Magnetized electrochemically active bacteria-based whole-cell biosensors for real-time sensing of water toxicity

Real-time sensing of water toxicity is essential for environmental health monitoring. However, devising an electrochemically active biofilm-based biosensor for water toxicity assaying usually requires cumbersome culture techniques to immobilize electrochemically active bacteria (EAB) on the electrode, which results in poor timeliness of water quality early-warning. Herein, we developed magnetized electrochemically active bacteria (MEAB)-based whole-cell biosensors (WCBs) for real-time sensing of water toxicity. The results showed that artificial MEAB biofilm could be magnetically constructed in one step within 5 s, which greatly simplified the fabrication process of artificial electrochemically active biofilm. By correlating quantifiable bioelectrical signal with MEAB cell activity, the MEAB-based WCBs enabled detection of Hg²⁺, trichloroacetic acid (TCAA), avermectin (AVM), Cr⁶⁺, and chlortetracycline hydrochloride (CTC) in synthetic water samples within 30 min. The estimated detection limit for Hg²⁺, TCAA, AVM, Cr⁶⁺, and CTC reached 50.4 ± 1.6, 54.7 ± 1.5, 62.8 ± 2.0, 66.8 ± 1.6, and 73.3 ± 2.2 μg L⁻¹ with optimal biomass, respectively. As proof-of-concept applications, the MEAB-based WCBs not only achieved accurate detection of 0.1 mg L⁻¹ toxicants in real water samples but also successfully sensed comprehensive toxicity of agricultural wastewater within 30 min. This study provides a new strategy for real-time sensing of water toxicity.