ABSTRACT
Distinct architectures of layer-by-layer (LbL) films made of carbon nanotubes and gold nanoparticles were investigated to serve as the matrix to immobilize cholesterol oxidase, with which cholesterol could be detected using amperometry. The gold nanoparticles were synthesized by metal reduction stabilized in poly(allylamine hydrochloride) (PAH) providing a stable AuNPs-PAH suspension, while multi-walled carbon nanotubes (CNTs) were functionalized with carboxylic groups to obtain an aqueous suspension. The LbL films were deposited on ITO, with a cushion film of PAH and poly(vinyl sulfonic acid) (PVS). Owing to the synergy between CNTs and AuNPs, the electrode ITO/(PAH/PVS)2 (AuNPs-PAH/CNTs)10 was selected for immobilization of cholesterol oxidase (ChOx). This sensor could detect cholesterol with a limit of detection of 14.8 µmol L-1 and sensitivity of 36.47 (µA cm-2)·(mmol L-1)-1. It was also able to determine cholesterol in egg yolk with a recovery of 97.7%.
