Sandwich-type amperometric immunosensor using functionalized magnetic graphene loaded gold and silver core-shell nanocomposites for the detection of Carcinoembryonic antigen

Herein, a novel and sensitive sandwich-type electrochemical immunosensor was fabricated for quantitative detection of carcinoembryonic antigen (CEA). In order to construct the base of the immunosensor, the gold nanoparticles (Au NPs) were immobilized on the surface of bare glassy carbon electrode (GCE) through electrochemical reduction of HAuCl4 solution. The electrodeposited gold nanoparticles (D-Au NPs) not only effective improve immobilization of primary anti-CEA antibody (Ab(1)) but also accelerate the electron transfer on the electrode interface due to the high specific surface area, good biocompatibility and superior electrical conductivity. Moreover, the amino functionalized magnetic graphene loaded gold and silver core-shell nanoparticles to adsorb nickel ion (GS-Fe3O4/Au@Ag/Ni2+), which were used as a novel label to load the secondary anti-CEA antibody (Ab(2)). The resultant nanocomposites possess high specific surface area, excellent electrochemical property, good biocompatibility and superior auxiliary catalytic activity due to the synergetic effect. The signal amplification strategy, using the synergetic effect present in Au@Ag/Fe3O4-GS/Ni2+ to improve immobilization of Ab(2) and increase the reduction ability of the nanocomposites towards H2O2, improved the sensitivity of the immunosensor. Under the optimal conditions, a linear relationship between current signals and the concentrations of CEA was obtained in the range from 0.1 pg/mL to 100 ng/mL and the detection limit of CEA was 0.0697 pg/mL (signal-to-noise ratio of 3). Furthermore, the as-proposed immunosensor showed excellent performance in detection of human serum samples. The results suggest that the proposed immunosensor will be promising in the diagnostics application for accurately quantitative detection of CEA.