Assessment of the interaction between a synthetic epitope of troponin C and its specific antibody using a label-free faradaic impedimetric immunosensor and α-Keggin silicotungstic heteropolyacid as a redox probe

The development of an immunosensor for the direct probing of the interaction between a cysteine-modified synthetic peptide, which corresponds to the epitope cTnC-89–98 of troponin C, and its specific antibody is described. Following immobilization of the peptide onto gold electrodes through the formation of a self-assembled monolayer, the alteration of the interfacial properties of the electrodes upon peptide–antibody interaction was traced by faradaic electrochemical impedance spectroscopy (EIS) using a silicotungstic heteropolyacid, H4SiO4·12WO3, as a redox probe. The electrochemical behaviour of the redox probe was evaluated with cyclic voltammetry and EIS. The effect of milk protein or 4-mercaptophenol, which was used as post-blocking agents, on the performance of the immunosensor, was investigated. Treatment with 4-mercaptophenol resulted in immunoeffective electrodes that successfully tested in anti-serum samples. An optimum dilution ratio of the samples, where the effect of the matrix on the measuring signal is negligible, was also determined.