Study On The Physical-chemistry Properties For The Process Of Drug Release From PVA Hydrogel

Poly(vinyl alcohol)(PVA) hydrogel is non-toxic, non side-effect, with good elasticityand biocompatibility. They have been used extensively as a drug release carrier. In order touse hydrogel as drug carrier for controlled release effectively, we studied thephysical-chemistry properties for the process of drug release from PVA hydrogel. There are4 parts in this work.1. Study on the swelling ratio of PVA hydrogels and its other physical properties. Therelative molecular weight of PVA is calculated by measuring the viscosity of its aqueoussolution. PVA hydrogels were prepared by a physical method of repeat freezing andthawing. The swelling ratio of the hydrogels at several temperatures was determined. Thecontent of water in PVA hydrogel was determined by a TG apparatus. Experimental resultindicates that, the swelling rate and the equilibrium swelling ratio of PVA hydrogelincrease with the rise of temperature.2. Study on the release rate of salicylic acid from PVA hydrogel. A slice form of PVAhydrogel containing salicylic acid was prepared by physical method. The interactionbetween the drug and polymer was studied by FTIR method and the factors influencing thedrug release were investigated. Kinetic models were applied to fit the drug release data, and the release mechanism was analyzed from the model parameters. Experiment resultsindicate that, the hydrogen bonds between hydroxyl of PVA and salicylic acid leads to thecompatibility between them. The drug release rate is accelerated with the rise oftemperature and decreased with the increase of drug loadage. The fitting result suggests afirst-order kinetic equation for salicylic acid release.3. Study on the release rate of silybin from PVA hydrogel. Some physical and chemicalparameters such as purity, melting enthalpy of silybin and the concentration of silybin in water weremeasured, a slice form of PVA hydrogel containing silybin was prepared by physical method.The release rate of silybin from PVA hydrogel was measured, and the factors influencingdrug release were investigated. Kinetic models were applied to fit the drug release data, and the release mechanism was discussed. Experimental results indicate that, the drugrelease rate was accelerated with the increase in temperature. The release rate was large atthe beginning stage, and slowed down at the following release stage. After 10 hours,equilibrium was reached. Kinetic analysis suggests a zero-order kinetic mechanism.4. Study on the release rate of salicylic acid from a PVA/gelatin mixing hydrogel.The mixing hydrogel with different PVA to gelatin ratio were prepared by a physicalmethod. The effect of mixing ratio on the swelling ratio and the release rate weredetermined. The interaction between the drug and polymer was studied by a FTIR method.Kinetic equations were applied to fit the release data. Experimental results shown that, thedrug release rate is slowed down while PVA's ratio increases. However, out of acomposition limit, an opposite effect on release rate was observed. Kinetic analysissuggests a first-order kinetic mechanism for salicylic acid release from the mixinghydrogel.