Analysis of DDT Isomers with Enzyme-Linked Immunosorbent Assay and Optical Immunosensor Based on Rat Monoclonal Antibodies as Biological Recognition Elements
Abstract:New rat monoclonal antibodies (mAbs) for DDT [1,1,1-trichloro-2,2-bis (4-chlorophenyl) ethane], namely DDT 7C12, DDT 1C1, and DDT 1B2, were developed, characterized, and applied in ELISA both in coating antigen and in enzyme-tracer format. The latter used horseradish peroxidase (HRP) or glucose oxidase as enzymes. The lowest concentration of p,p-DDT was determined with mAb DDT 7C12 and DDT-hapten HRP, with a test midpoint (IC50) of 0.5 0.2 g/L (n = 10) in 40 mM PBS (phosphate-buffered saline). The mouse anti-rat immunoglobulin lambda-light chain mAb LA1B12 was used as capture mAb. The best IC50 for o,p-DDT in 40 mM PBS was 1.0 0.3 g/L (n = 12) and was obtained with mAb DDT 1C1 and DDT-hapten HRP, whereas mAb DDT 1B2 was very selective for p,p-DDT with an IC50 of 4.2 1.6 g/L (in 40 mM PBS, n = 9). An optical immunosensor was optimized and applied for the analysis of DDT (or DDT equivalents). This immunosensor consists of a bench-top optical readout device and disposable sensor chips, which include the fluidic system. Evanescent field excitation and emission of the fluorophore Oyster-645 was used. An IC50 for p,p-DDT [in 5 (v/v) isopropanol in 40 mM PBS] of 4 g/L was obtained using DDT 7C12-Oyster-645. ELISA and immunosensor were used for the analysis of p,p-DDT in unspiked and spiked surface water samples. Within the working ranges of these immunotechniques, recoveries ranged from 80 to 120.
Document Type: Research Article
Affiliations: 1: Institute of Ecological Chemistry, Helmholtz Center MunichGerman Research Center for Environmental Health, Ingolstdter Landstrae 1, 85764 Neuherberg, Germany. 2: Candor Bioscience GmbH, Eggenwatt 12, 88138 Weiensberg, Germany. 3: Institute of Molecular Immunology, Helmholtz Center MunichGerman Research Center for Environmental Health, Marchioninistrae 25, 81377 Munich, Germany.
Publication date: January 1, 2010
- The Journal of AOAC INTERNATIONAL publishes refereed papers and reviews in the fields of chemical, biological and toxicological analytical chemistry for the purpose of showcasing the most precise, accurate and sensitive methods for analysis of foods, food additives, supplements and contaminants, cosmetics, drugs, toxins, hazardous substances, pesticides, feeds, fertilizers and the environment available at that point in time. The scope of the Journal includes unpublished original research describing new analytical methods, techniques and applications; improved approaches to sampling, both in the field and the laboratory; better methods of preparing samples for analysis; collaborative studies substantiating the performance of a given method; statistical techniques for evaluating data. The Journal will also publish other articles of general interest to its audience, e.g., technical communications; cautionary notes; comments on techniques, apparatus, and reagents.
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