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A DNA piezoelectric biosensing method for real-time detection of E. coli O157:H7 in a circulating-flow system was developed in this study. The thioled surface of the Au electrode could be immobilized by many inner Au nanoparticles, then more thiolated single-stranded DNA (ssDNA) probes which was specific to E. coli O157:H7 eaeA gene could be fixed through Au-SH bonding. The hybridization was induced by exposing the ssDNA probe to the complementary target DNA, then resulted in the mass change and corresponding frequency shifts ( Af ) of the QCM. The outer avidin-coated Au nanoparticles could combine with the target DNA to increase the mass. The inner and outer Au nanoparticles with different diameters would play the "signal amplifier" role at different layer for improving the detection limit and sensitivity. The electrochemical techniques, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), are adopted to demonstrate and character each treatment. The target DNA corresponding to 2.0 X 103 colony forming unit (CFU)/ml E. coli 0157:H7 cells can be detected by this biosensor, so it is practical to develop a sensitive and effective QCM biosensor for pathogenic bacteria detection based on specific DNA analysis.
Date of Conference: 8-11 July 2007