CALUX system

Table 3 Examples of in vitro and in vivo bioassays for which standard operating procedures have been developed (Schipper and Stronkhorst 1999) and studied for their applicability in the licensing system for disposal of dredged sediment (own results) or were evaluated in other studies (e.g. ER-CALUX).

The in vitro bioassay for dioxins with cleaned sediment extracts (DR-CALUX) proved to comply with the QA/QC criteria needed to guarantee the reliability of data in an inter- and intralaboratory study (Besselink et al., 2004). The chemical stability of dioxins makes it possible to apply destructive clean-up procedures which remove all matrix factors. Sample extraction and cleanup for other in vitro bioassays for specific mechanisms of toxicity require further development to make sure that the chemicals of interest are not lost or unwanted chemicals included in the sediment extract to be tested. Table 4 summarizes possible bioassays that could be performed in addition to chemical analyses with the dredged sediment in a licensing system. 

Denison, M.S., Rogers, W.J., Fair, M., Ziccardi, M., Clark, G., Murk, A.J., Brouwer, A. (1996). Application of the CALUX bioassay system for the detection of dioxin-like chemicals (Ah receptor ligands) in whole serum samples and in extracts fiom commercial and consumer products. Organohalogen Compounds 27 280-284. 

An additional screening test for TCDD-like (aryl hydrocarbon receptor, AhR, active) chemicals has been developed (Garrison et al. 1996) and is available commercially (Anonymous 1997). Dubbed the CALUX (for chemically activated luciferase gene expression) system, the assay is based on recombinant cell lines into which researchers have inserted a firefly luciferase gene. When exposed to dioxin-like compounds, the recombinant cells luminesce. The method is sensitive to ppt levels of 2,3,7,8-TCDD equivalents in blood, serum, and milk (Anonymous 1997). Samples testing positive can be subjected to more definitive and specific analytical testing. 

Biosensors differ from bioassays mainly by the fact that in bioassays the transducer is not an integral part of the analytical system and biosensors can extract quantitative analytical information of single compounds in complex mixtures. One example is the determination of concentrations of dioxin-like compounds in the blood and environmental samples using the Calux assay, where within a complex matrix its levels are determined with great accuracy (see, e.g., Murk et al. 1997). Additionally, compounds that are difficult to detect (e.g., surfactants, chlorinated hydrocarbons, sulfophenyl carboxylates, dioxins, pesticide metabolites) can more easily be evaluated using biosensors. 

In 2005, the Ministry of the Environment of Japan evaluated four novel simple bioassays for monitoring dioxin contamination in effluent gas, fly ash, and cinders. In the CALUX assay, recombinant mouse hepatoma cells (HlL6.1c2) with four dioxin-responsive elements upstream of the luciferase gene are treated with extracts from contaminated samples, and the luciferase activity is then measured [2]. Luciferase activity induced in the recombinant human hepatoma cell line lOlL and the recombinant mouse hepatoma cell line HeB5 is utilized in the P450 Human Reporter Gene System (HRGS) and Ah luciferase assays, respectively [3]. 

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