Article pubs.acs.org/JAFC
Development of a Model Immunoassay Utilizing Monoclonal Antibodies of Different Specificities for Quantitative Determination of Dieldrin and Heptachlors in Their Mixtures Chiwa Kataoka,*,†,§ Masumi Nihei,† Masaomi Nimata,# and Kazuyuki Sawadaishi† †
Carbuncle BioScienTech LLC, 40-26 Tanida, Okukaiinji, Nagaokakyo 617-0853, Japan Laboratory of Advanced Science and Technology for Industry, University of Hyogo, 3-1-2 Kouto, Kamigori, Ako-gun, Hyogo 678-1205, Japan # Morinaga Institute of Biological Science, Inc., Sachiura 2-1-16, Kanazawa-ku, Yokohama 236-0003, Japan §
ABSTRACT: The presence of dieldrin and heptachlor residues in cucurbitaceous crops at concentrations exceeding the limits set by the Japanese Food Sanitation Law constitutes a serious problem. To prevent accumulation of these residues in cucurbitaceous crops, development of high-throughput analysis methods for the detection of contaminants in the soil before cultivation is required. This study aimed to develop a model immunoassay using new monoclonal antibodies (MAbs) to quantitatively determine dieldrin and heptachlor contents in their mixtures. Three distinctive MAbs were obtained from mice immunized with the respective immunogens. MAb DrA-04 showed high reactivity toward dieldrin with ca. 20% cross-reactivity toward heptachlors. MAb DrC-02 displayed a similar reactivity toward dieldrin and heptachlors. The specificity and sensitivity of MAbs DrA-04 and DrC-02 were largely unaffected by the composition ratio of heptachlors in a mixture. Six standard mixtures with different dieldrin and heptachlor contents were prepared. Concentrations of dieldrin and heptachlors in standard mixtures, calculated on the basis of an immunoassay with MAbs DrA-04 and DrC-02, were 88.1−125 and 96.2−115% of the theoretical values, respectively, revealing excellent sensitivity and specificity of this assay. The developed method paves the way for a facile and rapid quantitative determination of chlorinated cyclodiene pesticides in soil. KEYWORDS: dieldrin, heptachlors, mixtures, model immunoassay, monoclonal antibodies
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INTRODUCTION Drins (aldrin, dieldrin, and endrin) and heptachlors are organochlorine pesticides with a heavily chlorinated dicyclopentadiene ring structure (Figure 1). They are persistent
soil is extremely long, and these compounds and their metabolites thus persist in cultivated fields for long periods of time.5−7 Aldrin is readily oxidized to dieldrin,8 and the majority of heptachlor content is metabolized to heptachlor-cis-epoxide (Figure 1) in the soil.9 These pesticides and their metabolites are taken up by cucurbitaceous crops, such as cucumber (uptake of dieldrin)10−12 and squash (uptake of heptachlors).13 Furthermore, cucurbitaceous crop contamination with these residues has been detected at levels exceeding limits set by the Japanese Food Sanitation Law (dieldrin,
