Towards a novel bioelectrocatalytic platform based on "wiring" of pyrroloquinoline quinone-dependent glucose dehydrogenase with an electrospun conductive polymeric fiber architecture

Electrospinning is known as a fabrication technique for electrode architectures that serve as immobilization matrices for biomolecules. The current work demonstrates a novel approach to construct a conductive polymeric platform, capable not only of immobilization, but also of electrical connection of the biomolecule with the electrode. It is produced upon electrospinning from mixtures of three different highly conductive sulfonated polyanilines and polyacrylonitrile on ITO electrodes. The resulting fiber mats are with a well-retained conductivity. After coupling the enzyme pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) to polymeric structures and addition of the substrate glucose an efficient bioelectrocatalysis is demonstrated. Depending on the choice of the sulfonated polyanilline mediatorless bioelectrocatalysis starts at low potentials;no large overpotential is needed to drive the reaction. Thus, the electrospun conductive immobilization matrix acts here as a transducing element, representing a promising strategy to use 3D polymeric scaffolds as wiring agents for active enzymes. In addition, the mild and well reproducible fabrication process and the active role of the polymer film in withdrawing electrons from the reduced PQQ-GDH lead to a system with high stability. This could provide access to a larger group of enzymes for bioelectrochemical applications including biosensors and biofuel cells

Elektrogesponnene Polymerfasern als neuartiges Material für die Bioelektrokatalyse des Enzyms Pyrrolochinolinchinon-abhängige Glucosedehydrogenase

Es wurde ein dreidimensionales Polymerfasernetzwerk aufgebaut, charakterisiert und anschließend daran das Enzym Pyrrolochinolinchinon-abhängige Glukosedehydrogenase (PQQ)GDH gebunden. Das Polymerfasernetzwerk wurde durch Elektrospinnen einer Mischung des Polymers Polyacrylnitril und verschiedener leitfähiger Polymere der Polyanilin-Familie auf Indium-Zinn-Oxid-Elektroden aufgebracht. Die so hergestellten Fasermatten erwiesen sich bei mikroskopischen Untersuchungen gleichförmig präpariert und die Faserdurchmesser bewegten sich im Bereich weniger hundert Nanometer. Das Redoxpaar Kaliumhexacyanoferrat (II/III) zeigte an diesen Polymer-Elektrodenstrukturen eine quasi-reversible Elektrochemie. Bei weitergehenden Untersuchungen an den enzymmodifizierten Fasern ((PQQ)GDH) konnten unter Substratzugabe (Glukose) bioelektrokatalytische Ströme nachgewiesen werden. Das Fasernetzwerk fungiert hier nicht nur als Immobilisierungsmatrix, sondern als auch als Teil des Signalwandlers.A three-dimensional polymeric electrode structure was developed, characterized and subsequently coupled with the enzyme pyrroloquinoline quinone-dependent Glucosedehydrogenase (PQQ)GDH. The polymeric fiber network is produced by means of electrospinning from mixtures of polyacrylonitrile (PAN) and three different sulfonated poylanilines on top of ITO electrodes. The mats are uniform in their overall appearance; average diameters of the fibers produced are in the range of a few hundred nanometers. These polymeric structures can be shown to allow electrochemical conversions as verified with the ferri-/ferrocyanide redox couple. In addition, application in bioelectrocatalysis can be demonstrated. For two of three selected blends of PAN with sulfonated polyanillines, a well-defined bioelectrochemical response is obtained upon covalent fixation of PQQ-GDH to the fiber network and subsequent addition of substrate glucose. The electrospun matrix does not only act here as an immobilization support, but at the same time as a transducing element

Investigating volume change and ion transport in conjugated polymers

Volume changes are the foundation for a wide range of phenomena and applications, ranging from the movement of plants to valves and drug delivery devices. Therefore, it does not come as a surprise that controlled volume changes are an interesting topic of research. In this thesis, volume changes in polymers are the object of investigation. Polymers are a class of macromolecules that comprise repetitive units. Owing to the wide variety of such units, polymers can exhibit manifold properties, including but not limited to strong water attraction and electrical conductivity. The former is the defining property in polymer hydrogels while the latter is a core property of conducting polymers. Both the water attracting properties and conductivity are closely linked to transport events on a molecular level. In the case of hydrogels, it is predominantly water uptake, while in the case of conducting polymers it is a complex interplay between charges, ionic charge balancing entities and water. However, in either case the transport events lead to volume changes. Despite the similarities, the properties of the materials differ greatly. On the one hand volume changes in hydrogels are very large but hard to control. On the other hand, volume changes in conducting polymers are much smaller than in hydrogels, but the control is easier due to the electronic addressing.    P(gXTX) polymers combine a conducting polymer backbone with hydrogel sidechains. As described in publication 1, this combination of molecular entities was found to enabled unique properties of an electrically controllable giant volume change and concomitant solid-gel transition. In the second publication, the effect of the side chain lengths on the volume change properties of the polymers were explored. The knowledge acquired from these studies helped us to develop an electroactive filter based on p(gXTX) polymers which enabled electrochemical modulation of flow (publication 3). The aim of the fourth publication was to study the complex electronic-ionic transport processes and volume changes in a model conducting polymer, PEDOT:Tos.  The understanding of fundamental processes and properties of controllable volume changes may pave the way for advances in various applications, including electroactive meshes, actuators and drug delivery devices.  

