Charge Capacitive Signatures at the Interface of E. coli/MOF Biohybrids to Create a Live Cell Biocapacitor.

The chemistry of the extracellular electron transfer (EET) process in microorganisms can be understood by interfacing them with abiotic materials that act as external redox mediators. These mediators capture and transfer extracellular electrons through redox reactions, bridging the microorganism and the electrode surface. Understanding this charge transfer process is essential for designing biocapacitors capable of modulating and storing charge signatures as capacitance at the electrode interface. Herein, a novel biointerfacial strategy is presented to investigate directional charge injection from a non-exoelectrogenic living microbe to an electrode surface using the porous metal-organic framework (MOF), MIL-88B. The biohybrid, formed by interfacing Escherichia coli (E. coli) with MIL-88B, demonstrates symbiotic interactions between the biotic and abiotic components, facilitating EET from E. coli to the electrode via the MOF. Acting as a redox mediator, the MOF catalyzes E. coli's exoelectrogenic activity, generating distinct charge capacitive signatures at the E. coli-MOF interface. This system integrates the capacitive signatures resulting from the EET process with the MOF's intrinsic pseudocapacitive properties and surface-controlled capacitive effects, functioning as a highly efficient biocapacitor. Furthermore, this approach of converting the biochemical energy of a non-exoelectrogenic microorganism into capacitive signatures opens a new pathway for translating biological signals into functional outputs, paving the way for autonomous biosensing platforms.