Switching biomimetic hydrogels

We propose a new strategy for precise, rapid, quantitatively predictable and revers-ible on{o ¬ regulation of enzymatic reactions. Speci cally, we report reversible photo and pH-switchable hydrolytic activity of a chymotrypsin mimic. The switching-o¬ of mimic activity when exposed to UV irradiation is a consequence of deswelling of the hydrogel that results in a 25-fold decrease in the di¬usivity of the substrate in the hydrogel. The hydrolytic activity of the enzyme mimic can also be switched on/o ¬ in response to pH. Unlike native chymotrypsin, which is irreversibly deacti-vated, the activity of the mimic is reversible and also more stable in hostile environ-ments. A reaction{di¬usion analysis of the problem predicts the course of switching quantitatively