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

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

Mechanistische Untersuchung von protonengekoppeltem Elektronentransfer und den Substitutionsreaktionen biologisch relevanter Systeme

The objective of the present work was to study seven-coordinate FeII and FeIII complexes of acyclic and rigid pentadentate H2dapsox [H2dapsox = 2,6-diacetylpyridine-bis(semioxamazide)] ligands in aqueous and nonaqueous media. Since these complexes were proven to be outstanding catalysts for SOD disproportionation, the clarification of the following aspects was of importance: investigations of pressure effects on the thermodynamics of proton-coupled electron-transfer reactions of different complex species in aqueous solution; establishment of the reaction mechanism over a wide pH range: whether electrons and protons (1H+/1e- or 2H+/1e-) are transferred in one kinetic step (concerted transfer) or separately in a stepwise manner; studies on the host−guest interactions between the FeII/IIIdapsox system and small ions: SOD mimetic as a ditopic receptor in aprotic mediumDa die Eisenkomplexe des azyklischen und starren Liganden H2dapsox [H2dapsox=2,6-diacetylpyridin-bis(semioxamazid)] Superoxid dismutieren können, ist das detaillierte Verständnis des Redoxverhaltens und der Substitutionsreaktionen von fundamentaler Bedeutung. Es war von besonderer Wichtigkeit, folgende Aspekte in der vorliegenden Dissertation zu erläutern: Wie ist der Einfluss von Druck auf die Thermodynamik protonengekoppelter Elektronentransferreaktionen verschiedener Komplexspezies in wässrigen Lösungen? Die Aufklärung des Mechanismus elementarer Reaktionsschritte innerhalb eines großen pH-Bereichs: Werden Protonen und Elektronen als separate Teilchen oder in einem Reaktionsschritt übertragen? Die Wirt−Gast Wechselwirkungen zwischen dem FeII/IIIdapsox System und kleinen Metallionen: Ist das SOD-Mimetikum ein ditopischer Rezeptor? Die Klärung der grundlegenden Prozesse und Wechselwirkungen, in denen die siebenfach koordinierten Komplexe eine Rolle spielen, kann zum Verständnis des SOD Katalyseprozesses beitragen und ein Licht auf die funktionellen Details der effizienten Mimetika werfen. Da die Eisenkomplexe des azyklischen und starren Liganden H2dapsox [H2dapsox=2,6-diacetylpyridin-bis(semioxamazid)] Superoxid dismutieren können, ist das detaillierte Verständnis des Redoxverhaltens und der Substitutionsreaktionen von fundamentaler Bedeutung. Es war von besonderer Wichtigkeit, folgende Aspekte in der vorliegenden Dissertation zu erläutern: Wie ist der Einfluss von Druck auf die Thermodynamik protonengekoppelter Elektronentransferreaktionen verschiedener Komplexspezies in wässrigen Lösungen? Die Aufklärung des Mechanismus elementarer Reaktionsschritte innerhalb eines großen pH-Bereichs: Werden Protonen und Elektronen als separate Teilchen oder in einem Reaktionsschritt übertragen? Die Wirt−Gast Wechselwirkungen zwischen dem FeII/IIIdapsox System und kleinen Metallionen: Ist das SOD-Mimetikum ein ditopischer Rezeptor? Die Klärung der grundlegenden Prozesse und Wechselwirkungen, in denen die siebenfach koordinierten Komplexe eine Rolle spielen, kann zum Verständnis des SOD Katalyseprozesses beitragen und ein Licht auf die funktionellen Details der effizienten Mimetika werfen

Investigation of the mediated electron transfer mechanism of cellobiose dehydrogenase at cytochrome c-modified gold electrodes

The present study reports on the comparison of direct and mediated electron transfer pathways in the interaction of the fungal enzyme cellobiose dehydrogenase (CDH) with the redox protein cytochrome c (cyt c) immobilised at a modified gold electrode surface. Two types of CDHs were chosen for this investigation: a basidiomycete (white rot) CDH from Trametes villosa and a recently discovered ascomycete from the thermophilic fungus Corynascus thermophilus. The choice was based on the pH-dependent interaction of these enzymes with cyt c in solution containing the substrate cellobiose (CB). Both enzymes show rather similar catalytic behaviour at lower pH, dominated by a direct electron exchange with the electrode. With increasing pH, however, also cyt c-mediated electron transfer becomes possible. The pH-dependent behaviour in the presence and in the absence of cyt c is analysed and the potential reaction mechanism for the two enzymes with a different pH-behaviour is discussed. (c) 2011 Published by Elsevier B.V

Investigation of the pH-Dependent Impact of Sulfonated Polyaniline on Bioelectrocatalytic Activity of Xanthine Dehydrogenase

We report on the pH-dependent bioelectrocatalytic activity of the redox enzyme xanthine dehydrogenase (XDH) in the presence of sulfonated polyaniline PMSA1 (poly­(2-methoxyaniline-5-sulfonic acid)-<i>co</i>-aniline). Ultraviolet–visible (UV-vis) spectroscopic measurements with both components in solution reveal electron transfer from the hypoxanthine (HX)-reduced enzyme to the polymer. The enzyme shows bioelectrocatalytic activity on indium tin oxide (ITO) electrodes, when the polymer is present. Depending on solution pH, different processes can be identified. It can be demonstrated that not only product-based communication with the electrode but also efficient polymer-supported bioelectrocatalysis occur. Interestingly, substrate-dependent catalytic currents can be obtained in acidic and neutral solutions, although the highest activity of XDH with natural reaction partners is in the alkaline region. Furthermore, operation of the enzyme electrode without addition of the natural cofactor of XDH is feasible. Finally, macroporous ITO electrodes have been used as an immobilization platform for the fabrication of HX-sensitive electrodes. The study shows that the efficient polymer/enzyme interaction can be advantageously combined with the open structure of an electrode material of controlled pore size, resulting in good processability, stability, and defined signal transfer in the presence of a substrate