The Development of Surface Roughness and Implications for Cellular Attachment in Biomedical Applications
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The Development of Surface Roughness and Implications for Cellular Attachment in Biomedical Applications Bruce Banks1, Sharon Miller1, Kim de Groh1, Amy Chan2 and Mandeep Sahota3 1 NASA Glenn Research Center, Cleveland, Ohio 44135, U.S.A. 2 Ohio Aerospace Institute, Cedar Point Road, Cleveland, Ohio 44142, U.S.A. 3 Cleveland State University, Cleveland, Ohio 44115-2406, U.S.A. ABSTRACT The application of a microscopic surface texture produced by ion beam sputter texturing to the surfaces of polymer implants has been shown to result in significant increases in cellular attachment compared to smooth surface implants in animal studies. A collaborative program between NASA Glenn Research Center and the Cleveland Clinic Foundation has been established to evaluate the potential for improving osteoblast attachment to surfaces that have been microscopically roughened by atomic oxygen texturing. The range of surface textures that is feasible depends upon both the texturing process and the duration of treatment. To determine whether surface texture saturates or continues to increase with treatment duration, an effort was conducted to examine the development of surface textures produced by various physical and chemical erosion processes. Both experimental tests and computational modeling were performed to explore the growth of surface texture with treatment time. Surface texturing by means of abrasive grit blasting of glass, stainless steel and polymethylmethacrylate surfaces was examined to measure the growth in roughness with grit blasting duration by surface profilometry measurements. Laboratory tests and computational modeling was also conducted to examine the development of texture on Aclar (chlorotrifluoroethylene) and Kapton polyimide, respectively. For the atomic oxygen texturing tests of Aclar, atomic force microscopy was used to measure the development of texture with atomic oxygen fluence. The results of all the testing and computational modeling support the premise that development of surface roughness obeys Poisson statistics. The results indicate that surface roughness does not saturate but increases as the square root of the treatment time. INTRODUCTION The degree of cellular attachment to polymer surfaces has been shown to significantly increase by providing a textured surface as opposed to a smooth surface for peritoneal implants in rats [1-2]. Such tests were performed by comparing argon ion beam sputter textured and sputter polished polytetrafluoroethylene (PTFE Teflon) implant surfaces. The surface texturing produced submicron to multimicron sized cones on what would otherwise be rather smooth surfaces. The number of cells attached per 4x104 cm2 was only ~12 for ion sputter polished PTFE, but was 270 for ion beam sputter textured PTFE after 2 days of implantation [12]. The principal cells attached were macrophages, lymphocytes and to a lesser degree mast cells. Atomic oxygen has been shown to produce surface textures in almost all hydrocarbon or halocarbon polymers. The resulting textures are quite simi
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