TY - GEN A1 - Tanne, Johannes A1 - Schäfer, Daniel A1 - Khalid, Waqas A1 - Parak, Wolfgang J. A1 - Lisdat, Fred T1 - Lichtgesteuerter bioelektrochemischer Sensor basierend auf CdSe/ZnS-Quantum Dots T2 - Wissenschaftliche Beiträge 2012 N2 - Diese Studie beschäftigt sich mit der Untersuchung der Sauerstoffsensitivität von QD-Elektroden auf Basis von CdSe/ZnS-Nanopartikeln. Das Verhalten des sauerstoffabhängigen Photostroms wurde dabei in Abhängigkeit des pH-Wertes und des Potentials untersucht. Auf Grundlage dieser Sauerstoffabhängigkeit wurde die Enzymaktivität von GOD über Photostrommessungen evaluiert. Für die Konstruktion eines photobioelektrochemischen Sensors, der durch Beleuchtung der entsprechenden Elektrodenfläche ausgelesen werden kann, wurden Multischichten auf die CdSe/ZnS-modifizierten Elektroden aufgetragen. Die Layer-by-Layer Deposition von GOD mit Hilfe des Polyelektrolyten PAH zeigte, dass eine Sensorkonstruktion möglich ist. Die Sensoreigenschaften dieser Elektroden werden drastisch durch die Menge an immobilisiertem Enzym auf der Quantum Dot-Schicht beeinflusst. Durch die Präparation von vier Bilayern [GOD/PAH]4 an CdSe/ ZnS Elektroden kann ein schnell ansprechbarer Sensor für Konzentrationen zwischen 0.1 – 5 mM Glukose hergestellt werden. Dies eröffnet neue Möglichkeiten für die Multianalytdetektion mit nichtstrukturierten Sensorelektroden, lokalisierten Enzymen und räumlich aufgelöster Auslesung durch Licht. N2 - This study reports on the oxygen sensitivity of quantum dot electrodes modified with CdSe/ZnS nanocrystals. The photocurrent behaviour is analysed in dependence on pH and applied potential by potentiostatic and potentiodynamic measurements. On the basis of the influence of the oxygen content in solution on the photocurrent generation the enzymatic activity of GOD is evaluated in solution. In order to construct a photobioelectrochemical sensor which can be read out by illuminating the respective electrode area multilayers were build up on the CdSe/ZnS-modified electrodes. The layer-by-layer deposition of GOD by means of the polyelectrolyte PAH show that a sensor construction is possible. The sensing properties of such kind of electrodes are drastically influenced by the amount and density of the enzyme on top of the quantum dot layer. By depositing 4 bilayers [GOD/ PAH]4 on the CdSe/ZnS electrode a fast responding sensor for the concentration range 0.1mM-5mM glucose can be prepared. This opens the door to a multianalyte detection with a non-structured sensing electrode, localized enzymes and spatial read-out by light. Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus-1357 SN - 0949-8214 VL - 16 SP - 15 EP - 22 ER - TY - JOUR A1 - Morlock, Sascha A1 - Subramanian, Senthil Kumar A1 - Zouni, Athina A1 - Lisdat, Fred T1 - Closing the green gap of photosystem I with synthetic fluorophores for enhanced photocurrent generation in photobiocathodes JF - Chemical Science N2 - One restriction for biohybrid photovoltaics is the limited conversion of green light by most natural photoactive components. The present study aims to fill the green gap of photosystem I (PSI) with covalently linked fluorophores, ATTO 590 and ATTO 532. Photobiocathodes are prepared by combining a 20 μm thick 3D indium tin oxide (ITO) structure with these constructs to enhance the photocurrent density compared to setups based on native PSI. To this end, two electron transfer mechanisms, with and without a mediator, are studied to evaluate differences in the behavior of the constructs. Wavelength-dependent measurements confirm the influence of the additional fluorophores on the photocurrent. The performance is significantly increased for all modifications compared to native PSI when cytochrome c is present as a redox-mediator. The photocurrent almost doubles from −32.5 to up to −60.9 μA cm−2. For mediator-less photobiocathodes, interestingly, drastic differences appear between the constructs made with various dyes. While the turnover frequency (TOF) is doubled to 10 e−/PSI/s for PSI-ATTO590 on the 3D ITO compared to the reference specimen, the photocurrents are slightly smaller since the PSI-ATTO590 coverage is low. In contrast, the PSI-ATTO532 construct performs exceptionally well. The TOF increases to 31 e−/PSI/s, and a photocurrent of −47.0 μA cm−2 is obtained. This current is a factor of 6 better than the reference made with native PSI in direct electron transfer mode and sets a new record for mediator-free photobioelectrodes combining 3D electrode structures and light-converting biocomponents. Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-17022 VL - 14 SP - 1696 EP - 1708 PB - Royal Society of Chemistry (RSC) ER - TY - JOUR A1 - Morlock, Sascha A1 - Subramanian, Senthil Kumar A1 - Zouni, Athina A1 - Lisdat, Fred T1 - Bio-inorganic hybrid structures for direct electron transfer to photosystem I in photobioelectrodes JF - Biosensors and Bioelectronics N2 - Synthetic materials can be combined with biological components in many ways. One example that provides scientists with multiple challenges is a photobioelectrode that converts sunlight into electrons in a biohybrid approach. In the present study several key parameters are evaluated concerning their influence on the direct electron transfer from a 3D indium tin oxide (ITO) electrode material to photosystem I (PSI) as a light-harvesting biomolecule. In contrast to previous investigations, no mediating molecule is added to shuttle the electrons to the luminal side of PSI. Thus, this setup is less complex than foregoing ones. The solution composition drastically influences the interaction of PSI with the ITO surface. Here, the application of higher buffer concentrations and the addition of salts are advantageous, whereas the nature of the buffer ions plays a minor role. The artificial electrode material's thickness is adjustable since a spin-coating procedure is used for preparation. With a 30 μm thick structure and immobilized PSI cathodic photocurrents up to 10.1 μA cm−2 are obtained at 100 mW cm−2 illumination intensity and an applied potential of −0.1V vs. Ag/AgCl. Over a period of three days the photobioelectrodes are illuminated for a total of 90 min and stored between the measurements at ambient temperature. The stability of the setup is noteworthy as still about 90% of the photocurrent is retained. The photocathode described here offers many positive features, including a high onset potential for the photocurrent starting sligthly above the redox potentail of P700, and applicability in a wide pH range from pH 5 to 8. Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-16770 SN - 1873-4235 VL - 204 PB - Elsevier ER - TY - JOUR A1 - Heinsohn, Natascha Katharina A1 - Niedl, Robert Raimund A1 - Anielski, Alexander A1 - Lisdat, Fred A1 - Beta, Carsten T1 - Electrophoretic µPAD for Purification and Analysis of DNA Samples JF - Biosensors N2 - In this work, the fabrication and characterization of a simple, inexpensive, and effective microfluidic paper analytic device (µPAD) for monitoring DNA samples is reported. The glass microfiber-based chip has been fabricated by a new wax-based transfer-printing technique and an electrode printing process. It is capable of moving DNA effectively in a time-dependent fashion. The nucleic acid sample is not damaged by this process and is accumulated in front of the anode, but not directly on the electrode. Thus, further DNA processing is feasible. The system allows the DNA to be purified by separating it from other components in sample mixtures such as proteins. Furthermore, it is demonstrated that DNA can be moved through several layers of the glass fiber material. This proof of concept will provide the basis for the development of rapid test systems, e.g., for the detection of pathogens in water samples. KW - microfluidic paper analytic device (µPAD) KW - patterning glass microfiber KW - fiber-electrophoresis chip KW - DNA KW - imprinted electrodes KW - cross layer chip KW - polymerase chain reaction (PCR) KW - purification Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-15763 SN - 2079-6374 VL - 12 IS - 2 PB - MDPI ER - TY - JOUR A1 - Kallabis, Conrad A1 - Beyerlein, Peter A1 - Lisdat, Fred T1 - Quantitative determination of dopamine in the presence of interfering substances supported by machine learning tools JF - Bioelectrochemistry N2 - In the field of neuroscience as well as in the clinical setting, the neurotransmitter dopamine (DA) is an analyte which is important for research as well as medical purposes. There are plenty of methods available to measure dopamine quantitatively, with voltammetric ones such as differential pulse voltammetry (DPV) being among the most convenient and simple ones. However, dopamine often occurs, either naturally or because of the requirements of involved enzymatic systems, alongside substances that can influence the signal it produces upon electrochemical conversion. An example for such substances is the magnesium ion, which itself is not electrochemically active in the potential range