Amperometric immunosensor based on deposited gold nanocrystals/4,4′-thiobisbenzenethiol for determination of carbofuran

In this paper, a novel label-free amperometric immunosensor for the detection of carbofuran residues was developed. The deposited gold nanocrystals (DpAu)/4,4′-thiobisbenzenethiol (DMDPSE) multilayers ({DpAu/DMDPSE}n) membranes were used for modifying Au electrode to fabricate amperometric immunosensor. DpAu/DMDPSE multilayers were modified alternatively to form multiple membranes by layer-by-layer self-assembly technology. The sensitive steps of surface modification were characterized by cyclic voltammetric (CV) and electrochemical impedance spectroscopy (EIS), respectively. The immunoreaction between anti-carbofuran monoclonal antibody and carbofuran directly triggered a signal via different pulse voltammetry (DPV). Under the optimized conditions, a linear relationship between the relative change in peak current of DPV (%ΔI) and the logarithm of carbofuran solution was obtained in the range from 0.1 to 1.0 × 106 ng/mL with a detection limit of 0.06 ng/mL. The advantages of the immunosensor were exhibited in its wider linear range, better reproducibility, stability, selectivity and regeneration. Using lettuces, cabbages, green peppers, tomatoes, Chinese chives and strawberries as model samples, acceptable recovery of 82.0–109.2% was obtained. The proposed method was proven to be a feasible quantitative method for carbofuran analysis, which may open a new door for ultrasensitive detection of carbofuran residues in vegetables and fruits.