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Sensors 2006, 6(8), 796-807; doi:10.3390/s6080796
Article

Fiber-Optic Biosensor Employing Alexa-Fluor Conjugated Antibody for Detection of Escherichia coli O157:H7 from Ground Beef in Four Hours

1, 2, 2 and 1,*
1 Molecular Food Microbiology Laboratory, Department of Food Science, Purdue University, 745 Agriculture Mall Dr., West Lafayette, Indiana 47907 2 United States Department of Agriculture, Agricultural Research Service, NAA Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, PA 19038
* Author to whom correspondence should be addressed.
Received: 3 February 2006 / Accepted: 12 April 2006 / Published: 19 August 2006
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Abstract

Fiber optic biosensor has a great potential to meet the need for rapid, sensitive,and real-time microbial detection systems. We developed an antibody-based fiber-opticbiosensor to rapidly detect low levels of Escherichia coli O157:H7 cells in ground beef. Theprinciple of the sensor is a sandwich immunoassay using an antibody which is specific forE. coli O157:H7. A polyclonal antibody was first immobilized on polystyrene fiberwaveguides through a biotin-streptavidin reaction that served as a capture antibody. AnAlexa Fluor 647 dye-labeled antibody to E. coli O157:H7 was used to detect cells andgenerate a specific fluorescent signal, which was acquired by launching a 635 nm laser-lightfrom an Analyte-2000. Fluorescent molecules within several hundred nanometers of thefiber were excited by an evanescent wave, and a portion of the emission light fromfluorescent dye transmitted by the fiber and collected by a photodetector at wavelengths of670 to 710 nm quantitatively. This immunosensor was specific for E. coli O157:H7compared with multiple other foodborne bacteria. In addition, the biosensor was able todetect as low as 103 CFU/ml pure cultured E. coli O157:H7 cells grown in culture broth.Artificially inoculated E. coli O157:H7 at concentration of 1 CFU/ml in ground beef couldbe detected by this method after only 4 hours of enrichment.
Keywords: Escherichia coli O157:H7; fiber-optic biosensor; antibodies; detection; ground beef. Escherichia coli O157:H7; fiber-optic biosensor; antibodies; detection; ground beef.
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Geng, T.; Uknalis, J.; Tu, S.-I.; Bhunia, A.K. Fiber-Optic Biosensor Employing Alexa-Fluor Conjugated Antibody for Detection of Escherichia coli O157:H7 from Ground Beef in Four Hours. Sensors 2006, 6, 796-807.

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