Online self-powered Cr(VI) monitoring with autochthonous Pseudomonas and a bio-inspired redox polymer.

The assessment of water quality is critical to implement preventive and emergency interventions aimed to limit/avoid environmental contamination and human exposure to toxic compounds. While established high-resolution techniques allow quantitative and qualitative determination of contaminants, their widespread application is not feasible due to cost, time, and need for trained personnel. In this context, the development of easy-to-implement approaches for preliminary detection of contaminants is of the utmost importance. Herein, a portable self-powered microbial electrochemical sensor enabling online monitoring of Cr(VI) is reported. The biosensor employs a bio-inspired redox mediating system to allow extracellular electron transfer between a bacterial isolate from chromium-contaminated environments and the electrode, providing a clear response to Cr(VI) presence. The biosensor shows good linearity (R2 = 0.983) and a limit of detection of 2.4 mg L-1 Cr(VI), with a sensitivity of 0.31 ± 0.02 μA cm-2 mgCr(VI)-1 L. The presented microbial bioanode architecture enhanced biosensor performance thanks to the improved "electrical wiring" between biological entities and the abiotic electrode surface. This approach could be easily implemented in engineered electrode surfaces, such as paper-based multi-anodes that maximize bacterial colonization, further improving biosensor response. Graphical abstract.