TY - JOUR A1 - Zeng, Ting A1 - Pankratov, Dmitry A1 - Falk, Magnus A1 - Leimkühler, Silke A1 - Shleev, Sergey A1 - Wollenberger, Ursula T1 - Miniature direct electron transfer based sulphite/oxygen enzymatic fuel cells JF - Biosensors and bioelectronics : the principal international journal devoted to research, design development and application of biosensors and bioelectronics N2 - A direct electron transfer (DET) based sulphite/oxygen biofuel cell is reported that utilises human sulphite oxidase (hSOx) and Myrothecium verrucaria bilirubin oxidase (MvBOx) and nanostructured gold electrodes. For bioanode construction, the nanostructured gold microelectrodes were further modified with 3,3'-dithiodipropionic acid di(N-hydroxysuccinimide ester) to which polyethylene imine was covalently attached. hSOx was adsorbed onto this chemically modified nanostructured electrode with high surface loading of electroactive enzyme and in presence of sulphite high anodic bioelectrocatalytic currents were generated with an onset potential of 0.05 V vs. NHE. The biocathode contained MyBOx directly adsorbed to the deposited gold nanoparticles for cathodic oxygen reduction starting at 0.71 V vs. NHE. Both enzyme electrodes were integrated to a DET-type biofuel cell. Power densities of 8 and 1 mu W cm(-2) were achieved at 0.15 V and 0.45 V of cell voltages, respectively, with the membrane based biodevices under aerobic conditions. (C) 2014 Elsevier B.V. All rights reserved. KW - Enzymatic fuel cell KW - Microscale electrode KW - Direct electron transfer KW - Sulphite oxidase KW - Bilirubin oxidase Y1 - 2015 U6 - https://doi.org/10.1016/j.bios.2014.10.080 SN - 0956-5663 SN - 1873-4235 VL - 66 SP - 39 EP - 42 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Zeng, Ting A1 - Leimkühler, Silke A1 - Koetz, Joachim A1 - Wollenberger, Ursula T1 - Effective Electrochemistry of Human Sulfite Oxidase Immobilized on Quantum-Dots-Modified Indium Tin Oxide Electrode JF - ACS applied materials & interfaces N2 - The bioelectrocatalytic sulfite oxidation by human sulfite oxidase (hSO) on indium tin oxide (ITO) is reported, which is facilitated by functionalizing of the electrode surface with polyethylenimine (PEI)-entrapped CdS nanoparticles and enzyme. hSO was assembled onto the electrode with a high surface loading of electroactive enzyme. In the presence of sulfite but without additional mediators, a high bioelectrocatalytic current was generated. Reference experiments with only PEI showed direct electron transfer and catalytic activity of hSO, but these were less pronounced. The application of the polyelectrolyte-entrapped quantum dots (QDs) on ITO electrodes provides a compatible surface for enzyme binding with promotion of electron transfer. Variations of the buffer solution conditions, e.g., ionic strength, pH, viscosity, and the effect of oxygen, were studied in order to understand intramolecular and heterogeneous electron transfer from hSO to the electrode. The results are consistent with a model derived for the enzyme by using flash photolysis in solution and spectroelectrochemistry and molecular dynamic simulations of hSO on monolayer-modified gold electrodes. Moreover, for the first time a photoelectrochemical electrode involving immobilized hSO is demonstrated where photoexcitation of the CdS/hSO-modified electrode lead to an enhanced generation of bioelectrocatalytic currents upon sulfite addition. Oxidation starts already at the redox potential of the electron transfer domain of hSO and is greatly increased by application of a small overpotential to the CdS/hSO-modified ITO. KW - human sulfite oxidase KW - direct electrochemistry KW - bioelectrocatalysis KW - photocurrent KW - CdS quantum dots Y1 - 2015 U6 - https://doi.org/10.1021/acsami.5b06665 SN - 1944-8244 VL - 7 IS - 38 SP - 21487 EP - 21494 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Yildirim-Semerci, Cigdem A1 - Benayahu, Dafna A1 - Adamovski, Miriam A1 - Wollenberger, Ursula T1 - An Electrochemical Assay for Monitoring Differentiation of the Osteoblastic Cell Line (MBA-15) on the Sensor Chip JF - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis N2 - An electrochemical assay for the indication of the activity of the cell bound differentiation marker alkaline phosphatase (ALP) is proposed using voltammetry on an in-vitro cell culture. The basis of the assay is cultivation of cells on gold microelectrodes in wells of a microplate, catalytic hydrolysis of p-aminophenyl phosphate by ALP and indication of p-aminophenol oxidation by square wave voltammetry (SWV) with the