Planar amperometric enzyme-based glucose microelectrode

Abstract

An amperometric glucose sensor (dimensions 0.8 mm by 3 mm) consisting of a planar three-electrode cell, an enzyme membrane and an outer polyurethane membrane, is described. The transducer is realized using thin-film deposition and lift-off techniques and consist of two Pt electrodes (working and counter) and an Ag/-AgCl reference electrode. It is coupled with an immobilized glucose oxidase membrane and the amount of H 2O 2 produced is measured at 0.7 V. In order to render the sensor response less dependent on the dissovled oxygen concentration, a polyurethane membrane is applied by dip-coating. The sensor response, measured at 37°C in a Ringer solution (ph 7.5) saturated with 5% O 2, is linear up to 40 mM glucose with a sensitivity of 1.8 ± 0.2 nA/mM. The operational lifetime, defined as the time period during which the sensitivity remains constant, is approximately one week. The storage lifetime is more than one month.