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 mu A/mM, a detection limit of 0.3 mu M 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. (C) 2010 Elsevier B.V. All rights reserved.