Polydopamine-Coated Photoautotrophic Bacteria For Improved Extracellular Electron Transfer in Living Photovoltaics

Living photovoltaics represent a growing class of microbial electrochemical devices based on whole cell–electrode interactions able to convert solar energy into electricity. The bottleneck in current microbial electrochemical technologies is the limited electron transfer between the microbe and the electrode surface. This study focuses on the development of a polydopamine (PDA) coating on the outer-membrane of the photosynthetic organism <i>Synechocystis</i> sp. PCC6803. This encapsulation provides a conductive shell to enhance electrode adhesion and improve microbial charge extraction. Cell encapsulation was obtained through an oxygenic dopamine (DA) polymerization in slightly alkaline conditions and the effect of two pH levels (7.5 and 8.2) were examined. PDA-coated cells were characterized and optimized using scanning and transmission electron microscopy (SEM and TEM, respectively) as well as confocal microscopy, UV-Vis and Raman spectroscopies. The microbial exoelectrogenicity was assessed through chronoamperometric measurements. PDA-coated microbes showed three-fold enhanced electron transfer with retained viability and photosynthetic activity.