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  • 1
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: One of the major clinical complications in the biomedical application of synthetic materials is the incidence of implant-associated infections. Such infections are very often induced by Staphylococcus aureus. To obtain information on tissue reactions and minimal bacterial challenge needed to create an infection related to untreated implant surfaces, we injected polyurethane tubing segments with a series of Staphylococcus aureus. The segments were subcutaneously implanted in rats. Implantation periods varied from 2, 5 and 10 days to 3 weeks. Specimen were evaluated using light and transmission electron microscopy. At least 0.25×104 of Staphylococci aureus were needed to clearly recognize that bacteria had been injected in the polyurethane tubing segments. The evidence was indirect, showing high infiltration and activation of neutrophils and macrophages, but not bacteria. Furthermore, 0.25×106 S. aureus were needed to induce a persistent specific inflammatory reaction with high concentrations of lymphocytes, i.e. mainly plasma-cells, at 3 weeks. The results indicate that this model functioned well to obtain the wanted information. Results are discussed with respect to (a-) specific inflammatory reactions occurring with (bacterial-challenged) biomaterials. Ultimately, our goal is to develop infection-resistant materials, for which the in vivo model developed may be used to qualify the processed materials
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 5 (1994), S. 671-678 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Although in the last few years in general the biocompatibility of biomaterials has significantly improved, unwanted tissue reactions are often observed resulting in early resorption of the biomaterial, loosening of the implant or in a chronic (immunologic) response. From immunologic studies it is known that inflammatory reactions can be modulated by use of (anti) growth factors or anti-inflammatory drugs. Before this can be employed the role of individual factors (humoral and cellular) involved in the inflammatory reaction against biomaterials has to be studied. In this part of the study the role of macrophages is studied with and without depletion by use of the liposomes-mediated macrophage suicide technique. Crosslinked dermal sheep collagens were used as biodegradable test materials. The results showed that macrophage depletion increases vascularization, and decreases the infiltration of granulocytes into the collagens. The foreign body reaction, i.e. the infiltration of macrophages and giant cells was significantly inhibited, resulting in a strongly delayed degradation time of the biomaterials. However, macrophage depletion did not inhibit attraction of fibroblasts and even resulted in increased formation of autologous rat-collagen, which improved the biocompatibility and the function of the biomaterials as a tempory scaffold.
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  • 3
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The aim of this study was to evaluate short-term peripheral nerve regeneration across a 10-mm gap, using a biodegradable poly(DL,-lactide-ε-caprolacton) nerve guide, with an internal diameter of 1.5 mm and a wall thickness of 0.30 mm. To do so, we evaluated regenerating nerves using light microscopy, transmission electron microscopy and morphometric analysis after implantation of 12-mm nerve guides in the sciatic nerve of the rat. Evaluation times ranged from 3-10 weeks. Three weeks after reconstruction, myelinated nerve fibers could be observed in the distal nerve stump. Ten weeks after reconstruction, the regenerating nerves already resembled normal nerves. In conclusion, we show that poly(DL,-lactide-ε-caprolacton) nerve guides can be successfully applied in the reconstruction of severed nerves in the rat model. Furthermore, we have observed the fastest nerve regeneration described thus far, after reconstruction using a biodegradable nerve guide. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 4
    ISSN: 0021-9304
    Keywords: T cells ; phagocytosis ; collagens ; biocompatibility ; biomaterials ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Unwanted tissue reactions are often observed resulting in events such as early resorption of the biomaterial, loosening of the implant, or a chronic (immunologic) response. From immunologic studies it is known that inflammatory reactions can be modulated by use of (anti)-growth factors or anti-inflammatory drugs. Before this can be employed with respect to biomaterials, the role of individual factors (humoral and cellular) has to be studied. In this part of the investigation, the role of T cells was studied by use of T-cell-deficient (nude) rats and control (AO) rats. Hexamethylenediisocyanate-crosslinked dermal sheep collagen (HDSC) was selected as the test material. The results showed that T cells or T cell-related factors played a prominent role in the attraction of macrophages and the formation of giant cells, their antigen presentation, and their phagocytotic capacity. As a consequence, degradation of HDSC was strongly delayed. This study also showed that infiltration of fibroblasts and creation of stromal areas in HDSC was restricted to areas subjected to degradation. However, in time, absence of T cells resulted in increased formation and maturation of autologous rat collagen. Results obtained suggest that the inflammatory reaction to biomaterials might be modulated by controlling T-cell activation. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 398-406, 1998.
    Additional Material: 11 Ill.
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  • 5
    ISSN: 0021-9304
    Keywords: biomaterials ; polyurethanes ; infection ; infection resistance ; surface modification ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Tissue reactions to implantable pacemaker leads were investigated in an early infection model in rabbits. Both standard leads and surface-modified leads were used. The surface modification technique was applied to achieve controlled release of the antibiotic gentamicin. The insulating polyurethane tubing material of the leads was provided with an acrylic acid/acrylamide copolymer surface graft and then loaded with gentamicin. Implantation periods varied from day 4, to week 3½, to week 10. We investigated tissue reactions in the absence of an infectious challenge and also the efficacy of surface-modified leads in preventing infection after challenge with Staphylococcus aureus was evaluated. It was demonstrated that the applied surface modification did not induce adverse effects although during early postimplantation an increase in infiltration of granulocytes and macrophages and wound fluid and fibrin deposition were observed. After bacterial challenge, standard leads were heavily infected at each explantation period, denoted by abscesses, cellular debris, and bacterial colonies. In contrast, little or no infection was observed, either macroscopically or by bacterial cultures, with the surface-modified leads. Microscopy showed little evidence of the bacterial challenge, and that primarily at day 4. It was concluded that the applied surface modification demonstrated enhanced infection resistance and thus represents a sound approach to the battle against infectious complications with biomaterials. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 142-153, 1998.
    Additional Material: 12 Ill.
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