A label-free, direct solid-phase fluorimetric analysis of ochratoxin A in agricultural products with monoclonal antibody-immobilized monolith

Abstract

We established a method for directly measuring mycotoxin ochratoxin A (OTA) in foods by solid-phase fluorescence of monolith-immobilized antibodies. The antibody was introduced onto only one side of an 8 mm-diameter, 3 mm-thick monolith via covalently immobilized protein G. 4 μg (2.7 × 10^-11 mol) of antibody was immobilized per one monolith. A maximum of 10 μg (2.4 × 10^-11 mol) OTA adsorbed to the activated side of each monolith. The amount of OTA adsorbed and the fluorescence intensity showed good linearity in the range of 0.5-3 ng OTA. Loading the sample solution onto the non-antibody side on the monolith blocked the hydrophobic fluorescent matrices from reaching the immobilized surface of the antibody. The proposed method was able to detect 1 ng OTA/g in solid samples with complex matrices. Mean recoveries obtained at spiked concentration of 3 ng g^-1 OTA/g were 78-90% with relative standard deviations of <7.9%.