Soft Polymer for Enhanced Electron Transfer

Photosynthetic bacteria are anoxygenic microorganisms with highly versatile metabolism, as they use sunlight to oxidize a broad variety of organic compounds in addition to heterotrophic and photoautotropic alternative metabolisms. Conductive polymer layers on the surface of several bacterial species have been used to intercept and funnel the electron flow produced by microbial metabolism outside the cells and transfer it to an electronic circuit of a biohybrid device.<br/>Polydopamine (PDA), produced by self-assembly of dopamine, is a very versatile and bioinspired polymer with widespread applications¹ mostly due its ability to adhere and cover surfaces of different chemical composition. The oxidative conditions employed for the formation of this dark insoluble polymer are mild and biocompatible and have inspired scientists to develop novel nanomaterials. Post-functionalization of PDA² also enables fine tuning of properties.<br/>Furthermore, the ability of this monomer to self-assemble and polymerize in the bacterial growth medium was considered one of the requirements of the polymer to be used as coating material beside the tunable conductive properties and the flexible structure.<br/>Biocompatibility of dopamine was tested by <i>in vivo</i> addition in the growth media of the photosynthetic purple non sulphur <i>Rhodobacter (R.) sphaeroides</i>³ in anoxygenic conditions.<br/>We have used PDA conductive coatings as biotic-abiotic interfaces in biohybrid photoelectrochemical devices through the encapsulation of entire bacterial cells or single components – e.g. photosynthetic reaction center (RC) - of <i>R. sphaeroides</i>^4,5<i>,</i> ensuring electronic communication of the biological component with the electrodes’ surfaces in photoelectrochemical cells.<br/><br/><br/><br/>¹Liu, Y.; Ai, K.; Lu, L. Polydopamine and its derivative materials: Synthesis and promising applications in energy, environmental, and biomedical fields. Chem. Rev. 2014, 114, 5057–5115.<br/><br/>²Buscemi, G., Vona, D., Ragni, R., Comparelli, R., Trotta, M., Milano, F., Farinola, G.M., Polydopamine/Ethylenediamine Nanoparticles Embedding a Photosynthetic Bacterial Reaction Center for Efficient Photocurrent Generation. <i>Adv. Sustainable Syst.</i> 2021, 2000303.<br/><br/>³ Labarile, R.; Varsalona, M.; Vona, D.; Stufano, P.; Grattieri, M.; Farinola, G. M.; Trotta, M., A novel route for anoxygenic polymerization of dopamine via purple photosynthetic bacteria metabolism. <i>MRS Advances </i><b>2023</b><br/><br/>⁴Lo Presti, M., Giangregorio, M. M., Ragni, R., Giotta, L., Guascito, M. R., Comparelli, R., Fanizza, E., Tangorra, R. R., Agostiano, A., Losurdo, M., Farinola, G. M., Milano, F., Trotta, M., Photoelectrodes with Polydopamine Thin Films Incorporating a Bacterial Photoenzyme. <i>Adv. Electron. Mater.</i> 2020, 6, 2000140.<br/><br/>⁵Milano, F., Lopresti, M., Vona, D., Buscemi, G., Cantore, M., Farinola, G.M., Trotta M. (2020). Activity of photosynthetic Reaction Centers coated with polydopamine. <i>MRS Advances 5</i> (45), 2299-2307.