sensors onto which the cells attached. The morphology of the bone marrow stromal cell line (MBA-15) on the electrode surface was investigated and it exhibited in vitro osteogenic characteristics. Since ALP is expressed on the cell surface in early differentiation stage of osteoblastic cells, its activity was followed after different culture times over a period of 144 h by recording repetitive voltammograms at different time points upon addition of the substrate p-aminophenyl phosphate. The ALP activity was estimated from the signal increase related to formation rate of p-aminophenol and the number of cells. The highest value was measured at 120 h, when the cells reached confluence. The results of the electrochemical activity assay are consistent with the colorimetric acquired value from p-nitrophenol formation rate. KW - Alkaline phosphatase KW - Osteoblast KW - Voltammetry KW - Biomarker KW - p-Aminophenol Y1 - 2015 U6 - https://doi.org/10.1002/elan.201400684 SN - 1040-0397 SN - 1521-4109 VL - 27 IS - 6 SP - 1350 EP - 1358 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Tanne, Johannes A1 - Jeoung, Jae-Hun A1 - Peng, Lei A1 - Yarman, Aysu A1 - Dietzel, Birgit A1 - Schulz, Burkhard A1 - Schad, Daniel A1 - Dobbek, Holger A1 - Wollenberger, Ursula A1 - Bier, Frank Fabian A1 - Scheller, Frieder W. T1 - Direct Electron Transfer and Bioelectrocatalysis by a Hexameric, Heme Protein at Nanostructured Electrodes JF - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis N2 - A nanohybrid consisting of poly(3-aminobenzenesulfonic acid-co-aniline) and multiwalled carbon nanotubes [MWCNT-P(ABS-A)]) on a gold electrode was used to immobilize the hexameric tyrosine-coordinated heme protein (HTHP). The enzyme showed direct electron transfer between the heme group of the protein and the nanostructured surface. Desorption of the noncovalently bound heme from the protein could be excluded by control measurements with adsorbed hemin on aminohexanthiol-modified electrodes. The nanostructuring and the optimised charge characteristics resulted in a higher protein coverage as compared with MUA/MU modified electrodes. The adsorbed enzyme shows catalytic activity for the cathodic H2O2 reduction and oxidation of NADH. KW - HTHP KW - Nanohybrid KW - Poylaniline KW - Multiwalled carbon nanotube Y1 - 2015 U6 - https://doi.org/10.1002/elan.201500231 SN - 1040-0397 SN - 1521-4109 VL - 27 IS - 10 SP - 2262 EP - 2267 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Spricigo, Roberto A1 - Leimkühler, Silke A1 - Gorton, Lo A1 - Scheller, Frieder W. A1 - Wollenberger, Ursula T1 - The Electrically Wired Molybdenum Domain of Human Sulfite Oxidase is Bioelectrocatalytically Active JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - We report electron transfer between the catalytic molybdenum cofactor (Moco) domain of human sulfite oxidase (hSO) and electrodes through a poly(vinylpyridine)-bound [osmium(N,N'-methyl-2,2'-biimidazole)(3)](2+/3+) complex as the electron-transfer mediator. The biocatalyst was immobilized in this low-potential redox polymer on a carbon electrode. Upon the addition of sulfite to the immobilized separate Moco domain, the generation of a significant catalytic current demonstrated that the catalytic center is effectively wired and active. The bioelectrocatalytic current of the wired separate catalytic domain reached 25% of the signal of the wired full molybdoheme enzyme hSO, in which the heme b(5) is involved in the electron-transfer pathway. This is the first report on a catalytically active wired molybdenum cofactor domain. The formal potential of this electrochemical mediator is between the potentials of the two cofactors of hSO, and as hSO can occupy several conformations in the polymer matrix, it is imaginable that electron transfer from the catalytic site to the electrode through the osmium center occurs for the hSO molecules in which the Moco domain is sufficiently accessible. The observation of catalytic oxidation currents at low potentials is favorable for applications in bioelectronic devices. KW - Metalloenzymes KW - Enzyme catalysis KW - Immobilization KW - Osmium Y1 - 2015 U6 - https://doi.org/10.1002/ejic.201500034 SN - 1434-1948 SN - 1099-0682 IS - 21 SP - 3526 EP - 3531 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Peng, Lei A1 - Utesch, Tillmann A1 - Yarman, Aysu A1 - Jeoung, Jae-Hun A1 - Steinborn, Silke A1 - Dobbek, Holger A1 - Mroginski, Maria Andrea A1 - Tanne, Johannes A1 - Wollenberger, Ursula A1 - Scheller, Frieder W. T1 - Surface-Tuned Electron Transfer and Electrocatalysis of Hexameric