needed for DA oxidation, but influences the dopamine signal. We have characterized the properties of DPV signals subject to the interaction between DA and Mg2+ and show that, although these properties are changing in a nonlinear fashion when both concentrations are varying, relatively simple linear mathematical models can be used to determine dopamine concentrations quantitatively in the presence of magnesium ions. The focus of this study is thus, the mathematical treatment of experimental data in order to overcome an analytical problem and not the investigation of the chemical background of DA-Mg2+ interaction. KW - dopamine KW - voltammetric detection KW - interference KW - magnesium ion KW - multiple linear regression KW - Bayesian linear regression KW - multivariate calibration models Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-19277 SN - 1567-5394 VL - 157 IS - 108667 ER - TY - JOUR A1 - Göbel, Gero A1 - Müller, Florian A1 - Talke, Anja A1 - Ahnert, Uwe A1 - Lisdat, Fred T1 - Qualitative and quantitative protease activity tests based on protein degradation in three-dimensional structures JF - Bioelectrochemistry N2 - The pattern of the activity of proteases is related to distinct physiological states of living organisms. Often activity changes of a certain protease can be assigned to a specific disease. Hence, they are useful biomarkers and a simple and fast determination method of their activity could be a valuable tool for the efficient monitoring of numerous diseases. Here, two different methods for the qualitative and quantitative determination of protease activity are demonstrated using the model system of proteinase K. The first test system is based on a protein-modified and colored 3D silica structure that changes color when exposed to the enzyme. This method has also been used for the detection of matrix metallo-protease 2 (MMP2) with gelatine as protease substrate on the plates. The second detection system uses the decrease in the voltammetric signal of a cytochrome c/DNA multilayer electrode after incubation with a protease to quantitatively determine its proteolytic activity. While activities down to 0.15 U/ml can be detected with the first method, the second one provides detection limits of about 0.03 U/ml (for proteinase K.) The functionality of both systems can be demonstrated and ways for further enhancement of sensitivity have been elucidated. KW - multilayer electrode KW - protease activity KW - proteinase K KW - silica gel Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-19294 SN - 1567-5394 VL - 160 ER - TY - JOUR A1 - Morlock, Sascha A1 - Subramanian, Senthil Kumar A1 - Zouni, Athina A1 - Lisdat, Fred T1 - Scalable Three-Dimensional Photobioelectrodes Made of Reduced Graphene Oxide Combined with Photosystem I JF - ACS Applied Materials & Interfaces N2 - Photobioelectrodes represent one of the examples where artificial materials are combined with biological entities to undertake semi-artificial photosynthesis. Here, an approach is described that uses reduced graphene oxide (rGO) as an electrode material. This classical 2D material is used to construct a three-dimensional structure by a template-based approach combined with a simple spin-coating process during preparation. Inspired by this novel material and photosystem I (PSI), a biophotovoltaic electrode is being designed and investigated. Both direct electron transfer to PSI and mediated electron transfer via cytochrome c from horse heart as redox protein can be confirmed. Electrode preparation and protein immobilization have been optimized. The performance can be upscaled by adjusting the thickness of the 3D electrode using different numbers of spin-coating steps during preparation. Thus, photocurrents up to ∼14 μA/cm2 are measured for 12 spin-coated layers of rGO corresponding to a turnover frequency of 30 e– PSI–1 s–1 and external quantum efficiency (EQE) of 0.07% at a thickness of about 15 μm. Operational stability has been analyzed for several days. Particularly, the performance at low illumination intensities is very promising (1.39 μA/cm2 at 0.1 mW/cm2 and −0.15 V vs Ag/AgCl; EQE 6.8%). KW - biophotovoltaics KW - reduced graphene oxide (rGO) KW - scalable template process KW - spin-coating KW - 3D electrode structure KW - carbon material Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-16760 VL - 13 IS - 9 SP - 11237 EP - 11246 PB - American Chemical Society (ACS) ER - TY - GEN A1 - Lisdat, Fred A1 - Beissenhirtz, Moritz K. A1 - Scheller, Frieder W. A1 - Viezzoli, Maria