A polyethylene-g-acrylic acid (PE-g-AA) graft copolymer was prepared via gamma-ray-irradiation-induced postirradiation procedures, and was used as support material for the immobilization of glucose oxidase. Soluble carbodiimides were used as the coupling agent. Reasonable yields were obtained with CMC but not with EDAC, EEDQ, or WRK. A number of factors were studied.
(1) The use of water-soluble carbodiimides as condensing agent was attempted and the optimum condition for coupling glucose oxidase to PE-g-AA was established;
(2) the effect of pH and temperature on the reactivity of native and immobilized glucose oxidase was studied. When exposed to temperatures in excess of 60ยฐC, the immobilized glucose oxidase was less sensitive to thermal inactivation than the native enzyme. The optimum pH value for the performance of the enzyme-immobilized membrane was 5.6. For 200 tests, the response error of glucose sensor was less than 4% and its linear detected range was 0-1000 ppm. The obtained glucoseoxidase-immobilized PE-g-AA membranes were kept in pH 5.6 acetate buffer solution at 4ยฐC. The glucose oxidase activity of the membrane was determined at sevenday intervals. The membranes still have 92% glucose oxidase activity even after eight weeks of storage.