Abstract
A biosensing system, including an immunomagnetic separation (IMS), a flowinjection and a bienzyme electrode, was developed for rapid detection of Escherichia coliO157:H7 in food samples. Samples inoculated with E. coli O157:H7 were mixed simultaneouslywith magnetic beads coated with anti-E. coli antibodies and alkaline phosphatase labeled anti-E.coli (APLAE) antibodies to form beads-E. coli-APLAE conjugates by antibodyantigen reaction.The conjugates were separated by a magnetic field and then incubated with phenyl phosphate toproduce phenol. An amperometric tyrosinasehorseradish peroxidase biosensor in a flowinjection system was used to detect the phenol concentration that is proportional to the cellnumber of E. coli O157:H7. The biosensor was evaluated using samples of chicken carcass washwater, ground beef and fresh-cut broccoli. This biosensor was able to detect as few as 6 101cells/ml of E. coli O157:H7 under optimized conditions (1 mM MgCl2, 0.4 mg/ml APLAE, and 1mM phenylphosphate in 25 mM Tris buffer solution pH 10.0). The total detection time fromseparating target bacteria with immunomagnetic beads to analyzing flow injectionelectrochemical detection was approximately 2 h.
Published Version
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