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

Graphene wrapped copper (II) assisted cysteine hierarchical structures as sensing layer for ultrasensitive label-Free Electrochemical Immunosensor for detection of Escherichia coli O157:H7 in water. [Display omitted] •Facile and eco-friendly synthesis of rGO-CysCu hierarchical structures.•The thin structure of the GO exhibit higher electro-chemical performance as sensing layer.•Fabricated immunosensor shows high selectivity and sensitivity for E. coli O157:H7 detection.•The rGO-CysCu based immunosensor can be used to differentiate the E. coli O157:H7 cells from the non-pathogenic E. coli (DH5α) and other bacterial cells in synthetic samples. We report results of the studies relating to fabrication of the graphene wrapped copper (II) assisted cysteine hierarchical structure (rGO-CysCu, 10μm) 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 (1.82×10−6cm/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 10CFUmL−1 to 108CFUmL−1 with a detection limit of 3.8CFUmL−1. Moreover, the proposed method was successfully used to differentiate the E. coli O157: H7 cells from the non-pathogenic E. coli (DH5α) and other bacterial cells in the synthetic samples.