We are studying two material factors that may affect angiogenesis. The first, porosity, is based upon previous in vivo work that demonstrated a correlation between porosity and the number of vascular structures located close to the material. The second is coating the material with molecules, such as extracellular or matrix proteins. For example, we are currently immobilizing a peptide from SPARC that has shown angiogenic activity in vivo. To facilitate these studies, we are developing in vitro assays to study angiogenesis in the context of a biomaterial. For example, we have developed an assay to measure migration, a crucial step in angiogenesis. A teflon fence is used to grow endothelial cells to confluence in a well-defined area on the material. Once the fence is removed, the migration on various surfaces can be measured. ESCA is used to characterize the composition and chemistry of the surfaces.