A sandwich-type electrochemical immunosensor for ultrasensitive detection of multiple tumor markers using an electrical signal difference strategy

Traditional sandwich-type electrochemical immunosensors can only detect single tumor markers because signal interference occurs when detecting multiple tumor markers. In this work, an electrical signal difference strategy was proposed for the accurate detection of multiple tumor markers. We labeled PdAgCeO 2 mesoporous nanospheres with a carcinoembryonic antigen (CEA) secondary antibody and MnO 2 nanosheets labeled with an alpha-fetoprotein (AFP) secondary antibody. The two electrical signal tags were mixed and incubated on a prepared immunosensor to catalyze H 2 O 2 and generate an electrical signal I 1 (i-t ampere curve). When 2.5 mM ascorbic acid solution (AA) was added to 20 mL of PBS solution at pH = 6.5 for 180 s, an electrical signal I 2 was generated. I 2 was the current response of the CEA antigen concentration, and the electrical signal difference ΔI  =  I 1 – I 2 was the current response of the AFP antigen. Thus, the immunosensor accurately detected the AFP and CEA tumor markers. This method was called the electrical signal difference strategy. The proposed single-use immunosensor detected CEA antigens in a range of 0.001 ng/mL-40 ng/mL, and the detection limit was 0.5 pg/mL; the detection range of the AFP antigen was 0.005 ng/mL-100 ng/mL, and the detection limit was 1 pg/mL. Therefore, this study provides new ideas and strategies for accurate clinical detection of multiple tumor markers.