An Electroactive Filter with Tunable Porosity Based on Glycolated Polythiophene

The porosity of filters is typically fixed; thus, complex purification processes require application of multiple specialized filters. In contrast, smart filters with controllable and tunable properties enable dynamic separation in a single setup. Herein, an electroactive filter with controllable pore size is demonstrated. The electroactive filter is based on a metal mesh coated with a polythiophene polymer with ethylene glycol sidechains (p(g3T2)) that exhibit unprecedented voltage-driven volume changes. By optimizing the polymer coating on the mesh, controllable porosity during electrochemical addressing is achieved. The pores reversibly open and close, with a dynamic range of more than 95%, corresponding to over 30 mu m change of pores widths. Furthermore, the pores widths could be defined by applied potential with a 10 mu m resolution. From among hundreds of pores from different samples, about 90% of the pores could be closed completely, while only less than 1% are inactive. Finally, the electroactive filter is used to control the flow of a dye, highlighting the potential for flow control and smart filtration applications.Funding Agencies|Wallenberg Wood Science Center [KAW 2018.0452]; Swedish Research Council - VetenskapsradetSwedish Research Council [VR-2020-05045]; Knut and Alice Wallenberg FoundationKnut &amp; Alice Wallenberg Foundation; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; KAUSTKing Abdullah University of Science &amp; Technology; EPSRCUK Research &amp; Innovation (UKRI)Engineering &amp; Physical Sciences Research Council (EPSRC) [EP/T026219/1]; European UnionEuropean Commission [952911, 862474, 101007084]</p

Cellulose-Conducting Polymer Aerogels for Efficient Solar Steam Generation

Seawater desalination and wastewater purification technologies are the main strategies against the global fresh water shortage. Among these technologies, solar-driven evaporation is effective in extracting fresh water by efficiently exploiting solar energy. However, building a sustainable and low-cost solar steam generator with high conversion efficiency is still a challenge. Here, pure organic aerogels comprising a cellulose scaffold decorated with an organic conducting polymer absorbing in the infrared are employed to establish a high performance solar steam generator. The low density of the aerogel ensures minimal material requirements, while simultaneously satisfying efficient water transport. To localize the absorbed solar energy and make the system floatable, a porous floating and thermal-insulating foam is placed between the water and the aerogel. Thanks to the high absorbance of the aerogel and the thermal-localization performance of the foam, the system exhibits a high water evaporation rate of 1.61 kg m(-2) h(-1) at 1 kW m(-2) under 1 sun irradiation, which is higher than most reported solar steam generation devices.Funding Agencies|Knut and Alice Wallenberg foundation (WWSC 2.0 project); Swedish Research CouncilSwedish Research Council [2016-03979]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO Mat LiU) [2009 00971]; AForsk [18-313]; Finnish Foundation for Technology Promotion; Knut and Alice Wallenberg foundation (Tail of the Sun project)</p

Water Intake and Ion Exchange in PEDOT:Tos Films upon Cyclic Voltammetry: Experimental and Molecular Dynamics Investigation

Conductive polymer PEDOT:Tos (3,4-ethylenedioxythiophene doped with molecular tosylate) gained considerable attention in various devices for bioelectronic applications, such as organic transistors and sensors. Many of these devices function upon oxidation/reduction processes in contact with aqueous electrolytes. So far, theoretical insight into morphological changes, ion injection, and water intake during these processes was rather limited. In the present work, we combined experiments and molecular dynamics simulations to study the water intake, swelling, and exchange of ions in the PEDOT:Tos film during cyclic voltammetry. We showed that the film underwent significant changes in morphology and mass during the redox processes. We observed both experimentally and in simulations that the film lost its mass during reduction, as tosylate and Na were expelled and gained mass during oxidation mainly due to the uptake of anions, i.e., tosylate and Cl. The results were in line with the UV-VIS-NIR absorption measurements and X-ray photoelectron spectroscopy (XPS) measurements, which revealed that during the redox process a portion of Tos was replaced by Cl- as the counterion for PEDOT. Also, the relative mass change between the most oxidized and reduced states was similar to 10 to 14% according to both experiments and simulations. We detected an overall material loss of the film during voltammetry cycles indicating that a portion of the material leaving the film during reduction did not return to the film during the consecutive oxidation. Our combined experimental/simulation study unraveled the underlying molecular processes in the PEDOT:Tos film upon the redox process, providing the essential understanding needed to improve and assess the performance of bioelectronic devices.Funding Agencies|Swedish Research CouncilSwedish Research CouncilEuropean Commission [2016-05990, 2017-04474]; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Swedish e-Science Research Centre (SeRC)</p

