▎ 摘　　要

In this article, we present a simple and sensitive electrochemical DNA biosensor based on graphene oxide (GO)/chitosan (CS) hybrid nanocomposites modified glassy carbon electrode (GCE) for detection of Escherichia coli O157:H7 (E.coli O157:H7). The morphology and composition of GO and hybrid nanocomposites were characterized by transmission electron microscope (TEM), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier transform infrared spectrum (FTIR). Cyclic voltammetry investigations indicated that the GO/CS/GCE showed excellent electron transfer ability and good linear relation. Under the optimal hybridization conditions, electrochemical impedance spectroscopy (EIS) responses of ssDNA/GO/CS/GCE biosensor were in linear with the target DNA in the concentration range from 1x10(-14) to 1x10(-8) M with the detection limit as 3.584x10(-15) M (3 sigma). Moreover, differential pulse voltammetry (DPV) studies revealed good specificity and excellent ability of ssDNA/GO/CS/GCE biosensor to distinguish complementary, 1-base mismatched DNA, 2-base mismatched DNA and multi-base mismatched DNA. The developed strategy in this research revealed that the GO/CS modified electrode possess excellent performance for detecting of Escherichia coli O157:H7 DNA.