Preparation And Biocompatibility Of Corneal Repair Materials For Corneal Regenration

Corneal disease is the second leading cause of blindness worldwide. Corneal transplantation is the only available treatment currently. However, human donor corneas are extremely tight. The severe shortage of safe, good quality corneal tissues have led to various efforts to develop corneal substitutes. Corneal repair and regeneration brings hope to patients left blind by corneal diseases. Preparing an ideal material for corneal regeneration is the issue to this field. As an ideal corneal regeneration material, it should be transparent, degradable, biocompatible and possess excellent permeability and suitable mechanical property. In this thesis, A15-collagen composite membranes, modified chitosan-collagen crosslinked membrane and modified chitosan-gelatin crosslinked membrane were perpared by crosslinking to gain materials for corneal repair, which were transparent, biocompatible and held suitable mechanical property and permeability. Their intraocular biocompatibility and ability to promote generation of new keratocytes were researched preliminarily.A15-collagen composite membranes and collagen crosslinked membrane were fabricated by crosslinking with EDC and NHS. Equilibrium water content, optical properties, permeability and mechanical properties were tested. It was found that with the increase of A15content, their equilibrium water content and transparency increased, refractive indices and wet tensile strength decreased. The wet tensile strength of the composite membranes with A15content above10%was about0.1MPa. The composite membranes exhibited good glucose, tryptophan and NaCl permeability, and the composite membrane with2%A15content showed the best permeability. The composite and collagen membrane were basically nontoxic, human corneal epithelial cells (HCEC) attached, grew and proliferated well on them. The composite membranes implanted in rabbits maintained high optical clarity after transplantation. No inflammatory and rejection reaction was observed. New stromal keratocytes regeneration was observed on the surface of the implants5months postoperatively, indicating good intraocular biocompatibility of the composite membranes.To improve the intraocular biocompatibility of collagen membrane, a modified chitosan with excellent antiinflammatory and antimicrobial activity was incorporated into collagen to produce modified chitosan-collagen crosslinked membrane. The properties and performances of the composite membrane were compared with collagen crosslinked membrane. The results showed that the incorporation of modified chitosan enhanced the transparency of collagen membrane, but refractive indices and equilibrium water content decreased. The addition of modified chitosan to collagen significantly enhanced the wet tensile strength of the composite membrane, which reached2MPa. The permeability of the composite and collagen membranes to glucose, tryptophan and NaCl were superior or comparable to that of human corneas. HCEC attached, grew and proliferated well on the composite membrane. The intraocular transparency of the composite membrane decreased when implanted in rabbits. No inflammatory and rejection reaction was observed after transplantation. The composite membrane preliminarily showed the ability to induce stromal keratocytes regeneration, indicating good intraocular biocompatibility.Modified chitosan-gelatin crosslinked membrane were fabricated by crosslinking with EDC and NHS. The properties and performances of the modified membrane were compared with chitosan-gelatin crosslinked membrane. The results indicated that the modified membrane had higher equilibrium water content, refractive indices and lower wet tensile strength than chitosan-gelatin membrane. Both membranes possessed high transparency. The modified membrane showed good permeability to glucose, tryptophan and NaCl. HCEC grew and proliferated well on both membranes. The composite membrane implanted in rabbits maintained high optical clarity after transplantation. No inflammatory and rejection reaction was observed. The implant degraded completely16weeks post-operation without inducing inflammatory reaction, indicating good intraocular biocompatibility. On the contrary, chitosan-gelatin membrane caused severe inflammatory reaction when implanted in rabbits, indicating poor intraocular biocompatiblity.