Integrating an enzyme-entrapped conducting polymer electrode and a prereactor in a microfluidic system for sensing glucose

Abstract

In this study, the flow injection analysis was applied to the enzyme-entrapped electrode on a chip for sensing glucose. The on-chip microelectrode was fabricated by the standard photolithography in clean-room environment and the microfluidic channel height of 100 mm on the chip was formed by poly(dimethylsiloxane). The conducting polymer, poly(3,4- ethylenedioxythiophene), PEDOT, was electropolymerized to entrap the coexisting glucose oxidase (GOD) by cyclic voltammetry (CV). The amount of enzyme entrapped in the matrix measured spectroscopically was about 0.101 U/cm2. At a flow rate of 10 ml/hr, the working electrode (Pt/PEDOT/GOD, WE1) was set at 0.7 V (vs. Ag/AgCl) and sensing of H2O2 was carried out by injecting samples with various concentrations of glucose (Glu). A linear relationship between the sensing current and the glucose concentration, ranging from 1 to 20 mM, was obtained with a sensitivity of 8 nA mm-2 mM -1. The response time and the recovery time were about 30 and 230 s, respectively. For a single-potential test, the oxidation currents of 0.08 mM ascorbic acid (AA) and a blend of 0.08 mM AA and 10 mM Glu reached 31.3% and 145.5%, respectively, when compared with the oxidation current of 10 mM Glu alone. However, when a pre-reactor (WE2) was set at the same potential (0.7 V) before the main enzyme integrated electrode (WE1), the oxidation current for the above mixed solution reached 99.6% of the original one. ? 2008 Wiley-VCH Verlag GmbH & Co. KGaA.