Sandwich-type electrochemical immunosensor for CEA detection based on Ag/MoS2@Fe3O4 and an analogous ELISA method with total internal reflection microscopy

In this work, an ultrasensitive electrochemical immunosensor was developed for detecting carcinoembryonic antigen (CEA) based on Ag/MoS2@Fe3O4 and an analogous enzyme linked immunosorbent assay (ELISA) method. The fabrication process was conducted by using 96-well microplate and the detection process was executed on magnetic glassy carbon electrode (MGCE), which was named analogous ELISA method. The technique of total internal reflection fluorescence (TIRF) was firstly employed to verify the feasibility of the proposed method. A sandwich-type strategy was applied for the fabrication of the immunosensor and Ag/MoS2@Fe3O4 was used as label. Simultaneously, Ag nanoparticles (Ag NPs) were applied for modifying the MGCE as sensing platform due to its excellent electroconductivity. Ag/MoS2@Fe3O4 could firmly attached on the surface of MGCE thanks to the magnetic property of Fe3O4. Differential pulse voltammetry (DPV) was applied for the detection of CEA and electrochemical impedance spectroscopy (EIS) confirmed the successful fabrication of the immunosensor. Under optimal experimental conditions, a linear response was achieved in the range of 0.0001-20 ng/mL with a low detection limit of 0.03 pg/mL. Furthermore, the proposed immunosensor exhibited good stability, excellent selectivity and fine reproducibility. This proposed strategy provides a new thought and a potential approach for clinical diagnosis of other tumor markers. (C) 2018 Elsevier B.V. All rights reserved.