Highly sensitive amperometric cholesterol biosensor based on Pt-incorporated fullerene-like ZnO nanospheres

A highly sensitive amperometric biosensor based on Pt-incorporated fullerene-like ZnO hybrid nanospheres has been investigated. Pt-ZnO nanospheres (PtZONS) with diameters in the range 50-200 nm have been successfully synthesized by electrodeposition on a glassy carbon electrode (GCE). The Pt nanoparticles in ZnO nanospheres have been identified with high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS). The doped Pt nanoparticles demonstrate the abilities to electrocatalyze the oxidation of hydrogen peroxide and substantially raise the response current. The sensitivity of the PtZONS/GCE to hydrogen peroxide is 147.8 μA μM^-1 cm^-2, which is much higher than that of a conventional electrode. The PtZONS/GCE was functionalized with cholesterol oxidase (ChOx) by physical adsorption. The enzyme electrode exhibits a very high and reproducible sensitivity of 1886.4 mA M^-1 cm^-2 to cholesterol with a response time less than 5 s and a linear range from 0.5 to 15 μM. Furthermore, it has been revealed that the biosensor exhibits a good anti-interference ability and favorable stability over relatively long-term storage (more than 5 weeks). All these results strongly suggest that the PtZONS not only enhance the sensitivity to cholesterol but also help to eliminate the interference at low applied potential.