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

Abstract

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.