A layer-by-layer assembled and carbon nanotubes/gold nanoparticles-based bienzyme biosensor for cholesterol detection

A bienzyme biosensor for the detection of cholesterol, based on functionalized carbon nanotubes (CNTs) was fabricated through layer-by-layer (LBL) assembly technique. Being wrapped with cationic poly(allylamine hydrochloride) (PAH), the nanocomposite, multiwalled carbon nanotubes (MCNTs) mixed with gold nanoparticles (GNPs) was water soluble and positively charged. Based on reliably electrostatic interaction, bienzyme biosensor was then fabricated by LBL assembly of the positively charged nanocomposite and the negatively charged enzymes, horseradish peroxidase (HRP) and cholesterol oxidase (ChOx). The fabricated process and the electrochemical behaviors of the biosensor were investigated by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Under the optimal conditions, the bienzyme biosensor obtained the linear range from 0.18 to 11 mM, with a detection limit of 0.02 mM. The proposed biosensor exhibited good sensitivity, stability, and controllability for the detection of cholesterol.