Direct electrochemistry of glucose oxidase immobilized on NdPO4 nanoparticles/chitosan composite film on glassy carbon electrodes and its biosensing application

The direct electrochemistry of glucose oxidase (GOx) immobilized on a composite matrix based on chitosan (CHIT) and NdPO(4) nanoparticles (NPs) underlying on glassy carbon electrode (GCE) was achieved. The cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the modified electrode. In deaerated buffer solutions, the cyclic voltammetry of the composite films of GOx/NdPO(4) NPs/CHIT showed a pair of well-behaved redox peaks that are assigned to the redox reaction of GOx, confirming the effective immobilization of GOx on the composite film. The electron transfer rate constant was estimated to be 5.0 s(-1). The linear dynamic range for the detection of glucose was 0.15-10 mM with a correlation coefficient of 0.999 and the detection limit was estimated at about 0.08 mM (S/N=3). The calculated apparent Michaelis-Menten constant was 2.5 mM, which suggested a high affinity of the enzyme-substrate. The immobilized GOx in the NdPO(4) NPs/CHIT composite film retained its bioactivity. Furthermore, the method presented here can be easily extended to immobilize and obtain the direct electrochemistry of other redox enzymes or proteins.