Translating Extracellular Electron Transfer Activities with Organic Electrochemical Transistors.

Extracellular electron transfer (EET) is a process through which certain microorganisms can transfer electrons across their cell membranes to external electron acceptors, linking cellular metabolism to their environment. While Geobacter and Shewanella have been the primary models for EET research, emerging studies reveal that EET-active species are also associated with fermentation and the human gut microbiome. Leveraging the ability of EET to bridge biological and electronic systems, we present a protocol for using organic electrochemical transistors (OECTs) to translate microbial EET activity into easily detectable electrical signals. This system enables the use of cellular responses to external stimuli for biosensing and biocomputing applications. Specifically, we demonstrated the de-doping of the p-type poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) channel in the OECT is driven by cellular EET from Shewanella oneidensis. By transcriptionally controlling EET flux by genetic circuits, we establish the biosensing capability of this hybrid OECT system to detect chemical stimuli, such as inducer molecules. Furthermore, we introduce plasmid-based Boolean logic gates within the cells, allowing them to process environmental signals and drive current changes in the OECTs, further demonstrating the biocomputing potential of these devices. This method provides a novel interface between biological systems and electronics, enabling future high-throughput screening, biosensing, and biocomputing applications.