Porous PU/PEDOT:PSS electrodes for probing bioelectricity in Oscillatoria sp. Cohorts

Increasing frequency of poor water quality events associated with cyanobacteria strains capable of producing taste and odour (T&O) metabolites and toxins is a global concern for human health and the drinking water industry. This is mostly due to the inability of timely detecting and predicting cyanobacteria productivity associated with water quality risks. Here, we develop and characterize an ultra-sensitive electrophysiology system based on porous polyurethane (PU) foams coated with poly (3, 4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT: PSS) exploiting large-area electrodes of 199 cm², which maximizes the double-layer capacitance and concomitant detection sensitivity. The measured signal of the cyanobacteria model taxa Oscillatoria sp. results from the sum of all individual cell contributions and scales with electrode area, hence indicating correlation with productivity and biomass. Stochastic activity across the cohort is monitored as uncorrelated noise. Yet, when Oscillatoria sp. operate cooperatively, the signal appears as intercellular Ca²⁺ waves which are benchmarked with a conventional fluorescent probe and suppressed with the specific ion channel inhibitor gadolinium chloride. We suggest the existence of a paracrine signaling mechanism with Ca²⁺ acting as the chemical messenger across large cohorts that may prove to be linked with T&O metabolite 2-Methylisoborneol (2-MIB) production. The technology proposed here would enable in-situ real time monitoring of benthic cyanobacteria productivity and hence proxy data for their metabolite production. This paves the way for identifying sources of cyanobacteria metabolites including 2-MIB, geosmin and cyanotoxins, and hence identify intervention solutions and treatment optimization for removal of these detrimental metabolites.