The proposed studies are directed toward obtaining a better understanding of the mechanisms of infection of implanted cardiovascular prostheses. The hypothesis is that material surface interactions with flowing blood lead to alteration of basic pathophysiologic mechanisms, which increase the probability of bacterial interaction and infection. The studies emphasize the use of clinically derived human materials, i.e., blood and bacteria, and clinically relevant cardiovascular materials coupled with controlled in vitro and in vivo systems to systematically and comprehensively elucidate infection mechanisms with prostheses. The overall goals of the project are to: 1] determine and quantify specific mechanisms of bacterial adhesion, 2] determine and quantify shear dependent non-specific mechanisms of bacterial adhesion, 3] evaluate leukocyte (PMN and monocyte) adhesion on materials, as mediated by plasma proteins and complement activation, in the presence of suspended and reseeded S.epidermidis under dynamic flow conditions, 4] investigate bacteria/leukocyte/biomaterial interactions which alter leukocyte function and microbial killing, 5] design, prepare and characterize biomimetic materials with bacteria-resistant properties that will undergo surface-induced assembly on cardiovascular biomaterials, and 6] utilize a biomaterial infection model in rats to identify in vitro to in vivo correlations. The experimental approach utilizes the variable sheer stress rotating disk system and a new laminar flow system to determine interactions important in human blood protein/platelet/leukocyte interactions with S. epidermidis and clinically relevant biomaterials and novel bacteria-resistant biomaterial coatings. Quantification of bacterial interactions will be accomplished using high-resolution fluorescence microscopy, confocal and atomic force microscopies. Shear-dependent specific and non-specific mechanisms of bacterial adhesion will be identified. Leukocyte and monocyte adhesion and activation on biomaterials in the presence of S. epidermidis under variable flow will be characterized and correlated with leukocyte receptor expression, cell activation markers and cell function assays. Novel biomaterial design will be based on oligosaccharide surfactant polymer coatings containing a polymeric backbone with two types of side chains: one to facilitate adsorption to biomaterial surfaces, the other to generate a bacterial resistant surface. The applicant will optimize both the adsorption characteristics of the coating and its bacterial resistance through modification of the side chains. The biomaterial infection model in rats will be used to test the validity of the in vitro models, as well as the efficacy of the biomimetic coatings
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