以普魯士藍/聚二氧乙烯噻吩複合薄膜製備軟性酵素電極與其生物感測應用研究

Abstract

This study aims to develop a flexible, cost-effective but highly durable and sensitive amperometric glucose sensor for real-time monitoring of blood sugar and cellulose degradation, respectively. To this purpose, we investigated the use of a novel organic/inorganic bilayer, poly(3,4-ethylenedioxythiophene) (PEDOT)/Prussian blue (ferric hexacyanoferrate, namely PB), as an enhanced immobilization layer of glucose oxidase (GOD) on a screen printed carbon electrode. To assemble the amperometric glucose sensor, a carbon paste electrode (active area = 0.28 cm2) was screen-printed onto a flexible polyester (PET) substrate at first. Then a PB thin film was electrodeposited on the carbon paste electrode as a solid mediator to carry out the electrocatalysis of hydrogen peroxide, a byproduct indicating the glucose oxidation. Subsequently, a thiophene-based conducting polymer thin film, PEDOT, was grown electrochemically on the PB/carbon paste electrode in the presence of both 3,4-ethylenedioxythiophene monomers and GOD molecules. As a consequence, glucose oxidase molecules were entrapped in the PEDOT matrix atop the PB/carbon paste electrode, and an amperometric glucose sensor was thus fabricated. Before using, the sensor was stored in a phosphate buffer, pH 7.4 at 4 oC. In principle, when contacting an analyte solution containing glucose such as a serum sample or a degraded polysaccharide mixture, the GOD molecules inside the PEDOT matrix will specifically oxidize glucose, in the presence of oxygen, to gluconic acid and hydrogen peroxide. Then hydrogen peroxide will penetrate through the PEDOT layer and react with the solid mediator PB, which finally shuttles electrons to the carbon electrode and yields a cathodic current in response to hydrogen peroxide and thereby to glucose. Accordingly, our amperometric sensing experiment was performed by applying a constant potential of -0.1 V vs. Ag/AgCl, and the sensor was tested with a dilution series of glucose solutions in the presence of phosphate buffer, pH 7.4. With flow-injection analysis (FIA) and a sensing potential at -0.1 V vs. Ag/AgCl, the flexible biosensor exhibited a response of < 40 sec, a dynamic range from 100 uM to 30 mM and a sensitivity of 2.1 uA cm-2 mM-1. Also, the biosensor yielded highly reproducible current signals (RSD = 2.54%) and retained ca. 82% of the glucose sensing response after one-month storage at 4 oC. Furthermore, not only detection of cellulose saccharification product but also quantification of the sugar content of a serum was demonstrated successfully by showing high accuracy (RSD = 8.37%) and low interference. Therefore, we consider this new design of glucose sensor based on the PEDOT/PB bilayer is not only novel from the chemistry aspect but also promising for both bioenergy and biomedical applications.