The long-term objective of this project is to develop novel porous silicon-based ophthalmic implants as scaffolds for autologous cell transfer to the eye, for the treatment of human ocular surface disease. The proposed base component for such implants is nanostructured porous silicon in the form of microparticles. Porous silicon is a relatively non-toxic, completely biodegradable material that is easily prepared and modified, can be loaded efficiently with bioactives, shows excellent biocompatibility and supports the growth of mammalian ocular cells. The addition of a resorbable organic polymer component to the structure adds mechanical flexibility, ease of handling, and reduction of any possible deleterious effects based on shape of the porous silicon microparticles. Clinically relevant rat models of ocular surface disease will be used. This proposal addresses two specific aims: (1) to fabricate novel porous silicon/resorbable polymer composites, functionalize their surfaces, and load them with bioactive species, to generate supports for the transfer of expanded populations of rat oral mucosa-derived stem cells to the ocular surface, and to provide an artificial stem cell niche; and (2) to explore the potential of these implants carrying autologous cells to modulate ocular surface disease, following transfer to the eye of the rat in vivo. Research Design and Methods: (1) Composites of porous silicon microparticles and electrospun poly(-caprolactone) or other resorbable polymers will be fabricated, surface-derivatized, characterized, and loaded with bioactives such as soluble growth factors. The properties of these composite will be tuned by the composite structure but also by the properties of the porous silicon microparticles present. Variation of the porosity of the porous silicon component will alter the rate of silicon degradatio and lifetime of the matrix. Altering the surface chemistry will not only affect porous silicon degradation kinetics, but with judicious selection of appropriate biomolecules adsorbed on to the porous silicon will improve the attachment, survival and growth of epithelial cells. (2) Rat oral mucosal epithelial cells will be expanded on the composite materials and the differentiation status of cells examined by staining for phenotype specific markers. Ex vivo expanded populations or explants containing putative adult stem cells and transient amplifying cells will be transplanted to the rat ocular surface, to test their ability to repair a damaged ocular surface. Impression cytology of the central cornea followed by polymerase chain reaction will be used to detect donor cell genomic DNA on the ocular surface, and cell tracker dyes will be used to visualize migration of donor cells. The cell donors and recipient rats will be of the same inbred strain, so that no immunological rejection will occur.