The gold standard for endotoxin detection is the LAL assay. However, due to its enzymatic nature and the dependence on harvesting a wild species, an alternative method could prove to be valuable. Scientists in China and the US recently published a live cell-based option.
The test relies on a specific cell line (293/hTLR4A-MD2-CD14) transfected with all pertinent endotoxin receptor elements and a red fluorescent reporter protein (mCherry) under the control of NF-kB. After transfection, the cells that are exposed to endotoxin trigger a signaling cascade that leads to activation of NF-kB, and therefore, production of mCherry protein. Fluorescence is read in a 96-well format.
The report demonstrates specificity to endotoxin, reliance on the TLR-4 pathway, dose-dependant signal which allows the production of a standard curve, correlation with cytokine (TNFa, IL-8) expression and sensitivity to a wide range of endotoxin species.