Bio-Based Redox Capacitor to Intercede in Microbe-Electrode Electron Flow

The observation that microbes can exchange electrons with electrodes is motivating studies on the conversion of chemical energy into electricity and on the use of electrical energy to drive biosynthesis or bioremediation. Here we present a bio-based redox capacitor, fabricated by the electrically-driven deposition of a thin chitosan film on an electrode and its subsequent functionalization with the redox-active small molecule catechol. This capacitor film is able to intercede in the above-mentioned electron exchanges by collecting electrons from a microbial community and discharging these electrons in predictable ways.

The redox-active but non-conducting bio-based capacitor can undergo specific redox-cycling with several mediators, which enable microbially-facilitated charging and electrochemical charging and discharging.  These phenomena can be harnessed for information processing – the capacitor, along with the two mediators pyocyanin and acetosyringone, allows large amplitude cyclic potential inputs to generate steady current outputs that are amplified, partially-rectified and gated. Here we show how these features enable the sensing of redox-based biological activities and environmental conditions.  Potentially, these capabilities could provide a simple means to sense redox information of complex samples in the clinic or at remote locations. Furthermore, this redox capacitor may provide broader opportunities for connecting biology with electronics.