A disposable electrochemical immunosensor for carcinoembryonic antigen based on nano-Au/multi-walled carbon nanotubes–chitosans nanocomposite film modified glassy carbon electrode

In this paper, a disposable electrochemical immunosensor for the detection of carcinoembryonic antigen (CEA) based on Au nanoparticles (AuNPs)/multi-walled carbon nanotubes (MWCNTs)–chitosans (Chits) composite film was developed. MWCNTs–Chits homogeneous composite was first dispersed in acetic acid solution and then the AuNPs was in situ synthesized at the composite. The mixture was dripped on the glassy carbon electrode (GCE) and then CEA antibody (anti-CEA) was immobilized on the resulted modified electrode to construct the immunosensor. The stepwise assembly process of the immunosensor was characterized by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CV and differential pulse voltammetry (DPV) studies demonstrated that the formation of antibody–antigen complexes decreased peak current of [Fe(CN)6]3−/4− redox pair at the AuNPs/MWCNTs–Chits/GCE. The optimization of the pH of supporting electrolyte, the incubation temperature and time were studied in detail. Under optimal conditions, the peak current of DPV of the immunosensor decreased linearly with increasing CEA concentration in two ranges of 0.3–2.5 and 2.5–20 ng mL−1, with a detection limit of 0.01 ng mL−1 (S/N = 3). This electrochemical immunoassay combines the specificity of the immunological reaction with the sensitivity of the AuNPs and MWCNTs amplified electrochemical detection. It would be valuable for diagnosis and monitoring of carcinoma.