S. T1 - Cystein-Mutanten der Cu,Zn-Superoxiddismutase und ihre Anwendung in Proteinelektroden für die Detektion von freien Sauerstoffradikalen T2 - Wissenschaftliche Beiträge 2006 N2 - Das Enzym Superoxiddismutase (SOD) bietet wegen seiner hohen Reaktionsrate und seiner extrem hohen Substratspezifi tät große Vorteile für eine Anwendung als Superoxidbiosensor. In dieser Arbeit wurden durch molekularbiologische Methoden Mutanten der humanen Cu,Zn-SOD gewonnen, welche ein oder zwei zusätzliche Cystein-Reste enthielten, die eine einfache Immobilisierung des Proteins durch Bindung des Cystein-Schwefels auf Goldelektroden ermöglichten. Sechs solcher Mutanten wurden entworfen, exprimiert, aufgereinigt und elektrochemisch charakterisiert. Alle Mutanten konnten durch einen einfachen Inkubationsschritt auf Goldelektroden gebunden werden und zeigten ein quasi-reversibles elektrochemisches Ansprechen. Für eine Mutante wurde die Anwendung als Superoxidsensor genauer untersucht und für beide Teilreaktionen der Dismutation ein Ansprechen des Sensors auf das Radikal gefunden. Bei Verwendung einer Teilreaktion konnte die Empfindlichkeit herkömmlicher Monoschichtsensoren um etwa eine Größenordnung übertroffen werden. Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus-216 SN - 0949-8214 VL - 11 SP - 7 EP - 11 ER - TY - GEN A1 - Schubart, Ivo A1 - Göbel, Gero A1 - Lisdat, Fred T1 - Direkte Kontaktierung des Enzyms (PQQ)-GDH und Elektroden mit Hilfe von polymermodifizierten Nanoröhren für die Anwendung in Biobrennstoffzellen T2 - Wissenschaftliche Beiträge 2013 N2 - In dieser Studie präsentieren wir eine Enzymelektrode, bei der ein direkter Elektronentransfer (DET) zwischen der Pyrrolochinolinchinon-abhängigen Glukosedehydrogenase (PQQ)-GDH und einer Elektrode realisiert werden konnte. Hierfür wird eine Goldelektrode mit mehrwandigen Kohlenstoffnanoröhren [engl. multi-walled carbon nanotubes (MWCNT)] modifiziert, anschließend mit einem Copolymer aus Anilinderivaten überzogen und dann die (PQQ)-GDH (Acinetobacter calcoaceticus) kovalent immobilisiert. Die gepulste Polymersynthese wird hinsichtlich der Effektivität der bioelektrokatalytischen Umsetzung von Glukose optimiert. Die Glukoseoxidation startet bei einem Potential von -0,1 V vs. Ag/AgCl (1 M KCl) und Stromdichten von bis zu 500 μA/cm² (+0,1 V) können erreicht werden. Der Messbereich für Glukose liegt bei 0,1-5 mM (+0,1 V vs. Ag/AgCl). Der dynamische Bereich ist bei höherem Potential auf bis zu 100 mM (+0,4 V vs Ag/AgCl) erweitert. Die Elektrode wird als Anode in einer Biobrennstoffzelle (BBZ) mit einer Bilirubinoxidase-modifizierten MWCNT/Gold-Kathode eingesetzt. Beide Elektroden basieren auf einem DET. Das Zellpotential der BBZ beträgt 680 ±20 mV und sie erreicht eine maximale Leistungsdichte von 65 μW/cm² (bei einer Zellspannung von 350 mV). Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-3127 SN - 0949-8214 VL - 17 SP - 17 EP - 22 ER - TY - GEN A1 - Bütow, Sandra M. A1 - Pänke, Oliver A1 - Kafka, Jan A1 - Lisdat, Fred T1 - Goldchipelektroden zur elektrochemischen DNA-Detektion T2 - Wissenschaftliche Beiträge 2008 N2 - Im folgenden Artikel werden einfache DNA-Sensoren vorgestellt, mit deren Hilfe es durch voltammetrische und impedimetrische Messmethoden möglich ist, schnell, sensitiv und kostengünstig Einzelstrang-DNA (ssDNA) nachzuweisen. Beide Messprinzipien lassen neben der spezifischen Detektion auch die Quantifizierung von DNA-Sequenzen sowie den Nachweis von einzelnen Basenfehlpaarungen innerhalb dieser Sequenzen zu. Fänger- DNA wurde zu diesem Zweck mit dem 5’-Ende auf einer Goldoberfläche immobilisiert. Die Hybridisierung mit einem Methylenblau (MB) markierten oder unmarkierten Probenstrang konnte dann mit Hilfe der Differenzpulsvoltammetrie DPV oder der elektrochemischen Impedanzspektroskopie nachgewiesen werden. Die voltammetrische Quantifizierung erfolgte in einem direkten und kompetitiven Ansatz, mit einem Detektionslimit von 30 nM bzw. 3 nM (bei Einsatz von 0,1 μM Kompetitor- DNA). Das Detektionslimit beim impedimetrischen Nachweis lag bei 100 nM DNA. Die hier vorgestellten Sensoren sind zum einen regenerierbar und können zum anderen über einen Zeitraum von zwei Monaten gelagert werden. N2 - This paper describes simplistic electrochemical DNA sensors for the sensitive, more rapid and cost effective detection of single-stranded DNA (ssDNA). The used methodes are the voltammetric detection and the detection by impedance spectroscopy. Beside the specific detection of ssDNA both techniques allow