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United States Department of Agriculture

Agricultural Research Service

Title: An Evanescent Wave-Based Fiber Optic Immunosensor for Aflatoxin B1

Author
item Maragos, Chris

Submitted to: Association Official Analytical Chemists Midwest Section Program Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: June 10, 1998
Publication Date: N/A

Technical Abstract: An evanescent wave-based fiber optic immunosensor was developed for the detection of aflatoxins in solution. This assay was based upon the binding of aflatoxin B1 (AFB1) to a monoclonal antibody covalently attached to silica fibers. Binding of the aflatoxin to the antibody detained aflatoxin molecules within the zone of excitation light (evanescent wave, 360 nm) near the surface of the fiber. A portion of the fluorescence emitted from the aflatoxin (427 nm) was coupled back into the sensor and detected using a sensitive fluorometer. In this manner, a noncompetitive immunoassay for aflatoxins was developed, wherein the response of the sensor was directly proportional to the concentration of aflatoxin present. The monoclonal antibody developed showed cross reactivity to aflatoxin B1 (100%), G1 (44%), B2 (37%), G2 (13%), and M1 (6%) in a competitive direct enzyme-linked immunosorbent assay (ELISA) format. The limit of detection of the immunosensor, with toxin in phosphate buffered saline, was 2 ng of AFB1/mL. Fibers were exposed to as many as 20 cycles of aflatoxin followed by buffer with minimal impact upon the magnitude of the fluorescent response, indicating each fiber may be used for many analyses. The freedom from matrix interferences and the speed with which samples can be analyzed suggest the fiber optic immunosensor can be adapted for the rapid and sensitive screening for AFB1 in maize.

Last Modified: 11/27/2014
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