promising in terms of the amount of bone in the pores and the electron‐dense bone/copolymer interface. The latter is indicative for bonding osteogenesis. The HPOE/PBT copolymer is a better candidate for alloplastic tympanic membrane than Estane, and the use of polypropylene oxide cannot be recommended.
Student research award in the graduate degree candidate category, 16th annual meeting of the society for biomaterials, Charleston, SC, May 20–23, 1990. Investigation of a hydroxyapatite and calcium sulfate composite supplemented with an osteoinductive factor
Authors: Damien C. J. , Parsons J. R. , Benedict J. J. , Weisman D. S. 
Published: December 2004

AbstractIn the search for a suitable bone graft substitute, a study was conducted using a material that combined a proven osteconductive composite, hydroxyapatite‐calcium sulfate (HA/CS), with an osteoinductive factor, bovine osteogenic factor (OF). The initial study demonstrated the osteoinductive potential of OF in the rabbit muscle model. Once satisfied that the OF was active, it was added to the HA/CS composite and placed in 8‐mm trephine defects in the rabbit cranium. This HA/CS/OF was directly compared to HA/CS augmented with a control protein, rabbit serum albumin (RSA). Animals were sacrificed at 4 and 8 weeks. Results demonstrated increased bone formation with the addition of the OF to the composite with bridging of the defects, in most cases, by 4 weeks. No bridging was seen, at this time period, in the other defects left unfilled or filled with HA/CS/RSA. Osteogenic factor, with the appropriate delivery system, can induce bone formation in the rabbit muscle. It may also increase the rate of bone formation at early time periods in a bony defect site when the delivery system is the osteconductive composite HA/CS.
Tissue reaction to subcutaneous implantation of a collagen sponge. A histological, ultrastructural, and immunological study
Authors: Anselme K. , Bacques C. , Charriere G. , Hartmann D. J. , Herbage D. , Garrone R. 
Published: December 2004

AbstractThe biocompatibility of a subcutaneously implanted bovine collagen sponge (Haemostagen) was studied in rats by analyzing tissue reactions up to 3 months by histological and ultrastructural methods; in addition, the level of serum antibodies to bovine type I collagen (the major implant collagen) was measured by solid‐phase radio‐immunoassay. By 8 h after implantation, the implant was completely filled with polymorphonuclear cells (PMNs). After 8 days, fibroblasts had developed a granulation tissue within the sponge and the PMNs had almost disappeared. The small residue that remained after 1 month consisted of some densely packed collagen fibrils containing giant cells, which had disappeared by 3 months. No antibodies to bovine type I collagen were found in the sera of implanted rats.
Micromechanical spectroscopy of cartilage proteoglycans: Hydration
Authors: Lamure Alain , Harmand Marie‐Françoise , Lacabanne Colette 
Published: December 2004

AbstractProteoglycan subunits extracted from calf cartilage have been studied with a high resolving power mechanical spectroscopy: the Thermostimulated Creep (TSC). The influence of hydration on TSC spectra shows the existence of two types of bound water: the weakly bound water increases the inertia of proteoglycan and stiffens their structure; the strongly bound water is responsible to a compensation law indicating the existence of a resonance phenomenon at the physiological temperature. Because of the looseness of bonds in weakly bound water, an increase of the local pressure may induce, in vivo, a release of water in tissues. This hypothesis explains perfectly the role of a water pump of proteoglycans in cartilage.
Development and testing of a human collagen graft material
Authors: Quteish D. , Singh G. , Dolby A. E. 
Published: December 2004