quantification of DNA and verification of single base pair mismatches within the sequences. Therefore a single-stranded 18mer oligonucleotide (DNA) was immobilised via a thiol-linker on gold film electrodes and served as probe DNA. Hybridisation was detected by means of the electroactive redox-marker methylene blue (MB), which was covalently bound to the 5’-end of the target DNA, by differential pulse voltammetry (DPV) or by measuring the differences in the charge transfer resistance (RCT) by electrochemical impedance spectroscopy (EIS) using non-labelled ssDNA targets. MB-labelled target DNA was verified down to 30 nM DNA. By application of a competitive binding assay non-labelled DNA was detected down to 3 nM DNA. The detection limit for impedimetric DNA sensors was 100 nM ssDNA. The sensors were found to be reusable and could be stored for more than two month at 4 °C without significant loss in their activity. Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus-653 SN - 0949-8214 VL - 13 SP - 25 EP - 34 ER - TY - GEN A1 - Schubert, Kirsten A1 - Khalid, Waqas A1 - Yue, Zhao A1 - Parak, Wolfgang J. A1 - Lisdat, Fred T1 - Halbleiternanopartikel-modifizierte Elektrode zum Nachweis von Substraten von NADH-abhängigen Enzymreaktionen T2 - Wissenschaftliche Beiträge 2009/2010 N2 - Es wurde ein Elektrodensystem entwickelt, das aufbauend auf Halbleiternanopartikeln (so genannte Quantenpunkte) die sensitive Detektion des Enzymkofaktors NADH (nicotinamide adenine dinucleotide) erlaubt. Kolloidale halbleitende CdSe/ZnS-Nanokristalle sind durch ein Dithiol über Chemisorption an Gold gebunden. Das Stromsignal kann durch die Beleuchtung der Quantenpunkt modifizierten Oberfläche beeinflusst werden. Durch Photoanregung entstehen Elektron-Loch- Paare in den Nanopartikeln, die als anodischer oder kathodischer Photostrom detektiert werden können. Die Immobilisierung der Nanokristalle ist durch amperometrische Photostrom- und Quarzmikrowaage-Messungen (quartz crystal microbalance) verifiziert. Diese Studie zeigt, dass CdSe/ZnS-Quantenpunktmodifizierte Elektroden eine konzentrationsabhängige NADH-Detektion im Bereich von 20μM bis 2mM bei relativ niedrigem Potential (um 0V vs Ag/AgCl, 1 M KCl) ermöglichen. Somit können solche Elektroden in Kombination mit NADH-produzierenden Reaktionen für die lichtgesteuerte Analyse der entsprechenden Substrate des Biokatalysators genutzt werden. Es wird gezeigt, dass mit einem solchen Elektrodensystem und Photostrommessungen ein Glukosenachweis möglich ist. N2 - An electrode system based on semiconductive nanoparticles (so called quantum dots) was developed which allows the sensitive detection of the enzyme cofactor NADH (nicotinamide adenine dinucleotide). Colloidal semiconductive CdSe/ZnS nanocrystals are bound to gold via a dithiol compound by chemisorption. The current signal can be influenced by illumination of the quantum dot-modified electrode surface. Because of photoexcitation electron-holepairs are generated in the nanoparticles which can be detected as anodic or cathodic photocurrent. The immobilisation of the nanocrystals is verified by photocurrent and quarz crystal microbalance (QCM) measurements. This study shows that CdSe/ZnS-quatum dot-modified electrodes provide a concentration-dependent detection of NADH in the range of 20μM up to 2mM at relatively low overpotentials (around 0V vs Ag/ AgCl, 1 M KCl). Such electrodes can be used in combination with NADH-producing reactions for the lighttriggered analysis of the corresponding substrate of the biocatalyst. The detection of glucose with such an electrode system and photocurrent measurements is shown. Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus-810 SN - 0949-8214 VL - 14 SP - 13 EP - 22 ER - TY - GEN A1 - Tanne, Christoph K. A1 - Göbel, Gero A1 - Lisdat, Fred T1 - Entwicklung einer Glucosedehydrogenase-basierten Anode und deren Anwendung in einer Glucose/O2-Biobrennstoffzelle T2 - Wissenschaftliche Beiträge 2011 N2 - Unter Verwendung von mehrwandigen Kohlenstoffnanoröhren wurde in dieser Studie eine neuartige Anode zum Einsatz in Biobrennstoffzellen entwickelt. Dazu wurde das rekombinante Enzym Pyrrolochinolinchinon(PQQ)- abhängige Glucosedehydrogenase kovalent an eine aus PQQ bestehenden Zwischenschicht gekoppelt, welche zuvor an die Kohlenstoffnanoröhren adsorbiert war. Die Nanoröhren wurden aufgrund ihrer Thiolmodifikation chemisorptiv auf einer Goldelektrode gebunden. In glucosehaltiger Lösung konnte der Start eines katalytischen Stroms bei einem Potential von -80 mV