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 β-cyclodextrin (β-CD) and a signal probe (methylene blue)/target molecule (cholesterol) using a β-CD/poly(N-acetylaniline)/graphene (β-CD/PNAANI/Gra)-modified electrode was developed. Due to the host–guest interaction, MB molecules can enter into the hydrophobic inner cavity of β-CD, and the β-CD/PNAANI/Gra modified glassy carbon electrode displays a remarkable anodic peak. In the presence of cholesterol, a competitive interaction to β-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 μM for cholesterol with a low detection limit of 0.50 μM (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 β-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 ΔE 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.