Sandwich-type electrochemical immunoassay based on Co 3 O 4 @MnO 2 -thionine and pseudo-ELISA method toward sensitive detection of alpha fetoprotein.

In this study, a sensitive sandwich-type electrochemical immunosensor was fabricated for the detection of alpha fetoprotein (AFP) based on Co3 O4 @MnO2 -thionine (Co3 O4 @MnO2 -Th) and the screen printing technique. Meanwhile, the pseudo enzyme-linked immunosorbent assay (pseudo-ELISA) method was applied in fabricating the immunosensor. Screen-printed carbon electrode (SPCE) was applied for achieving the detection of AFP. Simultaneously, the amino functionalized Co3 O4 @MnO2 -Th was employed as secondary label and could greatly improve the electrochemical response signal, which was beneficial for detecting AFP. Differential pulse voltammetry (DPV) was applied for the detection of AFP and electrochemical impedance spectroscopy (EIS) confirmed the successful fabrication of the immunosensor. Under optimal conditions, the immunosensor exhibited a linear response toward AFP in the range of 0.001-100 ng/mL, with a low detection limit of 0.33 pg/mL. Simultaneously, the proposed immunosensor displayed acceptable selectivity, excellent stability and well reproducibility. Furthermore, this proposed strategy may open up new ideas and find many potential applications in the detection of other tumor markers.