IN-VITRO STUDIES ON A NEW METHOD FOR ISLET MICROENCAPSULATION USING ATHERMOREVERSIBLE GELATION POLYMER, N-ISOPROPYLACRYLAMIDE-BASED COPOLYMER

Various materials for the semipermeable membrane for microencapsulatio n of islets, such as alginate complex and agarose, have been used. In this study, a thermoreversible gelation polymer, N-isopropylacrylamide based copolymer was used to make microencapsulated islets and was exa mined in vitro. The polymer has little or no cytotoxicity for human de rmal fibroblasts. The characteristics of viscoelasticity below the sol uble gel transition temperature (SGTT) and of thermoreversibility, the water soluble polymer below the SGTT (22 degrees C) becoming water in soluble upon heating, contributed to simplifying the encapsulation tec hnique. We obtained viable islets at the center of the membrane with a thickness of approximately 20-50 mu m, accounting for a 40% yield of encapsulated islets. Static glucose challenge test with microencapsula ted islets revealed the insulin response to the concentration of gluco se. The insulin concentrations of the culture medium in the microencap sulated islet group were the same as those in a similar free islet gro up up to 42 days. These results indicate that the morphological and fu nctional stability of the new method for microencapsulation may be suf ficient for it to be used for transplantation in diabetic animals.