Direct electrochemistry of glucose oxidase and its biosensing to glucose based on the Chit-MWCNTs–AuNRs modified gold electrode

A new glucose biosensor was constructed by immobilizing glucose oxidase (GOD) in the Chitosan (Chit)-Multi-walled carbon nanotubes (MWCNTs)/Gold Nanorods (AuNRs) composite membrane. The Chit-MWCNTs/GOD/AuNRs/gold electrode (GE) displayed a pair of well-defined and reversible redox peaks with the formal potentials (Eθ′) of −0.384 V in 0.1 mol L−1 pH 7.0 PBS. The apparent heterogeneous electron transfer rate constants (ks) of GOD confined to Chit-MWCNTs/AuNRs membrane was evaluated as 11.03 s−1 according to Laviron’s equation. The surface concentration (Γ*) of the electroactive GOD in the film was estimated to be (7.03 ± 0.02) × 10−11 mol cm−2. The electrocatalytic oxidation to glucose of Chit-MWCNTs/GOD/AuNRs/GE was also studied. Its apparent Michaelis–Menten constant for glucose was 1.34 mmol L−1. The experiment results showed that the linear dependence of the electrocatalytic current of the biosensor was from 0.28 to 5.88 mmol L−1, the detection limit of the sensor was 2.06 × 10−5 mol L−1 (S/N = 3), and the obtained sensitivity was 38.2 μA mmol−1 cm−2. Moreover, the biosensor showed rapid response to glucose, good stability and reproducibility.