Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/1998
Publication Date: N/A
Citation: N/A Interpretive Summary: Dioxin is a long-lived, toxic chemical that was discovered as a contaminate in many industrial compounds such as weed killers. Dioxin actually refers to a collection of 75 chemicals, all with the same basic structure but differing in the number of chlorine atoms. Only a subset of these are highly toxic. Therefore in order to analyze for dioxin a sophisticated, expensive ($1500-2000/sample) analysis is needed to detect the toxic forms of dioxin. This paper describes efforts at development of a simple, inexpensive assay to detect the most toxic forms of dioxin. This assay is an immunoassay and thus it is based on production of an antibody that specifically binds the dioxin. Recent surveys have detected trace levels of dioxins in some foods. The assay described has the potential to serve as an cost effective screening test. Thus, it would be useful for food producers and others who desire to check ingredients or final products for unwanted trace contaminations.
Technical Abstract: This paper reports the synthesis of haptens and the generation and preliminary evaluation of polyclonal antibodies for the detection of TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) by ELISA (enzyme-linked immunosorbent assay). These novel haptens contain unsaturation between the halogenated dibenzo-p-dioxin ring system and the protein to which it is conjugated, presenting a rigid handle structure. The substitution pattern is identical or similar to TCDD (i.e., 2,3,7,8- or 1,2,3,7,8-). Finally, the haptens lack polar groups for hydrogen bonding. In direct binding assays using the new polyclonal antibodies, there was excellent recognition of hapten-protein conjugates, including recognition of those hapten-conjugates that were not used as immunogens (i.e., assay systems heterologous in hapten structure). These haptens do elicit selective immune responses in rabbits. Their evaluation in an ELISA format demonstrated the usefulness of these haptens for the detection of TCDD. An IC50 of 0.8 ng/well (16 ng/mL) was observed for an unoptimized system. Initial assays were evaluated using 2,3,7-trichloro-8-methyl-dibenzo-p- dioxin as an analytical surrogate that gave a response identical to TCDD in the ELISA.