A Bacterial Photosynthetic Enzymatic Unit Modulating Organic Transistors with Light

Abstract

The photochemical core of every photosynthetic apparatus is the reaction center, a transmembrane enzyme that converts photons into charge-separated states across the biological membrane with an almost unitary quantum yield. We present a light-driven organic transistor architecture, which converts light into electrical current by exploiting the efficiency of this biological machinery. Proper surface tailoring enables the integration of the bacterial reaction center as photoactive element in organic transistors, allowing the transduction of its photogenerated voltage into photomodulation of the output current up to two orders of magnitude. The device architecture, termed Light-driven Electrolyte-Gated Organic Transistor (LEGOT), is the prototype of a new generation of low-power hybrid bio-optoelectronic organic devices. Main text Evolution has engineered multi-protein complexes to efficiently convert solar radiation into chemical energy, [1] sustaining the energy needs of life on planet Earth via the photosynthetic process. These photoenzymes catalyze the uphill conversion of oxidized molecules to their reduced forms, using light as energy source. Photosynthetic organisms, such as plants, algae, and some bacteria are the sole kind of organisms on the planet able to harvest and store energy. [2] The photosynthetic anoxygenic bacteria possess a photosynthetic apparatus based on a single functional unit, the reaction center (RC), which converts photons into charge-separated states across the membrane with unmatched quantum yield. Rhodobacter (R.) sphaeroides is a purple non-sulphur bacterium, whose RC is a three-subunit transmembrane protein sitting within the photosynthetic membrane. [3] Light impinges a cascade of electron transfer reactions that forms the hole-electron couple with a unitary quantum yield. [4] In absence of exogenous electron donors and acceptors, this state does not evolve further and has a lifetime ranging from hundred milliseconds up to three seconds. [5] See Figure S1 in the Supporting Information.

Diurnal in vivo xylem sap glucose and sucrose monitoring using implantable organic electrochemical transistor sensors

“…Organic electronic devices can be advantageous when applied in the biological milieu since organic electronic materials support sufficient electronic and ionic transport ( Paulsen et al, 2020 ), in a highly coupled manner, and thus enable efficient signal transduction. While the majority of efforts lie within the animal kingdom, applying bioelectronics to other biological organisms has emerged with successful demonstrations of sensing and actuation in bacteria ( He et al., 2012 ; Pitsalidis et al, 2018 ; Zajdel et al., 2018 ; Demuru et al., 2019 ; Di Lauro et al, 2020 ) and plants ( Stavrinidou et al., 2015 , 2017 ; Coppedè et al., 2017 ; Poxson et al., 2017 ; Bernacka-Wojcik et al, 2019 ; Janni et al, 2019 ; Kim et al., 2019 ; Vurro et al, 2019 ; Diacci et al, 2020 ). Recently, we presented an implantable organic electronic ion pump for in vivo delivery of abscisic acid, one of the main hormones involved in plant stress responses ( Bernacka-Wojcik et al, 2019 ), and subsequently the electronic control of physiology in intact plants.…”

Photoelectrodes with Polydopamine Thin Films Incorporating a Bacterial Photoenzyme

“…Various approaches have been recently reviewed [1,25] and include: 1) layer-by-layer electrostatic adsorption of negatively charged RC onto polycationic modified electrodes; [26] 2) entrapment by physisorption of the protein in nanoporous materials [27,28] and sol-gel media [26] or directly onto the electrode via laser printing [29] or Langmuir-Blodgett techniques; [30,31] 3) covalent binding the RC to the electrode surface by suitable protein linkers or polyhistidine (polyHis) tag at the C-terminal of M subunit of genetically engineered RC; [32] 4) casting a layer of oxidized cyt onto an indium tin oxide (ITO) Gate, prior to RC deposition, to induce an orientation of the photoenzyme that enabled the construction of a novel Light-driven electrolytegated organic transistor. [33] An alternative attaching strategy based on the adhesive properties of polydopamine (PDA) uses a straightforward one-pot molecule encapsulation to produce firmly anchored films on the surface of a dipped electrode in aqueous aerated buffered solution. Dopamine (3,4-dihydroxyphenethylamine, DA) easily polymerizes in presence of oxidant in alkaline aqueous solutions, [34][35][36][37][38][39] forming a robust melanin-like underwater adhesive polymer, [40] the PDA, composed of 5,6-dihydroxy-indole repeating units and its derivatives.…”

Activity of photosynthetic Reaction Centers coated with polydopamine

“…In isolated proteins, instead, light absorption promotes the formation of an electron−hole couple with a conversion yield close to unity, making the RC a biological semiconductor [13]. Given the intense research of such kind of proteins in material science for energy conversion [1,14], synthetic biology [15], biosensing [16][17], and photocatalysis [18], it results interesting to study the behaviour of RCs once entrapped within the suspended PDA nanoaggregates. The RC photoactivity was studied as a function of the starting enzyme/dopamine starting ratio verifying its entrapment without loss of functionality.…”