▎ 摘　　要

In this report, a nucleic acid sensor has been fabricated via covalent immobilization of Escherichia coli O157:H7 (E. coli) specific probe oligonucleotide sequence, onto graphene oxide modified iron oxide-chitosan hybrid nanocomposite (GIOCh) film. The size of the GIOCh, as determined by dynamic light scattering and TEM, varies from 350 to 300 nm, while the zeta potential for the composite remains near 60 mV at pH 4.0. The prepared GIOCh are electrophoretically deposited onto indium tin oxide (ITO) coated glass substrate, used as cathode, while parallel platinum plate is used as counter electrode. The pDNA immobilized onto GIOCh/ITO electrode has been characterized using scanning electron microscopy; contact angle and Fourier transform infrared spectroscopy. Further, the electrochemical response studies carried out using electrochemical impedance spectroscopy reveals that this nucleic acid sensor exhibits a linear response to complementary DNA in the concentration range of 10(-6)-10(-14) M with a detection limit of 1 x 10(-14) M. Under optimal conditions, this biosensor is found to retain about 90% of the initial activity after 6 cycles of use. (C) 2014 Elsevier B.V. All rights reserved.