Superfund Research Program
Bioassay Developed for Detection of Dioxin-Like Chemicals
Specific halogenated aromatic hydrocarbons (HAHs), including polychlorinated dibenzo-p-dioxins, furans and biphenyls can cause a variety of toxic and biological effects in animals and man. These types of compounds are considered to be widespread environmental contaminants and are commonly present at hazardous waste sites; therefore, human and wildlife exposure to HAHs is inevitable. In response to the need for a rapid and economical method of detecting these compounds in biological samples, scientists at the University of California at Davis have developed a novel recombinant cell bioassay system which detects bioactive/toxic dioxin-like HAHs in human and animal blood samples. The new bioassay is not only rapid, but is also sensitive and inexpensive to carry out. Furthermore, it provides a means for large scale screening of human and animal blood samples for dioxin-like chemicals.
The bioassay system works by responding to bioactive/toxic dioxin-like HAHs with the induction of firefly luciferase. HAH-mediated induction of luciferase in the recombinant cell system is readily quantitated by measurement of the amount of light produced in an enzyme activity assay and is expressed relative to the most potent HAH, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin). An excellent correlation exists between the amount of light produced and the amount of dioxin-like HAHs present in a sample or sample extract. The cell bioassay system has been adapted to allow for the direct detection of dioxin-like chemicals present in very small amounts (25-50 ul) of whole serum. This assay is very sensitive, with a minimal detection limit of about 1-5 ppt (parts per trillion) TCDD. The assay takes approximately five hours to complete, from the time of sample collection to the acquisition of final results, which is very rapid compared to traditional analytical methods.
The development of this bioassay is significant as it is very sensitive and allows for the analysis of a large number of samples in a rapid and inexpensive manner. This new cell-based bioassay has many practical applications which include use in epidemiological studies for assessing human exposure to dioxin-like chemicals, and in ecological toxicology studies for determining wildlife exposures.
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