Tyrosine-Coordinated Heme Protein JF - Chemistry - a European journal N2 - Molecular modeling, electrochemical methods, and quartz crystal microbalance were used to characterize immobilized hexameric tyrosine-coordinated heme protein (HTHP) on bare carbon or on gold electrodes modified with positively and negatively charged self-assembled monolayers (SAMs), respectively. HTHP binds to the positively charged surface but no direct electron transfer (DET) is found due to the long distance of the active sites from the electrode surfaces. At carboxyl-terminated surfaces, the neutrally charged bottom of HTHP can bind to the SAM. For this "disc" orientation all six hemes are close to the electrode and their direct electron transfer should be efficient. HTHP on all negatively charged SAMs showed a quasi-reversible redox behavior with rate constant k(s) values between 0.93 and 2.86 s(-1) and apparent formal potentials E-app(0)' between -131.1 and -249.1 mV. On the MUA/MU-modified electrode, the maximum surface concentration corresponds to a complete monolayer of the hexameric HTHP in the disc orientation. HTHP electrostatically immobilized on negatively charged SAMs shows electrocatalysis of peroxide reduction and enzymatic oxidation of NADH. KW - electrochemistry KW - electron transfer KW - heme proteins KW - molecular modeling KW - monolayers Y1 - 2015 U6 - https://doi.org/10.1002/chem.201405932 SN - 0947-6539 SN - 1521-3765 VL - 21 IS - 20 SP - 7596 EP - 7602 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Kielb, Patrycja A1 - Sezer, Murat A1 - Katz, Sagie A1 - Lopez, Francesca A1 - Schulz, Christopher A1 - Gorton, Lo A1 - Ludwig, Roland A1 - Wollenberger, Ursula A1 - Zebger, Ingo A1 - Weidinger, Inez M. T1 - Spectroscopic Observation of Calcium-Induced Reorientation of Cellobiose Dehydrogenase Immobilized on Electrodes and its Effect on Electrocatalytic Activity JF - ChemPhysChem : a European journal of chemical physics and physical chemistry N2 - Cellobiose dehydrogenase catalyzes the oxidation of various carbohydrates and is considered as a possible anode catalyst in biofuel cells. It has been shown that the catalytic performance of this enzyme immobilized on electrodes can be increased by presence of calcium ions. To get insight into the Ca2+-induced changes in the immobilized enzyme we employ surface-enhanced vibrational (SERR and SEIRA) spectroscopy together with electrochemistry. Upon addition of Ca2+ ions electrochemical measurements show a shift of the catalytic turnover signal to more negative potentials while SERR measurements reveal an offset between the potential of heme reduction and catalytic current. Comparing SERR and SEIRA data we propose that binding of Ca2+ to the heme induces protein reorientation in a way that the electron transfer pathway of the catalytic FAD center to the electrode can bypass the heme cofactor, resulting in catalytic activity at more negative potentials. KW - cellobiose dehydrogenase KW - electron transfer KW - enzyme catalysis KW - spectroelectrochemistry KW - surface-enhanced vibrational spectroscopy Y1 - 2015 U6 - https://doi.org/10.1002/cphc.201500112 SN - 1439-4235 SN - 1439-7641 VL - 16 IS - 9 SP - 1960 EP - 1968 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Contin, Andrea A1 - Frasca, Stefano A1 - Vivekananthan, Jeevanthi A1 - Leimkühler, Silke A1 - Wollenberger, Ursula A1 - Plumere, Nicolas A1 - Schuhmann, Wolfgang T1 - A pH Responsive Redox Hydrogel for Electrochemical Detection of Redox Silent Biocatalytic Processes. Control of Hydrogel Solvation JF - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis N2 - The control of bioelectrocatalytic processes by external stimuli for the indirect detection of non-redox active species was achieved using an esterase and a redox enzyme both integrated within a redox hydrogel. The poly( vinyl) imidazole Os(bpy)(2)Cl hydrogel displays pH-responsive properties. The esterase catalysed reaction leads to a local pH decrease causing protonation of imidazole moieties thus increasing hydrogel solvation and mobility of the tethered Os-complexes. This is the key step to enable improved electron transfer between an aldehyde oxidoreductase and the polymer-bound Os-complexes. The off-on switch is further integrated in a biofuel cell system for self-powered signal generation. KW - pH responsive hydrogel KW - External stimuli KW - Biofuel cell KW - Self-powered biosensor KW - Solvation Y1 - 2015 U6 - https://doi.org/10.1002/elan.201400621 SN - 1040-0397 SN - 1521-4109 VL - 27 IS - 4 SP - 938 EP - 944 PB - Wiley-VCH CY - Weinheim ER -