Abstract
The direct electrochemistry of glucose oxidase (GOD) adsorbed on a colloidal gold modified carbon paste electrode was investigated. The adsorbed GOD displayed a pair of redox peaks with a formal potential of −(449±1) mV in 0.1 M pH 5.0 phosphate buffer solution. The response showed a surface-controlled electrode process with an electron transfer rate constant of (38.9±5.3)/s determined in the scan rate range from 10 to 100 mV/s. GOD adsorbed on gold colloid nanoparticles maintained its bioactivity and stability. The immobilized GOD could electrocatalyze the reduction of dissolved oxygen and resulted in a great increase of the reduction peak current. Upon the addition of glucose, the reduction peak current decreased, which could be used for glucose detection with a high sensitivity (8.4 μA/mM), a linear range from 0.04 to 0.28 mM and a detection limit of 0.01 mM at a signal-to-noise ratio of 3 σ. The sensor could exclude the interference of commonly coexisted uric and ascorbic acid.
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