Highly sensitive electrochemical immunosensor based on graphene-wrapped copper oxide-cysteine hierarchical structure for detection of pathogenic bacteria

We report results of the studies relating to fabrication of the graphene wrapped copper (II) assisted cysteine hierarchical structure (rGO-CysCu, 10 mu m) synthesised using facile, aqueous and environmental friendly conditions. The results of electrochemical impedance spectroscopic investigations indicate that self-assembly of rGO-CysCu molecules onto gold electrode provides a high surface area and high electron transfer rate constant (1.82 x 10(-6) cm/s). Further, an ultrasensitive label-free electrochemical immunosensor for quantitative determination of Escherichia coli O157: H7 (E. coli) has been developed using rGO-CysCu as the sensing layer. Under optimal conditions, the calibration plot pertaining to sensing characteristics of the fabricated immunoelectrode for E. coli O157: H7 was approximately linear in the wide detection range of 10 CFUmL(-1) to 10(8) CFUmL(-1) with a detection limit of 3.8 CFUmL(-1). Moreover, the proposed method was successfully used to differentiate the E. coli O157: H7 cells from the non-pathogenic E. coli (DH5 alpha) and other bacterial cells in the synthetic samples. (C) 2016 Elsevier B.V. All rights reserved.