A novel capacitive biosensor for cholesterol assay that uses an electropolymerized molecularly imprinted polymer

A novel cholesterol biosensor based on capacitive detection has been developed using molecularly imprinted polymers. The sensitive layer was prepared by electropolymerization of 2-mercaptobenzimidazole (2-MBI) on a gold electrode in the presence of cholesterol as a template. Cyclic voltammetry and capacitive measurements were used to monitor the process of electropolymerization. Surface uncovered areas were plugged with 1-dodecanethiol to make the layer dense, and the insulating properties of the layer were studied in the presence of K3Fe(CN)6/K4Fe(CN)6 redox couples and also by the use of AC impedance measurements. The template molecules and the non-bound thiol were removed from the modified electrode surface by washing with an alkaline solution of ethanol. The sensor's linear response range was between 5 and 30 μM, with a detection limit of 0.42 μM. The proposed molecularly imprinted polymer capacitive (MIPC) sensor exhibited good selectivity for cholesterol. The reproducibility and repeatability of the MIPC senor were all found to be satisfactory. The results from sample analysis confirmed the applicability of the MIPC sensor to quantitative analysis.