Residues of human pharmaceuticals, such as nonsteroidal anti-inflammatory drugs (NSAIDs) are increasingly found in effluent wastewater of treatment plants (WWTP) and represent a potential environmental threat. NSAIDs reduce pain and inflammation by inhibiting cyclooxygenases (COX) and thereby the production of prostanoids such as prostaglandins. The amino acid sequence of COX targeted by NSAIDs is evolutionarily highly conserved among vertebrates. Thus, organisms expressing COX may physiologically respond to COX inhibiting NSAIDs. For risk assessment one has to know the extent to which aquatic organisms are exposed to NSAIDs as well as metabolites with the same mode of action.
Therefore, we developed and validated a cell-based mode-of-action (MOA) assay, by which the total NSAID activity in a wastewater can be measured as equivalents of the lead substance diclofenac (DicEQ). The CLARIOstar multi-mode microplate reader reliably detected the ratiometric roGFP probe using its unique LVF monochromator™. Its flexibility to record fluorescence spectra supported development of the NSAID assay.