Bienzymatic glucose biosensor based on direct electrochemistry of cytochrome c on gold nanoparticles/polyaniline nanospheres composite

Gold nanoparticles (GNPs) assembled polyaniline nanospheres (PANS) composite were prepared by noncovalent strategy. Cytochrome c (Cyt c) was electrostatically adsorbed on the GNPs/PANS modified electrode. The direct electron transfer (DET) between Cyt c and GNPs/PANS modified electrode was investigated. Cyt c shows a couple of quasi-reversible and well-defined cyclic voltammetry (CV) peaks with a formal potential (E0′) of −0.27 V (versus Ag/AgCl) in pH 7.0 phosphate buffer solution (PBS). The Cyt c/GNPs/PANS modified electrode gives an improved electrocatalytic activity toward the reduction of hydrogen peroxide (H2O2). The catalysis currents increase linearly to the H2O2 concentration in a wide range of 0.01–2.4 mM with a correlation coefficient 0.998. After immobilized glucose oxidase (GOD) on the Cyt c/GNPs/PANS modified electrode by Nafion polymer, a bienzymatic glucose biosensor was further prepared for sensitive detection of glucose. The amperometric detection of glucose was assayed by potentiostating the bienzymatic electrode at −0.2 V versus Ag/AgCl to reduce the enzymatically produced H2O2 with minimal interference from the coexisting electroactive compounds. The proposed glucose biosensor exhibits good response performance to glucose with a wide linear range from 0.01 to 3.2 mM with a correlation coefficient of 0.997. The electrode has high sensitivity of 63.1 μA mM−1 cm−2 and a detection limit 0.01 mM at the signal-to-noise ratio of 3. Moreover, the glucose biosensor possesses good stability and reproducibility.