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Fluorescence polarization immunoassay (FPIA) is a technique which has been known for a number of years, but despite its many advantages, its has not seen clinical utility. The main reason for this is the lack of simple, rapid, high performance instrumentation suitable for use in a clinical laboratory. This problem has been addressed in this laboratory and an instrument has been developed which meets these needs. The solutions of the two other problems associated with the technique (i.e. non-specific binding of tracer to serum proteins and the intrinsic fluorescence of serum) have also been accomplished. Assays for a variety of therapeutic drugs including gentamicin, theophylline, phenytoin, and phenobarbital have been developed and shown to correlate well with a number of reference method. The assays have been totally automated with a concomitant increase in speed and ease of use and a significant improvement in performance over the manual system.

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Aflatoxins produced by Aspergillus flavus are commonly found in human and animal foods including grains, cereals, peanut products, sorghum, and soy seeds. Exposure to aflatoxins has been associated with carcinogenicity. This paper reports a simple, portable, and rapid fluorescence polarization (FP) assay for aflatoxin determination in grains. This immunoassay is field portable, homogeneous, and without any washing and cleaning steps. The assay is based upon the competition between free aflatoxin and an aflatoxin-fluorescein tracer for an aflatoxin-specific monoclonal antibody in solution. A series of naturally contaminated corn, sorghum, peanut butter, and peanut paste samples were analyzed by FP and compared with HPLC results. Similarly, spiked popcorn samples were analyzed by FP. FP results of naturally contaminated samples correlated well with HPLC (r (2) = 0.97). FP analysis of spiked popcorn samples (with a mixture of B(1)/B(2)/G(1)/G(2), 7/1/3/1, w/w) gave a good correlation with spiked values (r (2) = 0.99). However, FP consistently underestimated the aflatoxin contents. This was perhaps due to low cross-reactivity of the antibody used toward B(2), G(1), and G(2) aflatoxins. These results combined with the portability and simplicity of the assay suggest that the assay can be used for screening total aflatoxin in grains.

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