Catalase effects on glucose-sensitive hydrogels

Glucose-sensitive hydrogels (GSHs) responsive to both pH value and glucose concentration have been prepared by polymerizing solutions containing hydro xypropyl methacrylate, (N,N-dimethylamino)ethyl methacrylate, and tetraethy lene glycol dimethacrylate in the mole ratio 70:30:2. Various concentration s of both glucose oxidase (GOx) and catalase were physically immobilized in the hydrogel matrix. The presence of GOx makes the hydrogels glucose-respo nsive, and catalase was added in order to explore its effects on swelling k inetics. In response to pH changes, hydrogels containing varying amounts of catalase show identical swelling kinetics and identical equilibrium degree s of swelling. However, in response to increases in glucose concentration, the rate of GSH swelling is dramatically increased by the presence of catal ase when GOx activity is limited by the amount of oxygen available. In addi tion, catalase improves the enzymatic stability of the GOx by converting hy drogen peroxide to water.