Determination of carcinoembryonic antigen as a tumor marker using a novel graphene-based label-free electrochemical immunosensor.

In this work, a simple label-free electrochemical immunosensor for the detection of carcinoembryonic antigen (CEA) was developed. At first, the GC electrode was coated with partially reduced graphene oxide (rGO) to form a platform to bind the antibody. After activating the carboxyl groups of rGO through the EDC/NHS linker, the electrode surface was covered with the antibody. Then, the electrochemical behavior of the antibody-modified electrode and the parameters of the interactions of antibody-antigen immune complexes were investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). This immune-complex layer was found to attenuate the electrochemical current which can be used as a good signal to determine the antigen concentration. The proposed immunosensor exhibited a good amperometric response to CEA within a concentration range of 0.1-5 ng mL-1 with a detection limit of 0.05 ng ml-1. Furthermore, the developed method was evaluated for the detection of CEA in the real sample (human blood serum), and the results were comparable with the reference values obtained by the standard enzyme-linked immunosorbent assay (ELISA). Our findings suggest the present immunosensor as a good candidate for application in clinical screening.