TY - JOUR A1 - Göbel, Gero A1 - Talke, Anja A1 - Ahnert, Uwe A1 - Lisdat, Fred T1 - Electrochemical Activity Determination of Catechol-O-methyl Transferase by Selective Dopamine Detection JF - ChemElectroChem N2 - For the treatment of Parkinson's disease, as one of the most frequent diseases of the central nervous system, several key enzymes for dopamine metabolism [e. g. catechol-O-methyl transferase (COMT)] are drug targets. For an efficient and long-lasting treatment, the activity of this enzyme should be monitored. In this study, an electrochemical approach using differential pulse voltammetry (DPV) is introduced for the activity determination. The applied electrode material, fluorine-doped tin oxide (FTO), is characterized by a clear discrimination between substrate and product of COMT, a high stability of the dopamine signal during consecutive measurements, and a linear dependency on the dopamine concentration in the range of the maximum reaction rate of COMT. Despite these advantageous results, dopamine detection in the complete activity assay is influenced by each of the added essential assay components, even though none of the added components reveal a current signal at the FTO electrode itself. After adjusting the potential range and the assay composition, these effects can be circumvented. By following the dopamine concentrations during COMT action, it can be shown that the activity of COMT can be detected by using differential pulse voltammetry (DPV) at an FTO electrode and, by analyzing different COMT amounts, quantification can be demonstrated. KW - catechol-O-methyl transferase KW - dopamine KW - flow system KW - fluorine-doped tin oxide KW - sensing Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13900 VL - 6 IS - 17 SP - 4533 EP - 4540 PB - Wiley ER - TY - JOUR A1 - Khalid, Waqas A1 - Göbel, Gero A1 - Hühn, Dominik A1 - Montenegro, Jose-Maria A1 - Rivera-Gil, Pilar A1 - Lisdat, Fred A1 - Parak, Wolfgang J. T1 - Light triggered detection of aminophenyl phosphate with a quantum dot based enzyme electrode JF - Journal of Nanobiotechnology N2 - An electrochemical sensor for p-aminophenyl phosphate (p APP) is reported. It is based on the electrochemical conversion of 4-aminophenol (4AP) at a quantum dot (QD) modified electrode under illumination. Without illumination no electron transfer and thus no oxidation of 4AP can occur. p APP as substrate is converted by the enzyme alkaline phosphatase (ALP) to generate 4AP as a product. The QDs are coupled via 1,4-benzenedithiol (BDT) linkage to the surface of a gold electrode and thus allow potential-controlled photocurrent generation. The photocurrent is modified by the enzyme reaction providing access to the substrate detection. In order to develop a photobioelectrochemical sensor the enzyme is immobilized on top of the photo-switchable layer of the QDs. Immobilization of ALP is required for the potential possibility of spatially resolved measurements. Geometries with immobilized ALP are compared versus having the ALP in solution. Data indicate that functional immobilization with layer-by-layer assembly is possible. Enzymatic activity of ALP and thus the photocurrent can be described by Michaelis- Menten kinetics. p APP is detected as proof of principle investigation within the range of 25 μM - 1 mM. Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-5808 SN - 1477-3155 VL - 9 IS - 46 ER - TY - JOUR A1 - Göbel, Gero A1 - Dietz, T. A1 - Lisdat, Fred T1 - Biosensor based on an oxygen reducing bilirubin oxidase electrode JF - Procedia Chemistry N2 - An oxygen reducing electrode made of bilirubin oxidase and multi-walled carbon nanotubes (BOD-MWCNT-Au electrode) is coupled to enzymes catalysing oxygen-consuming reactions such as glucose oxidase (GOD) to result in a membrane-free bienzyme electrode. The feasibility of such a molecularly assembled system stabilized by covalent linkage has been demonstrated. The electrochemical characterisation of the bienzyme electrode reveals sensitivity to the enzyme substrate. The results indicate that the BOD-electrode provides a suitable platform for sensing analytes for which oxidases of high activity are available. KW - bienzyme sensor KW - bilirubin oxidase KW - carbon nanotube KW - membran-free KW - mediator-less Y1 - 2009 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-6237 SN - 1876-6196 VL - 1 IS - 1 SP - 273 EP - 276 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 - 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 - 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 - CHAP A1 - Riedel, Marc A1 - Göbel, Gero A1 - Parak, Wolfgang J. A1 - Lisdat, Fred T1 - Light-addressable amperometric electrodes for enzyme sensors based on direct quantum dot-electrode contacts N2 - Quantum dots allow the generation of charge carriers upon illumination. When these particles are attached to an electrode a photocurrent can be generated. This allows their use as a light-switchable layer on the surface. The QDs can not only exchange electronics with the electrode, but can also interact with donor or acceptor compounds in solution providing access to the construction of signal chains starting from an analytic molecule. The magnitude and the direction of the photocurrent depend on several factors such as electrode polarization, solution pH and composition. These defined dependencies have been evaluated with respect to the combination of QD-electrodes with enzyme reactions for sensorial purpose. CdSe/ZnS-QD-modified electrodes can be used to follow enzymatic reactions in solution based on the oxygen sensitivity. In order to develop a photoelectrochemical biosensor, e.g. glucose oxidase is immobilized on the CdSe/ZnS-electrode. One immobilization strategy applies the layer-by-layer-technique of GOD and a polyelectrolyte. Photocurrent measurements of such a sensor show a clear concentration dependent behavior. The principle of combing QD oxidase. The sensitivity of quantum dot electrodes can be influenced by additional nanoparticles, but also by multiple layers of the QDs. In another direction of research it can be influenced by additional nanoparticles, but also by multiple layers of the QDs. In another direction of research it can be demonstrated that direct electron transfer from excited quantum dots can be achieved with the redox protein cytochrome c. This allows the detection of the protein, but also interaction partners such as a enzymes or superoxide. KW - quantum dot electrode KW - enzyme sensor KW - signal chain KW - photobioelectrochemistry KW - light adressability Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-15266 SP - 195 EP - 200 PB - Society of Photo-Optical Instrumentation Engineers (SPIE) ER -