Reagentless and label-free voltammetric immunosensor for carcinoembryonic antigen based on polyaniline nanowires grown on porous conducting polymer composite

A reagentless and label-free voltammetric modified electrode was developed for the carcinoembryonic antigen (CEA), an important biomarker for colorectal adenocarcinoma. It is based on the use of a reticular hybrid composite consisting of polyaniline (PANI) nanowires grown on the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) that was doped with an ionic liquid (IL). The composite features excellent electrical conductivity and a porous structure, a high specific surface and inherent redox activity. It was placed on a glassy carbon electrode (GCE) and antibody against CEA was immobilized on its surface. The redox current of PANI, measured typically at 0.16 V (vs. Ag/AgCl) serves as the analytical information. This electrode displays linear range that extends from 0.001 to 10 ng mL−1, with a detection limit as low as 0.7 pg mL−1. It also possesses excellent temporal stability and selectivity.