A label-free amperometric immunosensor for the detection of carcinoembryonic antigen based on novel magnetic carbon and gold nanocomposites

In this work, a novel label-free electrochemical immunosensor was developed for the quantitative detection of carcinoembryonic antigen (CEA). To this end, gold nanoparticle (Au NP) functionalized magnetic multi-walled carbon nanotubes (MWCNTs-Fe3O4) were prepared and applied to lead ion (Pb2+) adsorption. Because of the synergetic effect present in Pb2+@Au@MWCNTs-Fe3O4, they show better electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2) than MWCNTs, MWCNTs-Fe3O4 or Au@MWCNTs-Fe3O4. Featuring a large specific surface area, good biocompatibility and excellent electrical conductivity, Pb2+@Au@MWCNTs-Fe3O4 were used as transducing materials to achieve efficient conjugation of capture antibodies and signal amplification of the proposed immunosensor. Cyclic voltammetry and the amperometric i-t technique were used to record the change of electrochemical signal when the electrodes were modified with different concentrations of CEA. Under optimal conditions, the label-free immunosensor exhibited a wide linear range from 5 fg mL(-1) to 50 ng mL(-1) with a low detection limit of 1.7 fg mL(-1) for CEA. The proposed immunosensor displays high electrochemical performance with good reproducibility, selectivity and stability, and has great potential in clinical and diagnostic applications.