vs. Ag/AgCl (1 MKCl) beobachtet werden. Unter Substratsättigung wurden Stromdichten im Bereich von 170 bis 200 μA/cm2 gemessen. Dieses System basiert auf einem mediatorvermittelten Elektronentransfer. Die entwickelte (PQQ)-GDH-MWCNT-Elektrode wurde mit einer MWCNT-modifizierten Elektrode kombiniert, bei der Bilirubinoxidase (BOD) als Biokatalysator fungiert. Daraus resultierte eine membranfreie Biobrennstoffzelle mit einem leichgewichtspotential von 600 mV und Leistungsdichten im Bereich von 20-25 μW/cm2. N2 - In this study a biofuel cell anode is developed on the basis of multi-walled carbon nanotubes (MWCNTs). Recombinant pyrroloquinoline quinone (PQQ) dependent glucose dehydrogenase is covalently coupled to a PQQ-layer which is adsorbed onto thiolmodified MWCNTs. The MWCNTs are chemisorbed to a gold electrode. In the presence of glucose a catalytic current starts at a potential of -80 mV vs. Ag/AgCl, 1 M KCl. Under substrate saturation current densities of 170 to 200 μA/cm2 can be achieved. The operation is based on mediated electron transfer of the enzyme. This (PQQ)-GDH-MWCNT-electrode is combined with a MWCNT-modifi ed electrode to which bilirubin oxidase (BOD) is covalently coupled. The resulting membrane-free biofuel cell has an open cell potential of 600 mV and can achieve power densities in the range of 20-25 μW/cm2. Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus-1039 SN - 0949-8214 VL - 15 SP - 13 EP - 21 ER - TY - JOUR A1 - Tanne, Johannes A1 - Kracher, Daniel A1 - Dietzel, Birgit A1 - Schulz, Burkhard A1 - Ludwig, Roland A1 - Lisdat, Fred A1 - Scheller, Frieder W. A1 - Bier, Frank Fabian T1 - Carboxylated or Aminated Polyaniline—Multiwalled Carbon Nanotubes Nanohybrids for Immobilization of Cellobiose Dehydrogenase on Gold Electrodes JF - Biosensors N2 - Polymer-multiwalled carbon nanotube (MWCNT) nanohybrids, which differ in surface charge have been synthesized to study the bioelectrocatalysis of adsorbed cellobiose dehydrogenase (CDH) from Phanerochaete sordida on gold electrodes. To obtain negatively charged nanohybrids, poly(3-amino-4-methoxybenzoic acid-co-aniline) (P(AMB-A)) was covalently linked to the surface of MWCNTs while modification with p-phenylenediamine (PDA) converted the COOH-groups to positively charged amino groups. Fourier transform infrared spectroscopy (FTIR) measurements verified the p-phenylenediamine (PDA) modification of the polymer-CNT nanohybrids. The positively charged nanohybrid MWCNT-P(AMB-A)-PDA promoted direct electron transfer (DET) of CDH to the electrode and bioelectrocatalysis of lactose was observed. Amperometric measurements gave an electrochemical response with KMapp = 8.89 mM and a current density of 410 nA/cm2 (15 mM lactose). The catalytic response was tested at pH 3.5 and 4.5. Interference by ascorbic acid was not observed. The study proves that DET between the MWCNT-P(AMB-A)-PDA nanohybrids and CDH is efficient and allows the sensorial detection of lactose. KW - multiwalled carbon nanotube KW - polyaniline KW - nanohybrids KW - cellobiose dehydrogenase Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-5826 SN - 2079-6374 VL - 4 IS - 4 SP - 370 EP - 386 ER - TY - JOUR A1 - Kölsch, Adrian A1 - Radon, C. A1 - Golub, M. A1 - Baumert, A. A1 - Bürger, Jörg A1 - Mielke, Thorsten A1 - Lisdat, Fred A1 - Feoktystov, Artem A1 - Pieper, Jörg A1 - Zouni, Athina A1 - Wendler, Petra T1 - Current limits of structural biology: The transient interaction between cytochrome c6 and photosystem I JF - Current Research in Structural Biology N2 - Trimeric photosystem I from the cyanobacterium Thermosynechococcus elongatus (TePSI) is an intrinsic membrane protein, which converts solar energy into electrical energy by oxidizing the soluble redox mediator cytochrome c6 (Cyt c6) and reducing ferredoxin. Here, we use cryo-electron microscopy and small angle neutron scattering (SANS) to characterize the transient binding of Cyt c6 to TePSI. The structure of TePSI cross-linked to Cyt c6 was solved at a resolution of 2.9 Å and shows additional cofactors as well as side chain density for 84% of the peptide chain of subunit PsaK, revealing a hydrophobic, membrane intrinsic loop that enables binding of associated proteins. Due to the poor binding specificity, Cyt c6 could not be localized with certainty in our cryo-EM analysis. SANS measurements confirm that Cyt c6 does not bind to TePSI at protein concentrations comparable to those for cross-linking. However, SANS data indicate a complex formation between TePSI and the