Characterization of Chemically and Topographically Modified Siloxane Elastomer for Controlled Cell Growth
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Characterization of Chemically and Topographically Modified Siloxane Elastomer for Controlled Cell Growth Amy L. Gibson, Leslie H. Wilson, Wade R. Wilkerson, Adam W. Feinberg, Charles A. Seegert, Ronald H. Baney, and Anthony B. Brennan Department of Materials Science and Engineering, Biomedical Engineering Program University of Florida, Gainesville, Fl 32611, USA ABSTRACT A main limitation of biomedical devices is the inability to start, stop, and control cell growth making it crucial to develop biomaterial surfaces that induce a desired cellular response. Micropatterns of ridges and pillars were created in a siloxane elastomer (Dow Corning) by casting against epoxy replicates of a micromachined silicon wafer. Silicone oils were incorporated to determine the change in modulus and surface energy caused by these additives. SEM and white light interference profilometry verified that the micropatterning process produced high fidelity, low defect micropatterns. Mechanical analysis indicated that varying the viscosity, weight percent and functionality of the added silicone oil could change the elastic modulus by over an order of magnitude (0.1-2.3 MPa). As a self-wetting resin, silicone oils migrate to the surface, hence changing the surface properties from the bulk. Both topographical and chemical features define the surface energy, which in combination with elastic modulus, dictate biological activity. The results imply that the morphology, mechanical properties and surface energy of the siloxane elastomer can be modified to elicit a specific cell response as a function of engineered topographical and chemical functionalization. INTRODUCTION The ability to predict and control a biological response to a biomedical device is of great significance to the success of the biomaterial. Knowledge of the cell’s adhesion on a surface is crucial for technological improvements with medical tissue grafts and for anti-fouling marine coatings [1,2]. By determining the aspects of the material and the surface that influence contact guidance and bioadhesion, there is an opportunity to design a system to elicit a desired response at biointerfaces. We theorize that biological activity will be dictated by mechanical properties, in particular elastic modulus, and surface energetics, which are defined by topographical and chemical features. An in depth characterization of the bulk and surface properties of silicone elastomers has been examined here. Siloxane elastomers, as a biological substrate with a broad application range, have been engineered both topographically and chemically with reliability. The 5 µm to 20 µm topography features, which have been shown to influence cell function, have been reproduced here with high fidelity [3-5]. In order to examine the effects of elastic modulus and surface energy, the silicone elastomer was modified with linear and branched, nonfunctional and vinyl functionalized silicone oils. In order to understand the biological response to the surface, porcine vascular endothelial cells (PVECs) were cultured on
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