A sensitive label-free amperometric CEA immunosensor based on graphene-nafion nanocomposite film as an enhanced sensing platform.

A novel approach to fabricate a label-free amperometric immunosensor for the detection of carcinoembryonic antigen (CEA) was described. Herein, methylene blue (MB), gold nanoparticles (AuNPs) and carcinoembryonic antibody (anti-CEA) were layer-by-layer assembled on the graphene-Nafion nanocomposite film-modified electrode by means of a self-assembling technique and the opposite-charged adsorption. Subsequently, the stepwise self-assembling procedure of the immunosensor was further characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The factors influencing the performance of the resulting immunosensor were studied in detail. The developed procedure showed improved features, including larger amount and higher immunoactivity of the immobilized antibody and repeatable regeneration of the sensor, as well as direct, rapid and simple determination for the antigen without multiple separation and labeling steps. The immunosensor could detect the target protein in a range of 0.5 to 120 ng/mL with a limit of 0.17 ng/mL (at 3σ). Finally, the immunosensing system was evaluated on several clinical samples. Analytical results were found to be in satisfactory agreement with those detected by the enzyme-linked immunosorbent assay (ELISA) method, indicating that this new method was a promising alternative tool for clinical diagnosis.