non-native mitochondrial cytochrome from horse heart (Cyt cHH). Our study pinpoints the difficulty of identifying very small binding partners (less than 5% of the overall size) in EM structures when binding affinities are poor. We relate our results to well resolved co-structures with known binding affinities and recommend confirmatory methods for complexes with KM values higher than 20 μM. KW - photosystem I KW - cryo-EM KW - Thermosynechococcus elongatus KW - small angle neutron scattering KW - cytochrome c6 KW - electron transfer KW - photo-biotechnology Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13628 SN - 2665-928X VL - 2 SP - 171 EP - 179 ER - TY - GEN A1 - Tersch, Christoph A1 - Lisdat, Fred T1 - Labelfreie Detektion von Protein-DNA-Interaktionen durch elektrochemische Impedanzspektroskopie T2 - Wissenschaftliche Beiträge 2012 N2 - Es wird ein impedimetrisches Sensorsystem für den Nachweis von Protein-DNA-Wechselwirkungen vorgestellt. Der Sensor nutzt kurze Thiol-markierte DNA (ssDNA), die über Chemisorption auf Goldchipelektroden immobilisiert wird. Aus den Impedanzspektren wurde der Durchtrittswiderstand (Rct) als Kenngröße für die zu untersuchenden Wechselwirkungen gewählt. In Anwesenheit des Redoxsystems Ferro-/Ferrycyanid konnte eine Zunahme des Durchtrittswiderstandes nach der Immobilisierung und anschließender Hybridisierung auf der Sensoroberfl äche registriert werden. Der Einsatz längerer Fänger-DNA (25-mer im Vergleich zu 18-mer) führte zu einer Abnahme der Konzentration an immobilisierten Fänger-Strängen, aber auch zu einer Vergrößerung der Durchtrittswiderstände sowohl für ssDNA als auch dsDNA. Bei ähnlichen Oberflächenkonzentrationen ließ sich eine annähernd gleiche Sensitivität des Hybridisierungsnachweises im Vergleich zu 18-mer Fänger-Strängen erzielen. Mit Hilfe des Elektrodensystems wurde die Nachweisbarkeit von Protein-DNA-Wechselwirkungen untersucht. Die Restriktion doppelsträngiger DNA durch die Restriktionsendonuklease BamHI konnte mit der Zyklovoltammetrie und markierungsfrei mit der Impedanzspektroskopie verfolgt werden. Des Weiteren wurde die sequenzspezifische Bindung des Transkriptionsfaktors NF-κB p50 anhand einer Abnahme von Rct impedimetrisch registriert. N2 - In this work, the applicability of an impedimetric DNA sensor has been investigated for the detection of protein- DNA interactions. The sensor is based on short thiol-modified single-stranded DNA, which is chemisorbed to gold chip electrodes. In the presence of the redox system ferri-/ferrocyanide impedance measurements show an increase in charge transfer resistance after immobilization and hybridization of ssDNA to the sensor surface. The use of a longer capture oligonucleotide (a 25-mer instead of an 18-mer) results in a decreasing probe concentration on the surface. Furthermore it causes an increase of the charge transfer resistance for both ssDNA and dsDNA. The hybridization event, however, can be detected with a similar sensitivity compared to an 18-mer (with the same surface concentration) and allows a good discrimination between ssDNA and dsDNA. This electrode system is used to follow an enzyme reaction on the surface electrochemically. The cleavage of a double-stranded DNA by restriction endonuclease BamHI could be verified by cyclic voltammetry and impedance spectroscopy. The sequence specific DNAbinding of the transcription factor NF-κB p50 is found to cause a decrease in charge transfer resistance. Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus-1346 SN - 0949-8214 VL - 16 SP - 23 EP - 30 ER - TY - JOUR A1 - Bay, Daniyah H. A1 - Busch, Annika A1 - Lisdat, Fred A1 - Iida, Keisuke A1 - Ikebukuro, Kazunori A1 - Nagasawa, Kazuo A1 - Karube, Isao A1 - Yoshida, Wataru T1 - Identification of G-quadruplex structures that possess transcriptional regulating functions in the Dele and Cdc6 CpG islands JF - BMC Molecular Biology N2 - G-quadruplex is a DNA secondary structure that has been shown to play an important role in biological systems. In a previous study, we identified 1998 G-quadruplex-forming sequences using a mouse CpG islands DNA microarray with a fluorescent-labeled G-quadruplex ligand. Among these putative G-quadruplex-forming sequences, G-quadruplex formation was verified for 10 randomly selected sequences by CD spectroscopy and DMS footprinting analysis. In this study, the biological function of the 10 G-quadruplex-forming sequences in the transcriptional regulation has been analyzed using a reporter assay. KW - Cdc6 KW - Dele KW - G-quadruplex