Sandwich-type electrochemical immunosensor using dumbbell-like nanoparticles for the determination of gastric cancer biomarker CA72-4.

A novel and sensitive nonenzymatic sandwich-type electrochemical immunosensor for the detection of gastric cancer biomarker CA72-4 was fabricated using dumbbell-like PtPd-Fe3O4 nanoparticles (NPs) as a novel kind of label. The signal amplification strategy, using the synergetic effect present in PtPd-Fe3O4 to increase the reduction ability of the NPs toward H2O2, improved the sensitivity of the immunosensor. The immunosensor was constructed by modifying glassy carbon electrode with reduced graphene oxide-tetraethylene pentamine (rGO-TEPA) for effective immobilization of primary anti-CA72-4 antibody (Ab1). Secondary anti-CA72-4 antibody (Ab2) was adsorbed onto the PtPd-Fe3O4 NPs. The proposed immunosensor displayed a wide linear range (0.001-10 U/mL) with the low detection limit (0.0003 U/mL). The immunosensor was evaluated for serum samples, receiving satisfactory results. Therefore, the immunosensor possesses excellent clinical value in cancer screening as well as convenient point-of-care diagnostics.