Electrochemical detection of cholesterol based on competitive host-guest recognition using a β-cyclodextrin/poly(N-acetylaniline)/graphene-modified electrode

A sensitive and selective electrochemical approach for cholesterol sensing based on a competitive host-guest recognition between beta-cyclodextrin (beta-CD) and a signal probe (methylene blue)/target molecule (cholesterol) using a beta-CD/poly(N-acetylaniline)/graphene (beta-CD/PNAANI/Gra)-modified electrode was developed. Due to the host-guest interaction, MB molecules can enter into the hydrophobic inner cavity of beta-CD, and the beta-CD/PNAANI/Gra modified glassy carbon electrode displays a remarkable anodic peak. In the presence of cholesterol, a competitive interaction to beta-CD occurs and the MB molecules are displaced by cholesterol. This results in a decreased oxidation peak current of MB as MB is a well known redox probe and hence can be easily detected using the differential pulse voltammetery technique. A linear response range of 1.00 to 50.00 mu M for cholesterol with a low detection limit of 0.50 mu M (S/N = 3) was obtained by using the indirect method. The proposed method could be successfully utilized to detect cholesterol in serum samples, and may be expanded to analysis of other non-electroactive species. Besides, the host-guest interaction between cholesterol and beta-CD was studied by molecular modeling calculations, which revealed that the complexation could reduce the energy of the system and the complex of 2 : 1 host-guest stoichiometry had the lowest DE value of -10.45 kcal mol(-1). The molecular docking studies suggested that hydrogen bonding, electrostatic interactions, and hydrophobic interactions should be the major driving forces for the formation of the inclusion complex.