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Natural toxins in seafood and water have been involved in several toxic incidents throughout the world. A seafood toxin, domoic acid was responsible for the amnesic shellfish poisoning that resulted in 3 possible deaths and over 20 neurological problem victims after they consumed some blue mussels harvested from Prince Edward Island in 1987. Very potent liver toxins (e.g. microcystins) and neurotoxins (e.g. anatoxin-a) are associated with cyanobacterial blooms that are often observed in eutrophic water bodies. Some of these toxins can inhibit enzymes at concentrations or doses that are below the detection limit of the current analytical technologies. Understanding possible health risk and assessing the environmental quality with regard to these natural toxins have been limited by a lack of sensitive and reliable analytical methods for determining specific form of toxins at trace level.
The most sensitive assays for natural toxins are enzyme-linked immunosorbent assay (ELISA) and protein phosphatase bioassay. However, because antibodies target unique structural elements, not the whole antigen, antibodies can fail to discriminate structurally similar species by cross-reacting. Therefore, these assays are not very specific for individual chemical forms of a group of toxins. We are developing alternative assays for natural toxins, therapeutic drugs and environmental contaminants by taking advantage of both immunoassay and modern capillary electrophoresis and chromatography. By combining the immunoassay with chromatography/electrophoresis separation, we improve the specificity of the assay. Cross-reactivity of antibodies with several species of similar structure, which is a problem in conventional immunoassays, can be circumvented by using chromatography or capillary electrophoresis in a second level of discrimination. Such tandem chromatography/electrophoresis - immunoassay systems can also increase the selectivity and the sensitivity of assays by removing interfering species and concentrating the analyte of interest.