A bienzyme electrochemical biosensor coupled with immunomagnetic separation for rapid detection of Escherichia coli O157:H7 in food samples

摘要

A biosensing system, including an immunomagnetic separation (IMS), a flow injection and a bienzyme electrode, was developed for rapid detection of Escherichia coli Ol57:H7 in food samples. Samples inoculated with E. coli O157:H7 were mixed with 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 antibody-antigen reaction. The conjugates were separated by a magnetic field and then incubated withphenyl phosphate to produce phenol. An amperometric tyrosinase-horseradish peroxidase biosensor in a flow injection system was used to detect the phenol concentration that is proportional to the cell number of E. coli O157:H7. The biosensor was evaluated using samples of chicken carcass wash water, ground beef and fresh-cut broccoli. This biosensor was able to delect as few as 6 X 10~1 cells/ml of heat-killed E. coli O157:H7 under optimized conditions. The total detection time from separating target bacteria with immunomagnetic beads to analyzing flow injection electrochemical detection was approximately 2 h.