A Novel Electrochemical Genosensor for Specific Detection of xanQ Gene in Escherichia coli Strains in Water

Background: A rapid and specific detection of pathogens is of great importance from public health viewpoint as well as from economic perspectives. Genosensor based on sequence specific detection of Escherichia coli facilitates significant improvements in rapidity and specificity over traditional microbiological methods. Objective: The present study was aimed at identifying a sequence of xanQ genetic markers for designing the DNA sensing probe and fabricating a genosensor using the interdigitated gold electrode (IDE). Methods: A label-free genosensor for E. coli detection in water by a novel nucleic acid sensing probe, URecA1016 is reported. The URecA1016 sensing probe-functionalized gold-interdigitated electrode surface by covalent coupling using 11-Mercaptoundecanoic acid (crosslinker) to develop the electrochemical genosensor. Results: Upon DNA hybridization, the non-Faradaic sensing measurements showed a decreasing capacitance value with 10 min response time at 120 Hz frequency and 10 mV applied potential. The linearity range of the genosensor was between 1 and 1000 pg/mL for DNA of E. coli with a limit of quantification (LoQ) of 1.27 pg DNA/mL of E. coli (equivalent to approximately 150 CFU/mL) at 95% confidence. Whilst the genosensor was E. coli species-specific as has been tested for the detection of E. coli MTCC 3221, E. coli O157:H7 ATCC 43895, E. coli O78:H11 MTCC 723 any cross-reactivity could not be observed with DNA of Shigella flexneri MTCC 9543 and Bacillus subtilis MTCC 736. The capacitance change responses were also recorded and discussed. Conclusion: The URecA1016 sensing probe was found to be specific for the detection of different E. coli species spiked in water. The results obtained in our study demonstrated the possible application potential of genosensor for E. coli detection in real water samples.