Magnetic electrode-based electrochemical immunosensor using amorphous bimetallic sulfides of CoSnSx as signal amplifier for the NTpro BNP detection.

In this work, by using amorphous bimetallic sulfides of CoSnSxPd as signal amplifier and magnetic material of Fe3O4 @PPyAu as the substrate, we fabricated an electrochemical immunoassay for Nterminal prohormone of brain natriuretic peptide (NTpro BNP). CoSnSx was used as the signal amplifier of the immunosensor for the first time, which was synthesized by fast stoichiometric co-precipitation method. The binary sulfide was identified as an amorphous structure and performed apparent electrochemical behavior. The excellent performance of signal marker was induced by the synergistic effect between SnS2 and cobalt, as well as the loaded Pd nanoparticles (NPs). Both CoSnSx and Pd NPs presented excellent electrocatalytic activity toward H2O2 oxidation. Moreover, the magnetic nanocomposite of Fe3O4 @PPyAu was firmly immobilized on the magnetic glassy carbon electrode (MGCE) by the magnetic force. The magnetic substrate not only performed good electron conductivity, but also improved the stability of the fabricated electrochemical immunosensor. The developed immunosensor for the NTpro BNP detection exhibited a wide linear response (0.1 pg/mL to 50 ng/mL), and low detection limit of 31.5 fg/mL. In addition, the immunosensor held an excellent analysis capability and broad fascinating application for the detection of other biomarkers in medical diagnosis and treatment.