Toughening of a Soft Polar Polythiophene through Copolymerization with Hard Urethane Segments

Polar polythiophenes with oligoethylene glycol side chains are exceedingly soft materials. A low glass transition temperature and low degree of crystallinity prevents their use as a bulk material. The synthesis of a copolymer comprising 1) soft polythiophene blocks with tetraethylene glycol side chains, and 2) hard urethane segments is reported. The molecular design is contrary to that of other semiconductor-insulator copolymers, which typically combine a soft nonconjugated spacer with hard conjugated segments. Copolymerization of polar polythiophenes and urethane segments results in a ductile material that can be used as a free-standing solid. The copolymer displays a storage modulus of 25 MPa at room temperature, elongation at break of 95%, and a reduced degree of swelling due to hydrogen bonding. Both chemical doping and electrochemical oxidation reveal that the introduction of urethane segments does not unduly reduce the hole charge-carrier mobility and ability to take up charge. Further, stable operation is observed when the copolymer is used as the active layer of organic electrochemical transistors.Funding Agencies|Swedish Research CouncilSwedish Research Council [2016-06146, 2018-03824]; Knut and Alice Wallenberg Foundation through a Wallenberg Academy Fellowship; European Research Council (ERC)European Research Council (ERC) [637624]; National Science FoundationNational Science Foundation (NSF) [NSF DMR-1751308]; Northwestern University Office of Undergraduate Research; Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource [NSF ECCS-1542205]; Materials Research Science and Engineering CenterNational Science Foundation (NSF) [NSF DMR-1720139]; State of Illinois; Northwestern University; International Institute for Nanotechnology (IIN); Keck FoundationW.M. Keck Foundation; State of Illinois, through the IIN; Wallenberg Wood Science Center [KAW 2018.0452]</p

Side Chain Redistribution as a Strategy to Boost Organic Electrochemical Transistor Performance and Stability

A series of glycolated polythiophenes for use in organic electrochemical transistors (OECTs) is designed and synthesized, differing in the distribution of their ethylene glycol chains that are tethered to the conjugated backbone. While side chain redistribution does not have a significant impact on the optoelectronic properties of the polymers, this molecular engineering strategy strongly impacts the water uptake achieved in the polymers. By careful optimization of the water uptake in the polymer films, OECTs with unprecedented steady-state performances in terms of [mu C*] and current retentions up to 98% over 700 electrochemical switching cycles are developed.Funding Agencies|KAUSTKing Abdullah University of Science &amp; Technology; King Abdullah University of Science and Technology Office of Sponsored Research (OSR) [OSR-2018-CARF/CCF-3079, OSR-2015-CRG4-2572, OSR-4106 CPF2019]; EC FP7 Project SC2 [610115]; EC H2020 [643791]; EPSRCEngineering &amp; Physical Sciences Research Council (EPSRC) [EP/G037515/1, EP/M005143/1, EP/L016702/1]; Knut and Alice Wallenberg FoundationKnut &amp; Alice Wallenberg Foundation; Wallenberg Wood Science Center [KAW 2018.0452]; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoping University [2009-00971]; TomKat Center for Sustainable Energy at Stanford University</p

Side Chain Redistribution as a Strategy to Boost Organic Electrochemical Transistor Performance and Stability

A series of glycolated polythiophenes for use in organic electrochemical transistors (OECTs) is designed and synthesized, differing in the distribution of their ethylene glycol chains that are tethered to the conjugated backbone. While side chain redistribution does not have a significant impact on the optoelectronic properties of the polymers, this molecular engineering strategy strongly impacts the water uptake achieved in the polymers. By careful optimization of the water uptake in the polymer films, OECTs with unprecedented steady-state performances in terms of [mu C*] and current retentions up to 98% over 700 electrochemical switching cycles are developed.Funding Agencies|KAUSTKing Abdullah University of Science &amp; Technology; King Abdullah University of Science and Technology Office of Sponsored Research (OSR) [OSR-2018-CARF/CCF-3079, OSR-2015-CRG4-2572, OSR-4106 CPF2019]; EC FP7 Project SC2 [610115]; EC H2020 [643791]; EPSRCEngineering &amp; Physical Sciences Research Council (EPSRC) [EP/G037515/1, EP/M005143/1, EP/L016702/1]; Knut and Alice Wallenberg FoundationKnut &amp; Alice Wallenberg Foundation; Wallenberg Wood Science Center [KAW 2018.0452]; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoping University [2009-00971]; TomKat Center for Sustainable Energy at Stanford University</p