Abstract
Hyaluronic acid is a polymer that widely distributed in human coneectissues including the ocular tissues such as tears, cornea, aqueous humor and vitreous body. In ophthalmology, hyaluronic acid has been used as an main ingredient of artificial tear and visco-elastic agent during the intraocular surgeries to tent the anterior chamber in order to protect the corneal endothelium from the mechanical trauma during the operation. Htyaluronic havs been demonstrated to be able to promote the cell viability, cell migration, proliferation of corneal epithelial cells and the wound healing by several mechanism including CD 44 receptor binding, laminin/fibronectin secretion and water retentions, etc. In this project, we intend to modification the material of therapeutic soft contact lens ( hydrowyethyl methycrylate, HEMA) with hyaluronic acid by using simultaneous interpenetrating network to promote the effect of wound-healing of therapeutic contact lens. Low molecular weight HA(MW=50kD,810kD) improves cell migration of human corneal epithelial (HCEpi) cell but cannot promote its adhesion and proliferation. High molecular weight HA(MW=5000kD, 1500kD) repel cell adhesion. This ability can be applied to HA eye drop and anti-adhesion membrane. Because high MW HA can decrease the friction between cornea and eyelid, and the damage of human cornea epithelial cell. HA has several approaches to help cell migration, one of them is to increase the amount of CD44 receptor, regardless of the molecular weight. The increase in the amount of CD44 can explain how HA stimulates HCEpi cell migration. Though the result of HCEpi cell cycle with HA, we note that the S phase cell percentage of the low MW HA is higher than both the high MW HA and the control. But the resulted number of cell proliferation from the experiments is the same as the control. Further research is needed to demonstrate that HA can really improve cell proliferation. The contact lens hydrogels containing HA, the surrounding of polymerized system must be maintained at pH 7.0 to increase the HA solubility and the transparency of hydrogels. The hydrogels were obtained as the water content below 50 % under photo free radical polymerization. If the water content was above 50 % in the polymerization, the hydrogels were not obtained. In SEM images, the HA was clearly observed on the surface of the hydrogels. The hydrogel containing HA has better tensile strength than that without containing HA. But the water content of hydrogel was decreased by increasing HA. The hydrogels that contained HA above 3 wt % exhibited well cell adhesion ability. Through the current study, this novel therapeutic soft contact lens modified with hyaluronan or chitosan has great potential for its applications to corneal epithelial wound healing.