Modulated degradation of dextran hydrogels grafted with poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) in response to temperature

Abstract

Dextran hydrogels grafted with poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) were prepared, and their enzymatic degradation was examined at different temperatures. Although swelling ratios for the hydrogels are constant in a wide range of temperature, there is a drop of transmittance of the hydrogels in the swollen state in relation to the lower critical solution temperature of poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide). Temperature-dependent enzymatic degradation was observed in these hydrogels to depend on the molecular weight of the grafts. The degradability of the hydrogel with shorter grafts is independent of temperature. In contrast, the degradability of the hydrogel with longer grafts increases with increasing temperature. Such a modulated degradation of hydrogels is considered to be due to a change in the entanglement between the grafted chain and dextran network by the hydration-dehydration behavior of the grafts.