Label‐free, PCR‐free DNA Hybridization Detection of Escherichia coli O157 : H7 Based on Electrochemical Nanobiosensor

A simple and sensitive nanobiosensor was developed for diagnosing label‐free, PCR‐free of rfbE gene in Escherichia coli O157 : H7 real sample. The Au nanoparticles modified electrode (Au nano ME) was prepared by electrodeposition technique. The single‐stranded DNA probes were immobilized through the chemisorptions process on Au nano ME (ssDNA/Au nano ME). Electrochemical impedance spectroscopy (EIS) technique has been used to investigate the hybridization and sensing properties. Using electrochemical impedance spectroscopy (EIS) technique, the charge‐transfer resistance (R ct ) values were raised by immobilization of the DNA probe and after the hybridization with the complementary oligonucleotide for ssDNA/Au electrode from 2.81±0.1 to 7.62±0.2 kΩ and for ssDNA/Au nano ME from 2.58±0.1 to 9.95±0.2 kΩ. The results showed that the immobilization and hybridization of DNA on the Au nano ME increases effectively the nanobiosensor response compared with the Au bare electrode. In addition, the electrochemical DNA biosensor showed a good selectivity toward the detection of the complementary oligonucleotides of the rfbE gene of E. coli O157. The nanobiosensor response showed a linear dynamic range 1.0×10 −13 to 1.0×10 −6 mol L −1 with a detection limit of 9.1×10 −14 mol L −1 and was able to detect E. coli O157 : H7 real sample corresponding to 10 2 cells per ml. Our results suggest that, the nanobiosensor is promising for environmental and clinical applications.