A reagentless amperometric biosensor based on the coimmobilization of horseradish peroxidase and methylene green in a modified zeolite matrix

A new biosensor for the amperometric detection of hydrogen peroxide was developed based on the coimmobilization of horseradish peroxidase (POD) and methylene green on a zeolite modified glassy carbon electrode without the commonly used bovine serum albumin - glutaraldehyde. The large specific surface area of such a zeolite matrix resulted in high enzyme and mediator loading. The intermolecular interaction between the enzyme and the zeolite was investigated using FT-IR Cyclic voltammetry and amperometric measurement demonstrated that methylene green coimmobilized with POD in this way displayed good stability and could efficiently shuttle electrons between immobilized enzyme and the electrode. Due to the hydrophilic character of the zeolite the soluble enzyme and methylene green can be retained in the zeolite film, greatly improving the stability of the sensor. Electrocatalytic reduction of H2O2 at the electrode was evaluated with respect to solution pH, temperature and operating potential. The sensor exhibited high sensitivity and could be used for more than two months. (C) 1999 Elsevier Science B.V. All rights reserved.