Generic microcystin immunoassay based on monoclonal antibodies against Adda

A monoclonal antibody (clone AD4G2) was generated against a common part of microcystins and nodularins, the unusual amino acid Adda [(2S,3S,8S,9S)-3-amino-9-methoxy-2,6,8-trimethyl-l0-phenyldeca-4E,6E-dienoic acid]. A direct competitive ELISA based on this antibody was developed and the cross-reactivity pattern was measured. Different toxins showed a very similar response. The assay provides therefore a sum parameter of microcystins, nodularins and peptide fragments containing Adda. The IC₅₀ for microcystin-LR was 0.33 μg L^-1 which leads to a detection limit of 0.07 μg L^-1. This is well below the concentration of 1 μg L^-1 proposed by the World Health Organisation (WHO) as the limit for drinking water. Microcystin-LR spiked water samples in the concentration range between 0.1 and 1 μg L^-1 were measured and a mean recovery of 113 ± 23% was found. The antibody is well suited for the determination of microcystins in drinking as well as surface water.