Electropolymerization in multilayers of aromatic monomers over graphite electrodes for the development of a biosensor for Chagas disease

Abstract

In this work, the electropolymerization of aniline (ANI), o-aminophenol (OAP), o-hydroxybenzamide (OHBA), and o-aminobenzamide (OABA) monomers was investigated in the formation of monolayers and bilayers over graphite electrodes (GE) by cyclic voltammetry (CV) for the application in initial studies for the development of electrochemical immunosensor for Chagas disease. Electrochemical and morphological characterization studies of the combination of sixteen platforms were carried out. It was observed that the functionalized platforms derived from the monomers ANI, OAP, and OABA presented a cationic character, while the functionalized platforms derived from the OHBA monomer presented an anionic character. Morphological differences between the functionalized platforms and the unmodified electrode were observed through SEM, proving the modification of the GE surface. The results obtained by electrochemical impedance spectroscopy corroborated the CV analyses for the platforms functionalized in the presence of redox probes. The immobilization of an equimolar mixture containing the recombinant antigens JL7, 1F8, and B13 was performed over modified GE via adsorption. During immunosensor response evaluation, we observed a slight increase in charge-transfer resistance (Rct) values of 21%, 63%, 32%, and 68% for non-specific antibodies and a significant increase for specific antibodies with values distinct between the polymeric platforms employed: 338% to POABA, 282% to POAP/POHBA, 183% to POHBA/POABA, and 294% to POHBA/POAP. Thus, the data suggests that the efficacy of antigens immobilization depends on the electrode surface characteristics (anionic or cationic), the presence of the functional groups of the monomers, and the structural and morphological characteristics of the polymer formed.