Study On The Fabrication Of Novel Matrix-based Enzyme Electrode And The Direct Electrochemistry

Electrochemical biosensors based on the direct electron transfer between redox enzymes and electrodes have high sensitivity and selectivity. They also have potential applications in biomedical diagnostics and environment monitoring. In order to achieve the direct electron transfer between enzymes and electrodes, improve the direct electron transfer efficiency, and obtain high performance electrochemical biosensors, the high surface coverage of enzymes on the electrode, the maintenace of the bioactivity and electroactivity of enzymes, and the suitable orientation of enzymes are the crutial factors that influnce the perpormance of electrochemical biosensors.From the view of the bioactivity and electroactivity of enzymes, we fabricate two kinds of immobilization matrials that are suitable for the maintenace of enzyme activity. Also we study the direct electrochemistry and electro-catalytical performance of the immobilized enzymes. The details are as follows:1. Immobilizing horseradish peroxidase (HRP) using the low molecular weight gelThe ternary system of dodecylpyridinium bromide (DDPB)/acetone/H20with appropriate composition can form a gel spontaneously and the gel is stable in hydrophobic ionic liquid1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6). Based on the gelation phenomenon we observed previously, the low molecular weight gelator (LMWG) was first tried to immobilize HRP on the glassy carbon electrode (GCE). The direct electrochemistry of the HRP-gel modified GCE (HRP-gel/GCE) in [Bmim]PF6shows a pair of well-defined and quasi-reversible redox peaks with the heterogeneous electron transfer rate constant (î–¹) being14.4s-1. This indicates that the direct electron transfer between HRP and GCE is fast. The HRP-gel/GCE is stable and reproducible. Also the electrode exhibits good electrocatalytic effect on the reduction of trichloroacetic acid (TCA), showing good promise in bioelectrocatalysis.2. Glucose oxidase entrapped in a carbon ionic liquid pasteWe fabricated a carbon ionic liquid electrode (CILE) by mixing N-octylpyridinium hexafluorophosphate (OPPF6) and graphite powder. By drop casting, we immobilized glucose peroxdase (GOD) on the CILE. The direct electrochemistry of the Nafion/GOD/CILE has a pair of well-defined and quasi-reversible redox peaks with Epa. and Epc of-0.358V and-0.402V respectively.The heterogeneous electron transfer rate constant (ks) is2.34s-1indicating that the direct electron transfer between GOD and CILE is fast. In addition, the enzyme electrode is stable and reproducible; also it has electrocatalytic effect on the oxidation of glucose.