Research On The Piezoelectric Immunosensor Based On Gold Nanoparticles And SPA For The Detection Of E.coli O157:H7

With the continuous outbreak of foodborne diseases, the problems of food safety have become a great challenge and threat to common healthy issues. One of the key solutions to this problem is to establish a system, which could accomplish a fast and sensitive detection of foodborne microorganism, so as to avoid the loss of human life and assets. In this essay, a construction approach of piezoelectric immunosensor based on gold nanoparticles and SPA, as well as detection effect on E.coli O157:H7, was investigated. The explorary research on application of nanoparticles in biosensor aimed to improve the comprehensive function of piezoelectric immunosensor. The main contents and results are as follows:(1) Piezoelectric immunosensor based on gold nanoparticles and SPA was constructed. The cleaning method of the QCM gold electrode was discussed and the stability test of the electrode was carried out; the optimal method and time was selected to obtain a best effect of the HDT self-assembled procedure; the gold nanoparticles were prepared and then their sizes and shapes were evaluated by means of TEM and UV-visible spectrophotometry, besides, the relationship between the quantity of gold nanoparticles immobilized on the QCM gold electrode and their frequency response was studied theoretically.(2) The dipping-drying method and the immersing-drying method were used to immobilize the SPA and anti-E.coli O157:H7 antibody, respectively. The results demonstrated that the immersing-drying method with a low concentration in high dose could obtain a better immobilized effect than the dipping-drying one with a high concentration in low dose. A study on the problem of blocking blank and non-specific sites on the electrode was carried out as follows. Different concentration of the closures, the BSA-PBS solution, were added onto the electrode and a solution with a concentration of 5 mg/mL BSA tended to give out the best performance.(3) The antibody immobilization and antigen detection capacities of the proposed AuNPs-SPA adsorption procedure were investigated in parallel with the bare gold attachment, the directly SPA binding procedure, and the gold nanoparticle direct immobilization procedure. The comparative results suggested that the AuNPs-SPA adsorption procedure, which could significantly improve the immobilized amount of SPA as well as keep them active to absorb antibodies, displaying the best ability in the detection of E.coli 0157:H7.(4) The desired immunosensor was used in the detection of E.coli O157:H7 with different concentrations. The results indicated that in 1.5 h, a detection limit of 102 CFU/mL could be obtained with a working range of 102～105 cfu/mL, in which a good linear relationship was established between the received signal and the concentration of target bacteria. The regression equation was y=73.7x-142.56, with a correlation coefficient of 0.9914.(5) The sensitivity was examined by applying a comparison bacteria named as E.coli DH5a. The results demonstrated that the desired immunosensor was very specific to the target bacteria, which indicated a good performance in its accuracy.From the above research, we explored a new strategy to combine the nanoparticles and piezoelectric immunosensor in order to develop a rapid, sensitive and accurate method in foodborne pathogens detection as well as provide reference to relevant research domains and disciplines.