Quantum dot based rapid tests for zearalenone detection
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Three different kinds of immunosorbent assays with luminescence detection were developed for the determination of zearalenone (ZEN), a secondary toxic metabolite of Fusarium fungi. CdSe/ZnS core/shell quantum dots (QDs) were used as a label in quantitative micro-well plate immunoassays (fluorescent-labeled immunosorbent assay, FLISA) and in qualitative column test methods. As carriers for QD-based column tests, sepharose gel (for covalent binding of antibody) and polyethylene frits (for physical absorption of antibody) were used and compared. The application of QDs as a label resulted in a fourfold decrease in the IC50 value with FLISA (0.1 ng mL−1) with a detection limit of 0.03 ng mL−1 when compared with the traditional immunosorbent assay which makes use of horseradish peroxidase as the enzyme label. The cutoff levels for both qualitative column test methods were selected based on the maximum level for ZEN in unprocessed cereals established by the European Commission (100 μg kg−1) as 5 ng mL−1 taking into account extraction and dilution. The different developed immumoassays were tested for ZEN determination in raw wheat samples. As a confirmatory method, liquid chromatography coupled to tandem mass spectrometry was used. The obtained results allow using FLISA and both qualitative column test methods for the analysis of analytes with very low established maximum limits, even in very complicated food matrices, owing to the high dilution of the sample extract.
KeywordsQuantum dots Immunoassay On-site method Enzyme-linked immunoassay Fluorescent-labeled immunoassay Zearalenone
This research was supported by The Russian Foundation of Basic Research (RFBR, project 11-03-93963) and the Special Research Fund (BOF), Ghent, University (01W02008). N.V. Beloglazova also benefits from a fellowship granted by the Belgian Federal Science Policy Office in order to promote the S&T cooperation with Central and Eastern Europe. We gratefully acknowledge Prof. Tom Coenye (Ghent University) for making available the use of Envision 2104 Multilabel Plate Reader and MSc. Marthe De Boevre (Ghent University) for chromatographic experiments.
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