| Sufficient oxygen and other nutrients are necessary for maintaining corneal integrity andfunctions. In the case of the avascular cornea, oxygen and nutrients diffuse largely from theatmosphere, tear film and vitreous humour. After cornea repairing materials implantation, theextend and quantities of oxygen and other nutrients diffusing into the cornea mainly dependon the diffusion properties of the materials, so diffusion properties are key characteristics ofcornea repairing materials. In this essay, we designed and installed diffusion measuringdevices, and measured the diffusion properties of a series of cornea repairing materials tooxygen, glucose, tryptophan and sodium chloride, to research the influencing factors of thediffusion properties of the materials.We designed and installed oxygen permeation measuring device with the gaschromatogram as the oxygen volume detector. Oxygen permeation of three materials weremeasured. Comparison of the results of the oxygen permeation measuring device we installedand the Illinois8003device demonstrated that, in the range between10-15to10-12mLO2·cm·cm-2·s-1·Pa-1, our device has applicability and accuracy.Diffusion cells were designed and installed to measure the diffusion properties of thematerials to glucose, tryptophan and sodium chloride. Measuring results showed that thediffusion cells we made were suitable for measurement of the three matters.Chitosan membranes with four different deacetylation degree were prepared, anddiffusion properties of the membranes to oxygen, glucose, tryptophan and sodium chloridewere determined. In the case of dry membranes, the oxygen permeability decreased from4.01×10-15mLO2·cm·cm-2·s-1·Pa-1to3.74×10-15mLO2·cm·cm-2·s-1·Pa-1as the deacetylationdegree increased from77.1%to96.7%, which resulted from the increasing crystalline of themembranes. In the other hand, oxygen permeability of the wet membranes and diffusionproperties to the three matters increased as the deacetylation degree increased. Whendeacetylation degree increased from77.1%to96.7%, oxygen permeability increased from0.73×10-12mLO2·cm·cm-2·s-1·Pa-1to2.01×10-12mLO2·cm·cm-2·s-1·Pa-1，diffusion coefficient ofglucose increased from3.09×10-7cm2·s-1to3.47×10-7cm2·s-1，tryptophan from3.79×10-7cm2·s-1to4.35×10-7cm2·s-1，and sodium chloride from8.33×10-7cm2·s-1to9.12×10-7cm2·s-1. This is mainly because the equilibrium water content of the membranes increased as thedeacetylation degree increased, and water in the materials made diffusion easier.The EDC-crosslinking blend membranes were made with different ratio between chitosanand collagen. Diffusion properties of the blend membranes to oxygen, glucose, tryptophanand sodium chloride were determined. Results showed that permeability of the blendmembranes increased with the increasing ratio of collagen, and decreased with increasingamount of crosslinking agent. As the ratio of collagen increased from0to45%，oxygenpermeability of the wet membranes increased from2.01×10-12mLO2·cm·cm-2·s-1·Pa-1to5.41×10-12mLO2·cm·cm-2·s-1·Pa-1, diffusion coefficient of glucose increased from3.47×10-7cm2·s-1to10.67×10-7cm2·s-1, tryptophan from4.2×10-7cm2·s-1to12.45×10-7cm2·s-1, andsodium chloride from9.12×10-7cm2·s-1to32.14×10-7cm2·s-1.Comparison of the resultsindicated that diffusion properties of the blend membranes were mainly affected by theequilibrium water content. |
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