Direct Electron Transfer of Glucose Oxidase and Glucose Biosensor Based on Nano-structural Attapulgite Clay Matrix

The direct electrochemistry of glucose oxidase (GOD) was achieved based on the immobilization of GOD on a natural nano-structural attapulgite (ATP) clay film modified glassy carbon (GC) electrode. The immobilized GOD displayed a pair of well-defined quasi-reversible redox peaks with a formal potential (E-0') of -457.5 mV (vs. SCE) in 0.1 mol.L-1 pH 7.0 phosphate buffer solution The peak Current was linearly dependent on the scan rate, indicating that the direct electrochemistry of GOD in that case was a surface-controlled process. The immobilized glucose oxidase could retain bioactivity and catalyze the oxidation of glucose in the presence of ferrocene monocarboxylic acid (FMCA) as a mediator with the apparent Michaelis-Menten constant K-m(app) of 1.16 mmol.L-1. The electroacid catalytic response showed a linear dependence on the glucose concentration ranging widely from 5.0 x 10(-6) to 60 x 10(-4) mol.L-1 (with correlation coefficient of 0.9960) This work dernonstrated that the nano-structural attapulgite clay was a good candidate material for the direct electrochemistry of the redox-active enzyme and the construction of the related enzyme biosensors The proposed biosensors were applied to determine the glucose in blood and urine samples with satisfactory results