Gold electrode functionalized by electropolymerization of a cyano N-substituted pyrrole: application to an impedimetric immunosensor

An impedimetric immunosensor based on functionalized electropolymerized layers has been developed. The proposed experimental procedure involves, primarily, the electrogeneration of an N-substituted polypyrrole, carrying terminal cyano groups, on gold electrodes. The latter was characterized by cyclic voltammetric measurements performed in the range 0–0.8 V. Then, immobilization of the antibodies (anti-rabbit IgG) was achieved through electrostatic interactions between the terminal cyano groups of the polymer and the hydroxyl groups of the antibodies. The efficiency of this immobilization method was revealed by both gravimetric and permeation measurements. Impedance measurements have been used to characterize the electrical characteristics of the functionalized electrodes in order to optimize the working conditions of the immunosensor. It appears that, at a bias potential of −1.425 V, the Warburg impedance is negligible and the variation of the impedance caused by specific interaction between immune species can be exploited for sensing purposes, especially at low frequency. Thus, the sensor based on this immobilization method exhibits a good selectivity as well as a large linear dynamic range, from 600 ng ml−1 to 900 ng ml−1.