Whole-cell redox biosensor for triclosan detection: Integrating spectrophotometric and electrochemical detection

Organic pollutants like bisphenol, acetaminophen, and triclosan, widely used in healthcare products, pose environmental risks and act as endocrine disruptors. These pollutants can alter the intracellular redox balance, making engineered whole-cell redox biosensors valuable for their detection. This study utilized the SoxRS regulatory system in bacteria, which responds to oxidative stress through NADP⁺/NADPH levels by modulating gene expression of SoxS through the SoxS promoter (pSoxS). A plasmid containing SoxR-pSoxS and the LacZ reporter gene was constructed and introduced into E. coli BL21 (ΔLacZ SoxRS+). The LacZ gene enabled dual detection using O-nitrophenyl-β-galactopyranoside (ONPG) for spectrophotometric detection or p-aminophenyl β-D-galactopyranoside (PAPG) for electrochemical detection. The whole-cell pRUSL12 redox biosensor was activated by redox inducers such as pyocyanin and methyl viologen, measurable via β-galactosidase assays. Among pollutants tested, triclosan specifically repressed SoxR:pSoxS::lacZ activity in the presence of pyocyanin or methyl viologen. Optimization identified pyocyanin as the more effective inducer for triclosan detection, with the biosensor capable of detecting triclosan in the 100-400 µg/L range. These redox-based biosensors offer a powerful tool for monitoring metabolic redox changes and identifying specific organic pollutants in the environment.