Comparative study of colloidal gold and quantum dots as labels for multiplex screening tests for multi-mycotoxin detection.

Quantum dots (QDs) and colloidal gold nanoparticles (CG) were evaluated as labels for multiplex lateral flow immunoassay (LFIA) for determination of mycotoxins deoxynivalenol (DON), zearalenone (ZEN) and T2/HT2-toxin (T2/HT2) in cereal matrices. Both developed assays were based on the same immunoreagents (except for the labels), therefore their analytical characteristics could be objectively compared. For both LFIAs antigens (DON-ovalbumin (OVA), ZEN-OVA and T2-OVA) and rabbit anti-mouse immunoglobulin were immobilized on a nitrocellulose membrane as three test lines and one control line, respectively. Depending on the LFIA, monoclonal antibodies (mAb) against DON, ZEN and T2 were conjugated with CdSeS/ZnS QDs or CG. T2 and HT2 were detected by one test line (T2-OVA) with an anti-T2 mAb which showed 110% cross-reactivity with HT2. Both tests were developed in accordance with the legal limits and were developed in such a way that they had the same cut-off limits of 1000 μg kg-1, 80 μg kg-1 and 80 μg kg-1 for DON, ZEN and T2/HT2, respectively in order to allow a correct comparison. Applicability of these assays was demonstrated by analysis of naturally contaminated wheat samples. The results demonstrate that both the LFIAs can be used as rapid, cost-effective and convenient qualitative tool for on-site screening for simultaneous detection of DON, ZEN and HT2/T2 in wheat without special instrumentation. However, the QD-based LFIA consumed less immunoreagents and was more sensitive and economically beneficial. In addition, the results were easier to interpret, resulting in a lower false negative rate (<5%) which was in good agreement with Commission Decision 2002/657/EC regarding the performance of analytical methods intended for screening purposes.