Preparation And Application Of Escherichia Coli Biosensor Based On Quartz Crystal Microbalance(QCM)

Pathogens are widely found in food and the environment,they have a serious effect on public health,even when the amount of intake is infinitesimal.The foodborne diseases caused by them is the world's top food safety issues.E.coli is one of the main species of pathogenic bacteria that reside in human and animal digestive tracts,and it causes various types of damage and pathological changes in the gastrointestinal and urinary systems.However,conventional methods require expensive equipment,complicated operation and time-consuming,which delay results and make it difficult to prevent epidemic outbreaks.At present,the market urgently requires methods that samples without pretreatment and will quickly and sensitively identify pathogens in food,pharmaceutical and public health environments.In this study,quartz crystal microbalance(QCM)is regarded as the means of detection,electrophoresis(DEP)is used as an orderly enrichment tool of biomolecules,escherichia coli O157:H7 is the target of detection,we explored the methods of molecular recognition.The contents and results of this subject include the following aspects:1.We designed to immobilize protein A on the QCM immunosensor surface to increase the binding site of the immune response,the QCM immunosensor was characterized by cyclic voltammetry(CV),electrochemical impedance spectroscopy(EIS),static water contact angle(WCA),reflection infrared spectroscopy(PM-IRRAS)and QCM respectively.Escherichia coli O157:H7 was detected by the prepared immunosensor within a working range 3.0×106~3.0×109 CFU/mL and a limit of detection of 7.0 CFU/mL.When the positive electrophoretic was applied during the detection process,the sensitivity of detection was improved significantly,the working range becomed 3.0×103~3.0×109 CFU/mL and the detection limit was reduced to 5.0 CFU/mL.The regenerative effect of the sensor was not ideal.2.Escherichia coli O157:H7 was used as template molecule,pyrrole was taken as functional monomer,polypyrrole molecularly imprinted(MIP)sensor was prepared by electrochemical polymerization,the sensor was characterized by CV,EIS,WCA and scanning electron microscopy(SEM)respectively,then the potential range of polymerization and the number of polymerization turns were optimized.The detection range of Escherichia coli by this sensor was 3.0~3.0×109 CFU/mL,and the detection limit was 1.0 CFU/m L.After application of positive electrophoresis,the response time was shortened to 10 min effectively.The MIP sensor can recognize E.coli specifically.3.We first proposed the use of QCM instrument to monitor the gas production process of lactose fermentation by E.coli,and then for the detection of E.coli.This method was simple and low cost.100~150 min could obviously monitor the characteristic QCM response of the gas production process,the working range was6.0×106~2.0×108 CFU/mL,the response time was greatly shortened compared with the traditional testing method.We explored a variety of methods to improve the detection sensitivity,but the result was not ideal.The results showed that QCM had no obvious characteristic response to acid production process.The QCM frequency response of the acid-producing bacteria and the gas-acid-producing bacteria fermentation process showed that QCM could specifically detect the gas-acidproducing bacteria.