A glucose biosensor based on direct electron transfer of glucose oxidase immobilized onto glassy carbon electrode modified with nitrophenyl diazonium salt

This study reports a novel, simple and fast approach for construction of a highly stable glucose biosensor based on the immobilization of glucose oxidase (GOx) onto a glassy carbon electrode (GCE) electrografted with 4-aminophenyl (AP) by diazonium chemistry. Aminophenyl was used as cross-linker for covalent attachment of glucose oxidase to the electrode surface. Cyclic voltammograms of the GOx-modified GCE in phosphate buffer solution exhibited a pair of well-defined redox peaks, attesting the direct electron transfer (DET) of GOx with the underlying electrode. The proposed biosensor could be used to detect glucose based on the consumption of O2 with the oxidation of glucose catalyzed by GOx and exhibited a wide linear range of glucose from 0.05 mM to 4.5 mM and low detection limit of 10 μM. The surface coverage of active GOx, heterogeneous electron transfer rate constant (ks) and Michaelis-Menten constant (KM) of immobilized GOx were 1.23 × 10−12 mol cm−2, 4.25 s−1 and 2.95 mM, respectively. The great stability of this biosensor, technically simple and possibility of preparation at short period of time make this method suitable for fabrication of low-cost glucose biosensors.