A Novel Label-Free Amperometric Immunosensor Based on Graphene Sheets-Methylene Blue Nanocomposite/Gold Nanoparticles

Abstract

In this study, a sensitive, label-free amperometric immunosensor based on graphene sheets-methylene blue nanocomposite and gold nanoparticles (GS-MB/GNPs) for the direct determination of chlorpyrifos residues was exploited. To fabricate the immunosensor, GS was first dispersed with chitosan(CS) to obtain a homogeneous solution and then mixed with MB in a ratio of 2:1. The nanocomposite film of GS-MB was dropped on the surface of glassy carbon electrode (GCE) which was first modified by the electrodeposition of GNPs. The stepwise assembly process of electroactive species on electrode surface and the performance of the immunosensor was characterized by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM), respectively. The GS-MB nanocomposite possesses good electrochemical behavior and high binding affinity to the electrode. Furthermore, high surface areas of GS and vast aminos and hydroxyls of CS provide a platform for the crosslinking of antibody. Under optimal conditions, the proposed immunosensor showed a wide linear range from 1 to 500 ng/mL with a detection limit of 0.056ng/mL.The constructed immunosensor exhibited good reproducibility, high specificity, acceptable stability and regeneration performance, which provided a new promising tool for the detection of chlorpyrifos in real samples.