Enzyme-linked immunosorbent assay for microcystins in blue-green algal blooms

• Published in: Journal of the Association of Official Analytical Chemists Vol. 73; no. 3; p. 451
• Main Authors: Chu, F S, Huang, X, Wei, R D
• Format: Journal Article
• Language: English
• Published: United States 01.05.1990
• Subjects: Chromatography, Liquid; Cyanobacteria - analysis; cyanophyta; elisa; Enzyme-Linked Immunosorbent Assay; Immunoenzyme Techniques; Indicators and Reagents; Microcystins; Peptides, Cyclic - analysis; test elisa; toxinas; toxine; toxins; Toxins, Biological - analysis; Water - analysis
• ISSN: 0004-5756
• DOI: 10.1093/jaoac/73.3.451

A direct competitive enzyme-linked immunosorbent assay (ELISA) for the freshwater blue-green algal toxin microcystin (MCYST) in algae and water was developed. The assay involves coating anti-MCYST-variant leucine-arginine (LR) antibody to the ELISA plate and the use of MCYST-LR-peroxidase as the enzyme marker. The linear portion of the standard curve for MCYST in phosphate buffer containing saline (PBS) was 0.5-10.0 ng/mL (25-500 pg/assay). The minimum detection level for MCYST-LR was 0.20 ng/mL (10 pg/assay). Contaminated water could be directly used in the ELISA. The overall analytical recoveries for MCYST-LR added to water at levels of 1-20 ng/mL was 83.4%. For analysis of cellular MCYST, the toxin was first extracted from the algae with 0.1M ammonium bicarbonate, diluted with PBS to less than 0.5 mg dried algae/mL (less than 5.0 mg wet weight/mL) and directly used in the ELISA. C-18 reverse-phase Sep-Pak cartridges effectively adsorbed MCYST from the toxin-containing solutions. The toxin could be recovered from the cartridge by eluting with 60% methanol. Using this approach, an algae extract that was relatively free of MCYST was prepared and was used in a recovery study. The overall analytical recovery of MCYST added to the algae extract in the range of 0.25-20 ppm was 83% with a coefficient of variation of 11.9%. The detection limit for MCYST in dried algae was about 0.25-0.5 microgram/g (0.25-0.5 ppm) lyophilized algae sample. This method was applied for the analysis of several naturally occurring algal blooms. Limited samples were also analyzed for MYCST by liquid chromatography.