The improvement of polyaniline glucose biosensor stability using enzyme immobilization from water–organic mixtures with a high content of organic solvent

Abstract

Immobilization of a glucose oxidase (GOD) into Nafion membranes is proposed by suspending the enzyme in a water–ethanol mixture with a high (>90%) ethanol content, mixing with the polyelectrolyte solution, and drying at the target surface. Since Nafion was deposited from its real solution without excessive dissolving with water, the resulting membranes were more uniform and stable. The enzyme suspension in concentrated ethanol solutions were prepared without any prior modifications of the protein. The remaining activity of glucose oxidase after 30-min exposure to such solutions under optimal conditions was up to 100%. The stability of the GOD in these suspensions was higher than in aqueous solution. Potentiometric polyaniline-based biosensor made according to the proposed method of enzyme immobilization showed a several times increased response as compared with enzyme electrodes developed in the traditional way using excessive dilution of Nafion with water. The remaining activity of the enzyme electrode made by GOD immobilization from concentrated organic solvent was 95–100% after several drying–washing cycles.