Determination of dioxin concentrations in fish and seafood samples using a highly sensitive reporter cell line, DR-EcoScreen cells

There is a strong need for the development of relatively rapid and low-cost bioassays for the determination of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and dioxin-like polychlorinated biphenyls (dl-PCBs) in environmental and food samples. In this study, we applied a reporter gene assay using DR-EcoScreen cells (DR-cell assay), which is highly sensitive to dioxins, to the determination of PCDD/Fs and dl-PCBs in fish and seafood samples. The PCDD/Fs and dl-PCBs were extracted from homogenated samples (10 g) of 30 fish and shellfish, purified by clean-up procedure using a multilayered silica gel column and an alumina column, and applied to DR-cell assay. Interestingly, the bioanalytical equivalent (BEQ) values obtained from the DR-cell assay <0.1 ∼ 5.4 pg BEQ g⁻¹ wet weight (ww)] were closely correlated with the toxicity equivalent (TEQ) values from conventional high-resolution gas chromatography/high-resolution mass spectrometry (HRGC-HRMS) analysis (r² = 0.912), and the slope of regression line was 0.913. Therefore, we multiplied the BEQ values from the DR-cell assay by a conversion coefficient (1.095, the reciprocal of 0.913) to approximate the TEQ values from the HRGC-HRMS analysis. Furthermore, we used this DR-cell assay to perform a prescreening test of PCDD/Fs and dl-PCBs in 16 fish and seafood samples purchased from a supermarket, revealing that a sample from the fatty flesh of a bluefin tuna exceeded 8 pg TEQ g⁻¹ ww (the European Union-tolerance limit). Taken together, these results suggest that the DR-cell assay might be applicable as a rapid and low-cost prescreening method to determine dioxin levels in fish and seafood samples.