AbstractHuman Type I collagen was extracted from placenta using pepsin and salt fractionation. The collagen was characterized by SDS‐PAG electrophoresis dispersed in acidic medium, freeze‐dried, and crosslinked in a 0.25% glutaraldehyde solution pH 4.5 for 2 days. After washing for 7 days and freeze drying the resultant collagen sponge was tested with regard to mechanical, physical, enzymatic degradation properties and biological responses. The modulus of elasticity was found to be 289 ± 10 g/mm2 and the sponge was in soluble in water, buffered saline, or tissue culture medium over a period of 6 weeks with swelling occurring at less than 5% of volume. The sponge had a high fluid binding capacity, amounting to 56 ± 5 mL tissue culture medium per gram of dry weight. Bacterial collagenase produced slow degradation of the sponge with colmplete disappearance by 24 h only when concentrations (200 units enzyme per mg of the collagen sponge) were used. Cytotoxicity studies using human gingival and periodontal ligament fibroblasts revealed less than 5% apparent cytotoxicity or proliferation. Subcutaneous implantation was folllowed by resorption and vascularization over a period of 6–8 weeks. It was concluded that the collagen sponge prepared from human Type I collagen has potential as a graft material in oral surgical procedures.
Small‐caliber polyurethane and polytetrafluoroethylene grafts: A comparative study in a canine aortoiliac model
Authors: Brothers Thomas E. , Stanley James C. , Burkel William E. , Graham Linda M. 
Published: December 2004

AbstractIn vivo stability of a new small‐caliber polyurethane graft (n8) was assessed in a canine aortoiliac model and compared to that of a conventional expended polytetrafluoroethylene (ePTFE) graft (n8). Six months following implantation, marked aneurysmal dilatation to 230 ± 80% (x ± SD) of the original diameter occurred in polyurethane grafts, while dilatation to 110 ± 8% of the original diameter occurred in ePTFE grafts (p < 0.005). Interval patency was 75% for each graft type. Luminal thrombus affected 59% of polyurethane graft surfaces compared to 22% of ePTFE graft surfaces (p < 0.01). Qualitative examination of representative sections of polyurethane conduits demonstrated thick inner capsules with numerous small islands of graft material surrounded by macrophages and bands of mature fibrous tissue, in contrast to the thinner neointima and limited anastomotic pannus ingrowth observed in ePTFE grafts.
Porcine aortic valve bioprostheses: A morphologic comparison of the effects of fixation pressure
Authors: Hilbert Stephen L. , Barrick Mary K. , Ferrans Victor J. 
Published: December 2004

AbstractIt has been suggested that the mechanical durability of glutaraldehyde‐treated porcine aortic valve (PAV) bioprostheses (BPs) may be increased if collagen crimp approximating that observed in native valvular tissue is maintained during preimplantation processing. Among the factors affecting PAV fixation, the magnitude of the pressure applied to the aortic valve during fixation influences the extent of collagen crimp. Polarized light microscopy is useful for both the qualitative assessment of collagen morphology and the quantitative measurement of collagen crimp in BPs. The purpose of this study was to determine the feasibility of using this optical method to detect quantitative differences in PAV collagen crimp following zero‐, low‐, and high‐pressure fixation. The results of this study demonstrate the following: (1) coupling polarized light microscopy and morphometric measurements provides a quantitative method for the evalution of the relationship between fixation pressure and collagen crimp in PAVs; (2) a significant association between increasing fixation pressure and absence of collagen crimp was observed in cords and the midcusp region; (3) collagen crimp length in the cords is affected by fixation pressure; (4) the alteration of collagen crimp by low‐ and high‐pressure fixation does not uniformly affect all regions of the cusp; and, (5) collagen crimp was consistently present in all cusp regions in zero‐pressure fixed PAVs.
The behavior of alloplastic tympanic membranes in Staphlococcus aureus‐induced middle ear infection. II. Morphological study of epithelial reactions
Authors: Bakker D. , van Blitterswijk C. A. , Hesseling S. C. , Daems W. Th. , Grote J. J. 
Published: December 2004