KW - transcriptional regulation KW - 7OTD Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-9811 SN - 1471-2199 VL - 18 IS - 17 ER - TY - JOUR A1 - Zhao, Shuang A1 - Riedel, Marc A1 - Patarroyo, Javier A1 - Bastús, Neus G. A1 - Puntes, Victor A1 - Yue, Zhao A1 - Lisdat, Fred A1 - Parak, Wolfgang J. T1 - Tailoring of the photocatalytic activity of CeO₂ nanoparticles by the presence of plasmonic Ag nanoparticles JF - Nanoscale N2 - The present study investigates basic features of a photoelectrochemical system based on CeO2 nanoparticles fixed on gold electrodes. Since photocurrent generation is limited to the absorption range of the CeO2 in the UV range, the combination with metal nanoparticles has been studied. It can be shown that the combination of silver nanoparticles with the CeO2 can shift the excitation range into the visible light wavelength range. Here a close contact between both components has been found to be essential and thus, hybrid CeO2@Ag nanoparticles have been prepared and analyzed. We have collected arguments that electron transfer occurs between both compositional elements of the hybrid nanoparticles.The photocurrent generation can be rationalized on the basis of an energy diagram underlying the necessity of surface plasmon excitation in the metal nanoparticles, which is also supported by wavelength-dependent photocurrent measurements. However, electrochemical reactions seem to occur at the CeO2 surface and consequently, the catalytic properties of this material can be exploited as exemplified with the photoelectrochemical reduction of hydrogen peroxide. It can be further demonstrated that the layer-by layer technique can be exploited to create a multilayer system on top of a gold electrode which allows the adjustment of the sensitivity of the photoelectrochemical system. Thus, with a 5-layer electrode with hybrid CeO2@Ag nanoparticles submicromolar hydrogen peroxide concentrations can be detected. Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-16361 VL - 14 SP - 12048 EP - 12059 PB - Royal Society of Chemistry (RSC) ER - TY - JOUR A1 - Riedel, Marc A1 - Höfs, Soraya A1 - Ruff, Adrian A1 - Schuhmann, Wolfgang A1 - Lisdat, Fred T1 - A Tandem Solar Biofuel Cell: Harnessing Energy from Light and Biofuels JF - Angewandte Chemie International Edition N2 - We report on a photobioelectrochemical fuel cell consisting of a glucose‐oxidase‐modified BiFeO3 photobiocathode and a quantum‐dot‐sensitized inverse opal TiO2 photobioanode linked to FAD glucose dehydrogenase via a redox polymer. Both photobioelectrodes are driven by enzymatic glucose conversion. Whereas the photobioanode can collect electrons from sugar oxidation at rather low potential, the photobiocathode shows reduction currents at rather high potential. The electrodes can be arranged in a sandwich‐like manner due to the semi‐transparent nature of BiFeO3, which also guarantees a simultaneous excitation of the photobioanode when illuminated via the cathode side. This tandem cell can generate electricity under illumination and in the presence of glucose and provides an exceptionally high OCV of about 1 V. The developed semi‐artificial system has significant implications for the integration of biocatalysts in photoactive entities for bioenergetic purposes, and it opens up a new path toward generation of electricity from sunlight and (bio)fuels. Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13680 SN - 1521-3773 VL - 60 IS - 4 SP - 2078 EP - 2083 PB - Wiley ER - TY - GEN A1 - Gladisch, Johannes A1 - Sarauli, David A1 - Schäfer, Daniel A1 - Dietzel, Birgit A1 - Schulz, Burkhard A1 - Lisdat, Fred T1 - Elektrogesponnene Polymerfasern als neuartiges Material für die Bioelektrokatalyse des Enzyms Pyrrolochinolinchinon-abhängige Glucosedehydrogenase T2 - Wissenschaftliche Beiträge 2016 N2 - 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. N2 - 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. Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-5293 SN - 0949-8214 VL - 20 SP - 15 EP - 21 ER - TY - JOUR A1 - Gladisch, Johannes A1 - Sarauli, David A1 - Schäfer, Daniel A1 - Dietzel, Birgit A1 - Schulz, Burkhard A1 - Lisdat, Fred T1 - Towards a novel bioelectrocatalytic platform based on “wiring” of pyrroloquinoline quinone-dependent glucose dehydrogenase with an electrospun conductive polymeric fiber architecture JF - Scientific Reports N2 - 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. Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-5846 SN - 2045-2322 VL - 6 ER -