Strategies for decreasing ascorbate interference at glucose oxidase-modified poly(o-phenylenediamine)-coated electrodes

Abstract

Monitoring glucose using biosensors in biological systems is complicated by the presence of reducing agents such as ascorbic acid (AA). This is particularly so in brain extracellular fluid (ECF), where glucose concentrations may be as low as 1 mmol l^–1 and AA levels are approximately 500 µmol l^–1. Since glucose oxidase-modified poly(o-phenylenediamine)-coated Pt (Pt/PPD/GOx) electrodes show good stability in vivo, glucose sensitivity and AA-blocking properties, attempts were made to improve the latter characteristic further by two distinct strategies: incorporating non-enzyme protein into the polymer film and underlaying the polymer with a lipid coat. Both tactics significantly decreased interference by AA without changing the sensitivity to glucose, the lipid modification being the more effective. The current ratio I_Gluc/I_AA for 1 mmol l^–1 glucose and 500 µmol l^–1 AA for the best 50% of the lipid-modified Pt/PPD/GOx electrodes was approximately 30:1, indicating that these sensors are well suited for monitoring brain glucose in vivo.