Novel developments in rapid mycotoxin detection

Abstract

Rapid antibody-based mycotoxin screening techniques are designed to be used outside a laboratory environment, at the place of sampling. Results are expected immediately, so that commodities can be further processed without delay. Because they are used for mycotoxin analysis, very low levels (ppb and ppt range) should be detected. A further requirement is that the obtained results are accurate with a false negative rate of <5% at the level of interest.

At first, plastic microtiter plates were used as solid phase materials for immobilizing antibodies (enzyme-linked immunosorbent assays). However, to increase speed and user-friendliness, plastics were replaced by microporous membranes. As an example a flow-through enzyme immunoassay for the detection of fumonisins in cornflakes with a cut-off value of 275 μg/kg is described. No false negative results were observed and the false positive rate was 18%. However, enzyme labels, used to enable visual evaluation of results, did not seem to be completely satisfactory in terms of stability and repeatability of the generated signal. Therefore microparticle labels such as colloidal gold particles are used more and more,e.g. in a lateral flow dipstick immunoassay. When applied to the detection of aflatoxin B₁ in pig feed a cut-off value of 5 μg/kg could be reached with no false negative results and a false positive rate of only 10%. Sample pretreatment for screening techniques should be rapid and simple. Preferably a simple solvent extraction is used, followed by a filtration and dilution step. However, for strongly coloured or complex food matrices, this did not seem to work. The combination of clean-up and detection in one single test device is a new approach. When using this clean-up tandem assay column for the detection of ochratoxin A in roasted coffee, a cut-off value of 6 μg/kg was reached. No false positive results were obtained, however, the false negative rate was 8%.