A comprehensive immunoassay for the detection of microcystins in waters based on polyclonal antibodies

Microcystins (MCs) are a group of closely related toxic cyclic heptapeptides produced by common cyanobacteria (blue-green algae), and microcystin–leucine–arginine (MC-LR) is among the most frequent and most toxic microcystin congeners. In this study, a free amino group was introduced to MC-LR at its seventh amino acid residue with 2-mercaptoethylamine, and the product aminoethyl-MC-LR was coupled to bovine serum albumin (BSA) and horseradish peroxidise (HRP) by glutaraldehyde to be complete antigen (MC-LR-BSA) and labelled hapten (MC-LR-HRP), respectively. Polyclonal antibodies against MC-LR were generated by immunization with MC-LR-BSA. A direct competitive enzyme-linked immunosorbent assay (dc-ELISA) was established to detect the MCs in waters, which showed a good cross-reactivity with MC-LR, MC-RR, MC-YR, MC-LF, MC-LW and nodularin, and have a detection limit for MC-LR 0.12 μg L−1, the 50% inhibition concentration (IC50) for MC-LR was 0.63 ± 0.06 μg L−1 and the quantitative detection range was from 0.17 to 2.32 μg L−1, the analysis result of water samples showed good recovery and reliability. So the comprehensive and reliable dc-ELISA will well potentially suit for sensitive analysis for total MCs in drinking as well as resource water samples.