PH TEMPERATURE-RESPONSIVE POLYMER COMPOSED OF POLY((N,N-DIMETHYLAMINO)ETHYL METHACRYLATE-CO-ETHYLACRYLAMIDE)/

The pH/temperature-induced phase transition of poly((N,N-dimethylamino )ethyl methacrylate (DMAEMA)-co-ethylacrylamide (EAAm)) was investigat ed. Although polyDMAEMA and polyEAAm were reported to exhibit a lower critical solution temperature (LCST) at 50 and 80 degrees C, respectiv ely, a LCST shift from 50 to 4 degrees C was observed with copolymers of DMAEMA with EAAm, and this behavior was quite different at pH 4.0 a nd 7.4. This is due to the formation of hydrogen bonding between DMAEM A and EAAm residues with a hydrophobic contribution to the LCST. To ap ply this polymer system to glucose-controlled insulin release, a molde d matrix consisting of poly(DMAEMA-co-EAAm), glucose oxidase, and insu lin was prepared. This matrix exhibited a rapid change from insolubili ty to solubility when exposed alternately to solutions with ions and a high glucose concentration, resulting in glucose-controlled insulin r elease.