Electrochemical deposition of gold nanoparticles on graphite rod for glucose biosensing

A biosensor based on glucose oxidase (GOx) immobilized on gold nanoparticles (Au-NPs) electrochemically predeposited on the surface of graphite rod (GR) electrode was developed (GOx/Au-NPs/GR). Main analytical characteristics of this biosensor were determined and compared with those determined using a biosensor setup without Au-NP modification (GOx/GR). The highest analytical signal of GOx/Au-NPs/GR electrode was observed after 13 nm Au-NP deposition on the electrode from 0.8 nmol L−1 solution lasting 20 min, when cyclic voltammetry was performed in the range from 0.0 to +1.0 V vs Ag/AgCl. The best analytical characteristics of the developed biosensor were obtained after 25 mg mL−1 GOx immobilization on the Au-NPs/GR electrode. Analytical signal registered using GOx/Au-NPs/GR electrode was 2.08 times higher in comparison to GOx/GR electrode. The registered currents of both electrodes were linearly dependent on glucose concentration in the range of 0.1-10 mmol L−1. The developed GOx/Au-NPs/GR electrode was characterized by high sensitivity, which was equal to 101.02 μA mM−1 cm−2 in the linear glucose detection range. The limit of detection was 0.083 mmol L−1 with relative standard deviation of 6% for GOx/Au-NPs/GR electrode. This study demonstrates a successful practical exploitation of the developed biosensor in a human serum sample.