A porous PEDOT:PSS-cyanobacteria biohybrid for electrochemical assessment of photosynthetic activity

Cyanobacteria are both an emerging platform in sustainable biotechnology, whilst also potentially harmful to water quality in lakes and reservoirs. In both cases, it is surprising that assessment of productivity and abundance still rely upon invasive and often costly and laborious techniques. In this work we devised a biohybrid platform which continuously monitors photosynthetic activity in cyanobacteria, non-invasively and effortlessly. The biohybrid consists of ensembles of Oscillatoria sp. adherent on porous poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) electrodes, which functions as an efficient interface for transducing photosynthetic electron exchange. Open Circuit Potential (OCP) recordings over time were found proportional to the natural light-dark cycles while chronoamperometry revealed light-driven photocurrents absent in abiotic controls. Moreover, cross-correlation analysis between temperature and OCP revealed a distinct phase shift and latency when Oscillatoria sp. colonized the electrode, as opposite to medium-only controls, ascertaining a strong biological contribution beyond thermal effects. Overall, this work cements PEDOT:PSS electrodes as a scalable, label-free tool for assessing cyanobacteria photosynthetic activity enabling affordable and continuous water quality monitoring.