Stationary photocurrent generation from bacteriorhodopsin-loaded lipo-polymersomes in polyelectrolyte multilayer assembl
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RESEARCH PAPER
Stationary photocurrent generation from bacteriorhodopsin-loaded lipo-polymersomes in polyelectrolyte multilayer assembly on polyethersulfone membrane Agnieszka Mech-Dorosz 1,2 & Niada Bajraktari 3,4 & Claus Hélix-Nielsen 3,4 & Jenny Emnéus 1 & Arto Heiskanen 1 Received: 15 December 2019 / Revised: 12 February 2020 / Accepted: 17 February 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Vesicles constructed of either synthetic polymers alone (polymersomes) or a combination of polymers and lipids (lipopolymersomes) demonstrate excellent long-term stability and ability to integrate membrane proteins. Applications using lipopolymersomes with integrated membrane proteins require suitable supports to maintain protein functionality. Using lipopolymersomes loaded with the light-driven proton pump bacteriorhodopsin (BR), we demonstrate here how the photocurrent is influenced by a chosen support. In our study, we deposited BR-loaded lipo-polymersomes in a cross-linked polyelectrolyte multilayer assembly either directly physisorbed on gold electrode microchips or cross-linked on an intermediary polyethersulfone (PES) membrane covalently grafted using a hydrogel cushion. In both cases, electrochemical impedance spectroscopic characterization demonstrated successful polyelectrolyte assembly with BR-loaded lipo-polymersomes. Light-induced proton pumping by BR-loaded lipo-polymersomes in the different support constructs was characterized by amperometric recording of the generated photocurrent. Application of the hydrogel/PES membrane support together with the polyelectrolyte assembly decreased the transient current response upon light activation of BR, while enhancing the generated stationary current to over 700 nA/cm2. On the other hand, the current response from BR-loaded lipo-polymersomes in a polyelectrolyte assembly without the hydrogel/PES membrane support was primarily a transient peak combined with a low-nanoampere-level stationary photocurrent. Hence, the obtained results demonstrated that by using a hydrogel/PES support it was feasible to monitor continuously light-induced proton flux in biomimetic applications of lipo-polymersomes.
Keywords Lipo-polymersome . Bacteriorhodopsin . Polyethersulfone membrane . Stationary photocurrent . LbL assembly of polyelectrolytes . Amperometric recording
Introduction Published in the topical collection featuring Female Role Models in Analytical Chemistry. * Arto Heiskanen [email protected] 1
Department of Biotechnology and Biomedicine, Technical University of Denmark, Produktionstorvet, Building 423, 2800 Kgs. Lyngby, Denmark
2
Present address: Novo Nordisk A/S, Brennum Park 24 K, 3400 Hillerød, Denmark
3
Department of Environmental Engineering, Technical University of Denmark, Bygningstorvet, Building 115, 2800 Kgs. Lyngby, Denmark
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Aquaporin A/S, Nymøllevej 78, 2800 Kgs. Lyngby, Denmark
Lipid vesicles constitute a suitable environment for membrane spanning proteins. Therefore, they have been widely used for decades as biomimetic subst
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