Development of a monoclonal immunoassay selective for chlorinated cyclodiene insecticides.

Organochlorine pesticides still generate public health concerns because of their unresolved health impact and their persistence in living beings, which is demanding appropriate analytical techniques for their monitoring. In this study, an enzyme-linked immunosorbent assay based on monoclonal antibodies (MAbs) for the detection of an important group of organochlorine pesticides, the cyclodiene group, has been developed. With this aim, several hapten-protein conjugates, characterized by exposure of the common hexachlorinated bicyclic (norbornene) moiety and differing in the linking structure to the carrier protein, were prepared. From mice immunized with these conjugates, several MAbs with the ability to sensitively bind the majority of cyclodienes were obtained. Among them CCD2.2 MAb displaying the broadest recognition to cyclodiene compounds (endosulfan, dieldrin, endrin, chlordane, heptachlor, aldrin, toxaphene: I(50) values in the 6-25 nM range) was selected for the assay. Interestingly, this MAb showed certain stereospecificity toward other polychlorinated cycloalkanes because the gamma-isomer of hexachlorocyclohexane (lindane) was also very well recognized (I(50) value of 22 nM). This immunoassay is potentially a very valuable analytical tool for the rapid and sensitive determination of cyclodiene insecticides and related compounds, which in turn may contribute to the understanding of the biological activities and of the overall environmental impact of these persistent organic pollutants.

Development of chemiluminescent ELISAs to DDT and its metabolites in food and environmental samples.

Two enzyme-linked immunosorbent assays (ELISA) with chemiluminescent (CL) detection for the insecticide DDT and the group of DDT-related compounds have been optimized and characterized. Both conjugate-coated ELISAs are based on monoclonal antibodies (MAbs) of different specificity and homologous protein conjugates. Effects of several physicochemical factors (ionic strength, pH, Tween-20 and Bovine serum albumin (BSA) concentrations) and solvents (methanol, ethanol, acetone and N,N'-dimethylformamide) on the performance of the assays were studied and optimized. For the DDT-selective assay, the sensitivity, estimated as the I(50) value, was 0.6 microg/l, with a linear working range between 0.1 and 2 microg/l and a limit of detection of 0.06 microg/l. For the DDT group-selective assay, the sensitivity was 0.2 microg/l, with a linear working range between 0.07 and 1 microg/l and a limit of detection of 0.04 microg/l. CL-ELISAs were four times more sensitive compared to colorimetric ELISAs. Finally, both immunoassays were applied to the detection of DDT and group of DDT-related compounds in spiked real water, soil and food samples.