ReviewIn vitro bioassays for detecting dioxin-like activity - Application potentials and limits of detection, a review

- Bioassays with LODs of up to 0.1 pM 2,3,7,8-TCDD may compete with GC-MS.
- Assay applications are diverse (sediment, soil, water, tissue, food, feedstuff).
- Recombinant cell lines achieve lower LODs than there wild type counterparts.
- A bioassay LOD decides on its application (i.e. serum samples need low LODs).
- In vitro studies should list ECx, linear working range and the LOD of an assay.

Use of in vitro assays as screening tool to characterize contamination of a variety of environmental matrices has become an increasingly popular and powerful toolbox in the field of environmental toxicology.While bioassays cannot entirely substitute analytical methods such as gas chromatography-mass spectrometry (GC-MS), the increasing improvement of cell lines and standardization of bioassay procedures enhance their utility as bioanalytical pre-screening tests prior to more targeted chemical analytical investigations. Dioxin-receptor-based assays provide a holistic characterization of exposure to dioxin-like compounds (DLCs) by integrating their overall toxic potential, including potentials of unknown DLCs not detectable via e.g. GC-MS. Hence, they provide important additional information with respect to environmental risk assessment of DLCs.This review summarizes different in vitro bioassay applications for detection of DLCs and considers the comparability of bioassay and chemical analytically derived toxicity equivalents (TEQs) of different approaches and various matrices. These range from complex samples such as sediments through single reference to compound mixtures. A summary of bioassay derived detection limits (LODs) showed a number of current bioassays to be equally sensitive as chemical methodologies, but moreover revealed that most of the bioanalytical studies conducted to date did not report their LODs, which represents a limitation with regard to low potency samples.