Broad Cross-Reactivity of a Microcystin ELISA Confirmed Using 19 Quantitative Reference Materials

Microcystins (MCs) are toxins produced by cyanobacteria and are found worldwide. Exposure may be acute or chronic through contaminated drinking water, food (such as vegetables), dietary supplements, and recreational activities. Acute exposure can cause severe liver damage due to the hepatotoxicity of MCs. More than 300 variants of MCs have been reported, making analysis complex, especially since standards are available for only a few MCs. Therefore, a rapid, cost-effective method capable of detecting all MCs in one analysis is essential to protecting public health and livestock. An antibody was raised to a mixture of five MCs creating ELISA_5b, recognizing as many MC variants as possible in a single analysis and with as equal cross-reactivity as possible, avoiding preferential recognition of any specific MC. The updated ELISA_9b was obtained after additional immunization rounds and the cross-reactivities of the two ELISAs were compared using reference materials. Although good cross-reactivity was observed for both ELISAs, ELISA_9b demonstrated better cross-reactivity toward the 19 available reference materials of MCs and nodularin-R. Results obtained with ELISA_9b for water and crayfish stomach samples showed excellent correlation with those obtained with ELISA_5b and LC-HRMS. The limit of quantitation of ELISA_9b for total MCs in drinking water was 0.06 μg/L─well below the WHO's guideline of 1 μg/L for long-term exposure. This ELISA provides a promising tool for the rapid and sensitive quantification of total MCs, including metabolites and conjugates, over a diverse range of sample types.