Magnetic Beads-based Biosensor For Escherichia Coli O157:H7 Detection

Escherichia coli O157:H7 is a kind of shiga-producing Escherichia coli that has become one of the most dangerous food born pathogens. Aiming at the important aspect of pathogenic bacterial detection, this thesis mainly focuses on development of rapid and sensitive detection method for Escherichia coli O157:H7.Laccase-based chemiluminescence immunoassay for Escherichia coli 157:H7 detectionIn this experiment, we have used magnetic beads as a carrier and a simple, low-cost chemiluminescent immunosensor. First, rabbit anti-E.coli O157:H7 polyclonal antibody was immobilized onto magnetic beads. Second, E.coli O157:H7 is then added to induce primary immunorecognition. Biotinylation of monoclonal anti-E. coli O157:H7 antibody initiate the second immunorecognition event. Avidin-glucose oxidase conjugate is localized to magnetic beads via avidin-biotin interaction. Glucose oxidase serves as the biocatalytic label in this chemiluminescent sensor. In this system, the Glucose oxidase mediates the oxidation of glucose in the presence of O2,and yields gluconic acid and H2O2. Then the in-sute produced H2O2 reacts with luminol to generate chemiluminescent signals that serve as the quantitative readout of this sensor. Under optimal conditions, the calibration plot obtained for different concentration of E.coli O157:H7 was approximately linear within the dilution range 4.3×10 CFU mL(-1)-1.7×105 CFU mL-1 CFU mL(-1). The limit of detection (LOD) for the assay was 2.7×103 CFU mL-1.