Highly sensitive immunoassay based on a monoclonal antibody specific for [4-arginine]microcystins

The production and characterization of a monoclonal antibody (clone (MC10E7)) with extraordinary sensitivity and high selectivity for [4-arginine]microcystins is described. The immunogen used for the production of the antibody was synthesized using a novel coupling chemistry to bind microcystin-LR(MC-LR) via dehydroalanine to the carrier protein. With a direct competitive enzyme-linked immunosorbent assay (ELISA) using MC10E7, IC₅₀ values for MC-LR of 0.06 μgl^-1 have been achieved. The detection limit for MC-LR was 6ngl^-1. The provisional guideline value proposed by the World Health Organization (WHO) is 1 μgl^-1 for drinking water. All [4-arginine]microcystins show similar IC₅₀ values and detection limits, whereas other MCs such as MC-LA, are not recognized. The affinity constant for MC10E7 was determined to be at least 7×10¹⁰lmol^-1. The antibody was tested for its robustness against interference of humic acids, pH, salt content, surfactants or organic solvents and was found to be very stable. MC-LR spiked water samples in the concentration range between 0.01 and 0.1 μg1^-1 were measured and a mean recovery of 99.9 ± 16.4% was found. The antibody is well suited for sensitive analysis for MCs in drinking as well as surface water.