Simple and Effective Procedure for Immobilization of Oxidases onto MnO2-bulk-modified, Screen-printed Carbon Electrodes

Abstract

Nafion(R) film entrapment of oxidases onto the surface of MnO2-(5%, m:m) bulk-modified, screen-printed carbon electrodes was studied taking the inexpensive glucose oxidase as a model enzyme. The Nafion(R)-enzyme film was formed by drop-coating the suspension onto the surface of the electrode. Comparisons weremadeamong biosensors developed by using as-received, neutralized, and diluted (to 1% in methanol, ethanol or phosphate buffer) Nafion(R) in a flow injection (FI) mode. The amperometric response to injections of standard glucose solution was the highest for biosensors produced using neutralized Nafion(R). The effect of enzyme load per electrode (10-1190 mg) was investigated and 50 mg enzyme in the film per electrode was found to produce very good sensitivity as well as to be economical. Good reproducibility was achieved for three different biosensors (RSD of the means = 5.7%). The operational parameters for the glucose biosensor produced with this immobilization procedure were assessed and figures of merit obtained at the selected parameters. It has been observed that the effect of Nafion(R) to repel interfering ions like ascorbate and urate was lacking in this system. A preliminary investigation incorporating a hydrogen peroxide permselective membrane layer prior to enzyme immobilization gave promising result with polyurethane.


South African Journal of Chemistry Vol.57 2004: 1-7