Study On Modification Of PVA Optical Center Material For Artificial Cornea

Artificial cornea is an artificial refractive device which used as a substitute for lesion cornea to cure corneal disease, the artificial cornea is similar to donor cornea and made from biomedical material. Donor cornea can not meet the needs of corneal disease treatment because of the large shortage and the low success rate of allogeneic keratoplasty. So it has great significance to develop artificial cornea. After the transplant surgery, there are some problems such as abnormal position or prolapse of artificial cornea and proliferative membrane formed upon or under the optical center. Optical center material is the core of artificial cornea, its performance has a great impact on the prospect of artificial cornea.Polyvinyl alcohol(PVA) hydrogels have good hydrophilic, mechanical properties, optical properties and biocompatibility. The result of previous study showed when the artificial cornea made from PVA hydrogels were transplanted into animal eyes, the properties of PVA hydrogels can meet the basic needs of artificial cornea, but there were some corneal epithelial cells adhesion or grown on the optical center in the later period. In this paper, PVA hydrogel has been made into the optical center and has been modified to obtain an artificial cornea optical center material which have not only excellent basis performance, but also the property of resist epithelial cells adhesion on optical center.In this paper, artificial cornea optical center material(PVA hydrogels) has been modified by methods such as coating, composite and surface grafting, properties of modified PVA hydrogel were investigated. The main content and results are described as follows:Firstly, N, N-dimethylacrylamide(DMA) and Methacrylic acid(MAA) wer e used as comonomers to prepare the copolymer N,N-dimethylacrylamide-co-Methacrylic acid(DMA-MAA), copolymer DMA-MAA were characterized by FTIR and modified on the surface of PVA hydrogel by coating. The impact of concentration of DMA-MAA on transmittance, moisture content, swelling, hydrophilic and resist cells adhesion property of PVA hydrogel were investigated. The result showed that the PVA hydrogel modified by DMA-MAA possessed high visible light transmittance(above 90%), moisture content is 71%~73%, equilibrium swelling ratio is 3.5~3.7, the time of swelling equilibrium is 45 min, the water contact angle of modified PVA hydrogel decresed from 41° to 14°. The modified material showed excellent cell adhesion resistance.Secondly, heparin sodium/polyvinyl alcohol(HS/PVA) composite hydrogel was prepared by cyclic freezing-thawing. Effect of mass fraction of heparin sodium on visible light transmittance, moisture content, equilibrium swelling, hydrophilic, mechanical property and percentage of heparin sodium release of composite hydrogel were studied. Results show that the introduction of heparin sodium into the structure of PVA can enhance the moisture content, hydrophilic and equilibrium swelling of HS/PVA composite hydrogel, simultaneously, can reduce visible light transmittance and mechanical properties. Visible light transmittance is above 92%, moisture content is 72%~78%, equilibrium swelling ratio is 4.0~4.5, time of swelling equilibrium shortened from 60 min to 45 min, water contact angle decresed from 41° to 22°, the tensile strength of composite hydrogel is 0.55~0.76 MPa and elongation at break is more than 200%. The release of heparin sodium from HS/PVA composite hydrogel can resist cell adhesion.Thirdly, heparin(Hep) grafted to PVA hydrogel surface by covalent grafting, the modifiers on the surface of hydrogel were characterized by ATR-FTIR. The impact of concentration of 3-aminopropytriethoxysilane(APTS) and Hep on transmittance, moisture content, swelling, hydrophilic and the amount of immobilized heparin on the PVA hydrogel surface were investigated. The result show that the visible light transmittance of modified PVA hydrogel was above 94%, moisture content is 68%~72%, time of swelling equilibrium is about 60 min and equilibrium swelling ratio is 3.0~3.5, hydrophilic obtain significantly improved and the water contact angle decresed from 41° to 28°. The surface of PVA hydrogel could covalently binding with some of heparin molecules, the heparin molecule possessed excellent hydrophilic and high negative charge which can enhance the property of resist cells adhesion of PVA hydrogel.Finally, the biocompatibility of modified PVA hydrogel material was evaluated by acute systemic toxicity test, invitro cytotoxicity test and intradermal reaction test. The results showed that, extract liquid of samples did not lead to animal death or signs of systemic toxicity, the invitro cytotoxicity grade were 0 or 1, the intradermal reaction were extremely slight. The experiments proved that the biocompatibility of modified PVA hydrogel which used as medical material has achieved the national standard.