Designing Novel Biomaterials for Cornea Replacement

Artificial corneas, also known as keratoprostheses (KPros), are an alternative cornea replacement therapy when donor cornea is either inappropriate or inaccessible to a patient. KPro recipients often have preexisting ocular diseases, ocular tissue injury, or a history of corneal graft failure. While a number of KPro models are available on the market, each fails to completely address one or more of the following vital parameters: host integration, mass transport, tissue epithelialization, or innervation. This study presents biomaterials that can potentially improve stable host integration and long term vision restoration. KPros made with poly (2-hydroxyethyl methacrylate) (PHEMA) - poly (methyl methacrylate) (PMMA) (PHEMA-PMMA) and copolymers made with of PHEMA and PEG (polyethylene glycol) are structurally, mechanically, and biologically appropriate for corneal replacement. The center region of the KPro is optically transparent to permit vision; the outer rim of the device is porous to permit tissue ingrowth. Following the addition of cell adhesion components (collagen type I) human corneal fibroblasts proliferated on the porous skirt structures. Mechanical tensile data indicated that the KPro structures are strong enough to resist rupture under the mechanical forces of the eye. PHEMA-PMMA based KPros are mechanically stable enough to be sutured in as full thickness corneal replacement devices. PHEMA and PEG copolymers, mechanically weaker than PHEMA-PMMA, are better suited for suture-less cornea replacement strategies. SEM and Micro CT data show that the pores in the skirts are large enough to permit cell ingrowth. In vivo, healthy tissues penetrate the voids of the porous copolymers. Since diseased ocular tissue is more reluctant to colonize synthetic biomaterials compared to natural-synthetic hybrids, the each skirt’s amenability to cell adhesion component addition is vital to the survival of the KPro in the target patient population. A cell adhesive KPro skirt with a high density of cell permeable pores and physiologically relevant mass transport could potentially facilitate the stable integration of a KPro into ocular tissue.