Detection of E. coli O157:H7 DNA by a novel QCM biosensor coupled with gold nanoparticles amplification

In recent years, quartz crystal microbalance (QCM) plays an important role in many biological detections, and the enhancement of a single strain DNA probe linked to the sensor surface is of crucial importance in DNA molecule recognition. By means of nanogold modification and mass amplification, a QCM biosensor for Escherichia coli O157:H7 DNA detection was explored and developed in this work. As a suitable surfactant, 1,6-Hexanedithiol was introduced onto the Au surface of QCM, then self-assembled to provide a thioled interface for the inner goldnano immobilization. Based on the Au-SH binding mechanism, thiolated single-stranded DNA (ssDNA) probes which was specific to E. coli O157:H7 eaeA gene would link to the nanoparticle-modified electrode surface. The hybridization was induced by exposing the ssDNA probe to the complementary target DNA, but the frequency change caused by the captured target DNA was negligible. In order to amplify the signal, outer nanogold as the mass enhancer were applied to combine with the target DNA by the biotin-avidin system. The electrochemical techniques, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), are adopted to manifest and character each step, which supplied some reasonable and powerful supports for the frication and detection of this QCM biosensor. The target DNA corresponding to 2.0 times 10³ colony forming unit (CFU)/ml E. coli O157:H7 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. In order to attract more attention, this DNA biosensor should be combined with some micro- and nano-fabrication techniques to realize more promising and pratical applications, and more attention should be focused on the further improvement of the sensitivity and the shorten of analysis time.