Development of hydrogel-based keratoprostheses: a materials perspective

Abstract

Research and development of artificial corneas (keratoprostheses) in recent years have evolved from the use of rigid hydrophobic materials such as plastics and rubbers to hydrophilic, water-swollen hydrogels engineered to support not only peripheral tissue integration but also glucose diffusion and surface epithelialization. The advent of the AlphaCor core-and-skirt hydrogel keratoprosthesis has paved the way for a host of new approaches based on hydrogels and other soft materials that encompass a variety of materials preparation strategies, from synthetic homopolymers and copolymers to collagen-based bio-copolymers and, finally, interpenetrating polymer networks. Each approach represents a unique strategy toward the same goal: to develop a new hydrogel that mimics the important properties of natural donor corneas. We provide a critical review of these approaches from a materials perspective and discuss recent experimental results. While formidable technical hurdles still need to be overcome, the rapid progress that has been made by investigators with these approaches is indicative that a synthetic donor cornea capable of surface epithelialization is now closer to becoming a clinical reality.

Figure 1

The AlphaCor keratoprosthesis. (Image from Hicks et al, Cornea 24(8) 2005 (39).)

Figure 2

(a) Schematic of the photolithographic patterning process by which a PEG/PAA core-and-skirt keratoprosthesis is fabricated. This polymerization step is followed by swelling with the second network precursor, removal of excess monomer, and polymerization of the second network. The result is a porous hydrogel (b) with pores that go all the way through the bulk of the gel (cross-section, c), (d) A single-piece PEG/PAA keratoprosthesis fabricated by photolithographic patterning.