AbstractEpithelial reactions to Silastic, Estane polyether urethane, polypropylene oxide, and a poly(ethylene oxide hydantoin) and poly(tetramethylene terephthalate) segmented polyether polyester copolymer were investigated after implantation in tympanic membranes and submucosa of noninfected and Staphylococcus aureus‐infected rat middle ears. Porous implants made of Estane and polypropylene oxide were completely covered by tympanic‐membrane connective tissue, epidermis, and epithelium in 2 weeks and those made of copolymer in between 2 and 4 weeks postoperatively. Silastic implants, which were dense, were not enveloped by tympanic‐membrane tissue but rejected. Starting in the 6th postoperative month the proliferative activity and structure of both the tympanic membrane epithelium and epidermis became normal except for the presence of iron‐containing secretory epithelium near polypropylene oxide. After initial swelling caused by the surgical trauma, neither the proliferative activity nor the composition of the epithelium covering submucosal implants was affected by the presence of any of the biomaterials. Infection of middle ears bearing implants induced epithelial reactions similar to those associated with infected middle ears without an implant.
Histological and ultrastructural appearance of the hydroxyapatite–bone interface
Authors: De Lange G. L. , De Putter C. , De Wijs F. L. J. A. 
Published: December 2004

AbstractThis article describes the histological and ultrastructural appearance of the interface created in the implantation bed, between bone tissue and implants made of dense sintered hydroxyapatite (HA). Biopsies from dog subjects included: (a) loaded permucosal dental implants for tooth substitution, (b) subperiosteally placed implants for alveolar bone correction, (c) endosseously placed dental root implants to retain ridge form following extraction. The light and electron microscopical results show extensive bone apposition on the osseous sides of the implant surfaces. There is an intimate, direct bone contact without any visible interruption. The bone is of normal lamellar type and continuously connected with the trabecular bone. Bone has grown into the finest surface irregularities of the implant. Collagen fibers of the calcified bone matrix are observed within a distance less than 500 Å from the implant surface. The thin (20–100 Å) electron dense layer at the bone‐implant interface resembled the lamina limitans of organic bone matrix, also seen at the inner walls of the osteocytes lacunes. Deposition of bone gives rise to a biologically stable bone‐implant interface, without disturbance of the physiological bone turnover. This is seen as very favorable for desired long term fixation of implant to bone.
Ectopic induction of cartilage and bone by water‐soluble proteins from bovine bone using a polyanhydride delivery vehicle
Authors: Lucas Paul A. , Laurencin Cato , Syftestad Glenn T. , Domb Abraham , Goldberg Victor M. , Caplan Arnold I. , Langer Robert 
Published: December 2004

AbstractControlled release delivery vehicles for water‐soluble osteogenic proteins from demineralized bovine bone matrix were constructed using polyanhydride polymers. The water‐soluble proteins were isolated from a 4 M guanidine hydrochloride extract of bone matrix. The water‐soluble proteins possessed Chondrogenic Stimulating Activity (CSA) when tested in stage 24 chick limb bud cell cultures, but were incapable of inducing cartilage or bone in vivo when implanted intramuscularly into mice by themselves. The polyanhydride polymers alone were also incapable of inducting ectopic cartilage or bone. However, when the water‐soluble proteins were incorporated into the polymeric delivery vehicle, the combination was capable of inducing cartilage and bone up to 50% of the time. These results demonstrate that it is possible to use polyanhydride polymers as controlled‐release delivery vehicles for soluble bioactive factors that interact with a local cell population.
Release and detection of dental corrosion products in vivo: Development of an experimental model in rabbits
Authors: Reuling Norbert , Wisser W. , Jung A. , Denschlag H. O. 
Published: December 2004

AbstractAn experimental animal model was developed to investigate the release of metal ions from nonprecious dental alloys. Cast specimens of five NiCr‐alloys and CoCr‐alloys were implanted intramuscularly in rabbits for periods of 2, 4, 8, and 12 weeks. The concentrations of nickel, chromium, cobalt, and molybdenum in the implantloaded muscles were determined by electrothermal atomic absorption spectrometry (AAS) and neutron activation analysis (NAA). Reference muscle samples of each animal were analyzed to determine the individual control values. Significant increases in the tissue concentrations of these metals occurred in the immediate vicinity of the implants. Concentration gradients of the corrosion products were found between the implant contact tissue and the implant periphery (p < 0.001). Tissue concentrations of nickel and chromium correlated (r < 0.7). Microprobe analysis before and after implantation of the alloy specimens indicated an even corrosive loss of the alloy surfaces and changes in the surface element distributions. Advantages and limitations of this animal model are discussed, as well as its application in future studies.