Dual mode competitive electrochemical immunoassay for B-type natriuretic peptide based on GS/SnO2/polyaniline-Au and ZnCo2O4/N-CNTs

A sensitive dual mode competitive electrochemical immunosensor for the detection of B-type natriuretic peptide (BNP) was successfully fabricated, which based on differential pulse voltammetry (DPV) and amperometric i-t curve response modes. Polyaniline (PAN) and tin dioxide (SnO 2 ) were loaded on graphene sheets (GS), which could effectively promote the electron transfer process, thereby amplifying the current signal and increasing the sensitivity of the immunosensor. To promote biocompatibility, gold nanoparticles (Au) were incorporated on GS/SnO 2 /PAN (GS/SnO 2 /PAN-Au). GS/SnO 2 /PAN-Au complex was gotten to act as the platform which could provide a clearly DPV signals. N-doped carbon nanotubes (N-CNTs) embellished by ZnCo 2 O 4 quantum dots (ZnCo 2 O 4 /N-CNTs) with excellent catalytic properties for the reduction of H 2 O 2 was gotten to act as the label of the antibody-BNP (Ab), providing an obviously current signal through amperometric i-t curve method. A large quantity of BNP could be stable loaded in the modified electrode via GS/SnO 2 /PAN-Au with excellent electrical conductivity and good biocompatibility , which could compete with target-BNP to combine Ab that labelled by ZnCo 2 O 4 /N-CNTs. Under the optimum conditions, the immunosensor exhibited remarkable analytical performance of a linear range from 0.01 pg/mL to 1 ng/mL with a detection limit of 3.4 fg/mL for quantitative detection of BNP (S/N = 3). This method was able to become a universal strategy for other biological detection.