Amperometric Choline Biosensor Based on Dispersion of Multi-walled Carbon Nanotubes in Poly(diallyldimethylammonium chloride) via Layer-by-Layer Assembly Technique

Poly(diallyldimethylammonium chloride) (PDDA) was chosen to disperse multi-walled carbon nanotubes(MWCNTs) to prepare the stable PDDA-MWCNTs aqueous dispersion. Then, the positively charged PDDA-MWCNTs composite and negatively charged choline oxidase(ChOx) were employed to fabricate multi-layer films on platinum(Pt) electrodes by layer-by-layer self-assembly technique, the anti-interferential film of Nafion was dropped at the end of the last multilayer films. The results showed that MWCNTs were evenly dispersed within the PDDA films and the multilayer films of (PDDA-MWCNTs) could improve the catalytic current response to choline significantly with the increased number of the multilayer films. The optimum assembly number was 6. The choline biosensor fabricated showed good linear correlation from 5 x 10(-6) - 2.5 x 10(-4) mol/L with a detection limit of 2 x 10(-6) mol/L(S/N = 3), and the sensitivity was 21.97 mA/mol with a response time of 6.6 s, the RSD was less than 5% (n = 3). Moreover, the biosensor exhibited an excellent anti-interferential property and a good stability.