CORNEAL TRANSPLANT(using hydrogel)

Abstract.

To solve the shortage of the donor cornea in Japan, scientists are developing a poly(vinyl alcohol) hydrogel based keratoprosthesis. Minimum requirements for a keratoprosthesis include light transparency, non-toxicity, and nutrition and fluid permeability. Earlier clinical trials had frequently failed because corneal epithelial down growth occurred between the host cornea and the materials, and the materials were finally rejected from the host cornea. The major cause of this rejection is the weak adhesion between the host cornea and the prosthesis. In order to achieve the firm fixation of the artificial cornea to host cornea, composites of collagen-immobilized poly(vinyl alcohol) hydrogel with hydroxyapatite(PVA-HAp nano composites) were synthesized. The preparation method, characterization, and the results of corneal cell adhesion and proliferation on the composite materials were studied. The PVA-HAp nano composites were successfully synthesized. Chick embryonic keratocyto-like cells were well attached and proliferated on the PVA-Hap composites. This material showed potential for keratoprosthesis.

Introduction
A wide variety of corneal disorders caused by corneal disease and some accidents such as corneal ulcer, chemical burn, etc. are treated by transplantation such as penetrating keratoplasty, lamellar keratoplasty, and deep lamellar keratoplasty, and the success rate is high compared to other tissue transplants. However, many countries suffer from a shortage of donor corneas, and the development of an artificial cornea may be a solution towards solving this problem. In the past 50 years, several groups have attempted to develop reliable artificial cornea, but the trials have frequently failed because of poor biocompatibility. In general, clinically available synthetic devices do not support an intact epithelium, which poses a risk of microbial infection or protrusion of the prosthesis. To solve the problem, we have been developing a poly(vinyl alcohol)(PVA) hydrogel based keratoprosthesis [2-5]. Previously we have found that the immobilization of Type I collagen on the poly(vinyl alcohol)(PVA) hydrogel disc was effective in supporting adhesion and growth of the corneal epithelium and stromal cell in vitro. However, the adhesion was not strong enough to prevent the down growth of the corneal epithelium. Hydroxyapatite(HAp) is well known as one of the best biocompatible materials and it has been applied for percutaneous devices. The result was very promising and the device can prevent epithelial down growth[6-7]. In this study, we synthesized various PVA-hydroxyapatite(PVA-HAp) nanocomposites and modified them by Type I collagen (PVA-COL- HAp) to achieve firm adhesion between the host corneal tissue and the keratoprosthesis. Hydrogel disc of PVA-COL and PVA-COL-HAp and nanofiber sheet of PVA-COL and PVA-COL-HAp were prepared to compare the efficacy of the materials and the influence of the morphology. The preparation method, characterization, and the results of the corneal cell adhesion and proliferation on the composite materials were studied.

By CH . ANKITA 11307010 BME 3rd Year