Amperometric biosensors based on gold nanoparticles-decorated multiwalled carbon nanotubes-poly(diallyldimethylammonium chloride) biocomposite for the determination of choline

A novel amperometric choline biosensor based on the nanocomposite film composed of choline oxidase (ChOx), multi-wall carbon nanotubes (MWCNTs), gold nanoparticles (GNp) and poly(diallyldimethylammonium chloride) (PDDA) was developed for the specific detection of choline. GNp-decorated MWCNTs (MWCNTs–GNp) was synthesized by a classical chemical method, and GNp was attached on MWCNTs through the specific interaction between –SH and Au. The enzyme ChOx would be attached to the MWCNTs–GNp matrix and also be adsorbed electrostatically with PDDA which was employed not only as a dispersant but also a binder material. The microscopic structure and composition of the synthesized MWCNTs–GNp were characterized by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX), and properties of the resulting choline biosensors were monitored by electrochemical measurements. Taking the sensitivity and selectivity into consideration, 0.35 V versus Ag/AgCl was selected to detect choline. The resulting biosensor exhibited a wide linear range of 0.001–0.5 mM choline, with a remarkable sensitivity of 12.97 μA/mM, a detection limit of 0.3 μM estimated at a signal-to-noise ratio of 3 and fast response time (within 7 s). Moreover, it showed good reproducibility, anti-interferant ability and long-term stability. This work presented a feasible approach for further research in biosensing and other surface functionalizing.