Photosynthetic Microorganisms for Optoelectronics

Photosynthetic microorganisms and their molecular components for light absorption and photoconversion, optimized over billions of years of evolution, represent attractive tools for harvesting and conversion of solar light in sustainable and cost-effective transducers. The new era of biohybrid devices relies on the exploitation of isolated structures from these microorganisms, or the entire living cells, as the active components for photoconversion in optoelectronic devices and photoelectrochemical cells [1].<br/>The bacterial reaction center (RC) extracted from the purple non-sulphur bacterium <i>Rhodobacter (R.) sphaeroides</i> has been initially modified by covalent functionalization with organic molecules specifically designated to act as artificial antennas to increase its light absorption capability [2].<br/>The same RC has been also integrated into photoactive transistors [3], using molecular or polymeric semiconductor thin films deposited onto metal electrodes as interfaces [4]. Among them polydopamine (PDA), a biocompatible polymer produced <i>via </i>self-oxidative polymerization of the dopamine monomer, gave very interesting results for the stabilization of <i>R. sphaeroides </i>RCs. RC has been immobilized both in PDA thin films on the electrode surfaces or in PDA nanoparticles, without altering the enzymatic photoactivity, and producing photocurrents in photoelectrochemical cells [5]. PDA has been modified with diamines, leading to more transparent nanostructures incorporating RC molecules, which outperform RC/PDA structures in light transmission and photoconversion [6].<br/>Finally, we have been investigated different approaches for interfacing intact photosynthetic microorganisms with electrodes, enabling photoconversion of whole living cells of <i>R. sphaeroides </i>and <i>R. capsulatus</i>, using PDA as the interface material either as a coating on the cells’ surface, or as a film entrapping the cells on the electrode surface [7].<br/>Furthermore, eukaryotic diatoms have been also selected for their efficiency in harvesting and converting sunlight into chemical energy and the feasibility of silica shell functionalization. Electrochemical characterizations have been performed to understand the electronic transfer between diatoms and electrodes, using different redox mediators.<br/><br/>[1] F. Milano, A. Punzi, R. Ragni, M. Trotta, G. M. Farinola, <i>Adv. Funct. Mater</i>., <b>29</b>, 1805521, (2019).<br/>[2] F. Milano, R.R. Tangorra, O. Hassan Omar, R. Ragni, A. Operamolla, A. Agostiano, G.M. Farinola, M. Trotta, <i>Angew. Chem.</i> Int. Ed., 51: 11019-11023 (2012)<br/>[3] M. Di Lauro, S. la Gatta, C.A. Bortolotti, V. Beni, V. Parkula, S. Drakopoulou, M. Giordani, M. Berto, F. Milano, T. Cramer, M. Murgia, A. Agostiano, G.M. Farinola, M. Trotta, F. Biscarini “A Bacterial Photosynthetic Enzymatic Unit Modulating Organic Transistors with Light”, Adv. Electronic Mater. <b>6 </b>(1), 1900888 (2020).<br/>[4] E. D. Glowacki, R. R. Tangorra, H. Coskun, D. Farka, A. Operamolla, Y. Kanbur, F. Milano, L. Giotta and N. S. Sariciftci “Bioconjugation of hydrogen-bonded organic semiconductors with functional proteins”, J. Mater. Chem. C, <b>3 </b>(25), 6554-6564 (2015).<br/>[5] M. Lo Presti, M. M. Giangregorio, R. Ragni, L. Giotta, M. R. Guascito, R. Comparelli, E. Fanizza, R. R. Tangorra, A. Agostiano, M. Losurdo, G. M. Farinola, F.Milano, M. Trotta “Photoelectrodes with Polydopamine Thin Films Incorporating a Bacterial Photoenzyme”, Adv. Electron. Mater. 2000140 (2020).<br/>[6] G. Buscemi, D. Vona, R. Ragni, R. Comparelli, M. Trotta, F. Milano, G. M. Farinola “Polydopamine/Ethylenediamine Nanoparticles Embedding a Photosynthetic Bacterial Reaction Center for Efficient Photocurrent Generation”, Adv. Sustain. Syst., doi.org/<b>10.1002/adsu.202000303 </b>(2021).<br/>[7] G. Buscemi, D. Vona, P. Stufano, R. Labarile, P. Cosma, A. Agostiano, M. Trotta, G.M. Farinola, M. Grattieri. Bio-inspired redox-adhesive polydopamine matrix for intact bacteria biohybrid photoanodes. ACS Applied Materials & Interfaces, 2022, 14(23), pp. 26631–26641