A chemiluminescence fiber-optic biosensor coupled with immunomagnetic separation for rapid detection of E-coli O15:H7

A biosensor, consisting of a chemiluminescence reaction cell, a fiber-optic light guide, and a luminometer linked to a PC, was developed in conjunction with immunomagnetic separation for rapid detection of E. coli O157:H7. The sample containing E. coli O157-H7 was first incubated with anti-E. coli O157-H7 coated magnetic beads and horseradish peroxidase (HRP) labeled anti-E. coli O15TH7 antibodies to form antibody-coated bead - bacteria - HRP-labeled antibody, sandwich complexes. Then, a magnetic field was applied to separate the sandwich complexes from the sample, and the HRP in the complexes catalyzed the reaction of luminol and H2O2 in the reaction cell. The cell number of E. coli O157:H7 was determined by collecting the HRP-catalyzed chemiluminescence signal from the bead surface though a fiber-optic light guide and measuring the signal with a luminometer Key, parameters for the biosensor such as magnetic bead volume, HRP-labeled antibody, concentration, incubation time, and blocking agent, were determined for optimum operation conditions. The chemiluminescence biosensor was selective to E. coli O157:H7 in the presence of other bacteria in the sample, including Salmonella typhimurium, Campylobacter jejuni, and Listeria monocytogenes. The detection limit of the biosensor was 1.8 x 10(2) CFU/mL, and the chemiluminescence signal ranged from 3.8 to 241.0 mV corresponding to E. coli O157-H7 cells from 1.8 X 10(2) to 4.5 x 10(5) CFU/mL A regression model with R-2 = 0.958 was established for a calibration curve over the detection range. The biosensing procedure was simple and rapid, and could be completed within 1.5 h.