Artificial Cornea Design for Corneal Tissue Infiltration Into Porous PDMS Scaffold

Abstract

Abstract: : Purpose:Synthetic corneal devices are being investigated for cases where a transplant is ineligible. An important measure of success is the integration of the device with native host tissue to prevent complications such as tissue melting at the device tissue interface and extrusion of the device from the eye. It is believed that a combination of a porous scaffold and delivery of appropriate growth factors and cytokines will increase the wound healing response of corneal stromal fibroblasts allowing them to grow into the device. Herein we report on an alginate based microparticle growth factor delivery system that can be incorporated into a porous poly (dimethylsiloxane) (PDMS) scaffold. Methods:Alginate microparticles containing albumin as a model protein and fibroblast growth factor for stimulating corneal stromal cells were fabricated using external gelation. Release of the proteins under physiologic conditions was measured. The microspheres were also incorporated into a porous PDMS foam and the resultant distribution characterized microscropically. Biological activity of the released proteins will be assessed by receptor binding assays and by measuring the response of human corneal stromal cells to the released proteins. Results:The alginate microspheres were found to have minimal defects and a small size distribution when examined using light microscopy at 500±50 microns. The microspheres can be dried by freeze drying and rehydrated to their initial size in sodium chloride. The microspheres were successfully incorporated into a PDMS foam. Microencapsulation and subsequent release of bovine serum albumin from the microcapsules into phosphate buffered saline and sodium chloride was found to occur over a period 4 hours or 2 weeks. Incorporation of the microcapsules into a polymer matrix will enhance the release by presumably delaying the release. Western blotting will be used to examine the degradation of the released protein. Future release studies will involve bFGF and will be coupled with receptor assays to check for retained activity. Conclusions:The external gelation method to produce microspheres has been optimized to minimize size distribution and defect occurrence. Encapsulation and release of BSA has been established. Microspheres have been successfully incorporated into porous PDMS. An efficient re–swelling procedure has been established, allowing for the manipulation of microsphere diameter to occur.

Keywords: keratoprostheses • growth factors/growth factor receptors • cornea: stroma and keratocytes