@article{ColasEwenHannemannetal.2012, author = {Colas, Helene and Ewen, Kerstin M. and Hannemann, Frank and Bistolas, Nikitas and Wollenberger, Ursula and Bernhardt, Rita and de Oliveira, Pedro}, title = {Direct and mediated electrochemical response of the cytochrome P450 106A2 from Bacillus megaterium ATCC 13368}, series = {Bioelectrochemistry : an international journal devoted to electrochemical aspects of biology and biological aspects of electrochemistry ; official journal of the Bioelectrochemical Society}, volume = {87}, journal = {Bioelectrochemistry : an international journal devoted to electrochemical aspects of biology and biological aspects of electrochemistry ; official journal of the Bioelectrochemical Society}, number = {5}, publisher = {Elsevier}, address = {Lausanne}, issn = {1567-5394}, doi = {10.1016/j.bioelechem.2012.01.006}, pages = {71 -- 77}, year = {2012}, abstract = {CYP106A2 is one of only a few known steroid hydroxylases of bacterial origin, which might be interesting for biotechnological applications. Despite the enzyme having been studied for more than 30 years, its physiological function remains elusive. To date, there have been no reports of the redox potential of CYP106A2, which was supposed to be unusually low for a cytochrome P450. In this work we show that cyclic voltammetry is not only suitable to determine the redox potential of challenging proteins such as CYP106A2, measured at - 128 mV vs. NHE, but also to study molecular interactions of the enzyme with different interaction partners via the respective electrochemical responses. The effect of small ligands, such as carbon monoxide and cyanide, was observed on the cyclic voltammograms of CYP106A2. Furthermore, we found that Tween 80 caused a positive shift of the redox potential of immobilised CYP106A2 indicative for water expulsion from the haem environment. Moreover, electron transfer mediation phenomena with biological redox partners (e.g. ferredoxins) were studied. Finally, the influence of two different kinds of substrates on the electrochemical response of CYP106A2 was assessed, aligning observations from spectral and electrochemical studies.}, language = {en} } @article{FrascaRojasSalewskietal.2012, author = {Frasca, Stefano and Rojas, Oscar and Salewski, Johannes and Neumann, Bettina and Stiba, Konstanze and Weidinger, Inez M. and Tiersch, Brigitte and Leimk{\"u}hler, Silke and Koetz, Joachim and Wollenberger, Ursula}, title = {Human sulfite oxidase electrochemistry on gold nanoparticles modified electrode}, series = {Bioelectrochemistry : an international journal devoted to electrochemical aspects of biology and biological aspects of electrochemistry ; official journal of the Bioelectrochemical Society}, volume = {87}, journal = {Bioelectrochemistry : an international journal devoted to electrochemical aspects of biology and biological aspects of electrochemistry ; official journal of the Bioelectrochemical Society}, publisher = {Elsevier}, address = {Lausanne}, issn = {1567-5394}, doi = {10.1016/j.bioelechem.2011.11.012}, pages = {33 -- 41}, year = {2012}, abstract = {The present study reports a facile approach for sulfite biosensing, based on enhanced direct electron transfer of a human sulfite oxidase (hSO) immobilized on a gold nanoparticles modified electrode. The spherical core shell AuNPs were prepared via a new method by reduction of HAuCl4 with branched poly(ethyleneimine) in an ionic liquids resulting particles with a diameter less than 10 nm. These nanoparticles were covalently attached to a mercaptoundecanoic acid modified Au-electrode where then hSO was adsorbed and an enhanced interfacial electron transfer and electrocatalysis was achieved. UV/Vis and resonance Raman spectroscopy, in combination with direct protein voltammetry, are employed for the characterization of the system and reveal no perturbation of the structural integrity of the redox protein. The proposed biosensor exhibited a quick steady-state current response, within 2 s, a linear detection range between 0.5 and 5.4 mu M with a high sensitivity (1.85 nA mu M-1). The investigated system provides remarkable advantages in the possibility to work at low applied potential and at very high ionic strength. Therefore these properties could make the proposed system useful in the development of bioelectronic devices and its application in real samples.}, language = {en} } @article{VerganiCarminatiFerrarietal.2012, author = {Vergani, Marco and Carminati, Marco and Ferrari, Giorgio and Landini, Ettore and Caviglia, Claudia and Heiskanen, Arto and Comminges, Clement and Zor, Kinga and Sabourin, David and Dufva, Martin and Dimaki, Maria and Raiteri, Roberto and Wollenberger, Ursula and Emneus, Jenny and Sampietro, Marco}, title = {Multichannel bipotentiostat integrated with a microfluidic platform for electrochemical real-time monitoring of cell cultures}, series = {IEEE Transactions on biomedical circuits and systems}, volume = {6}, journal = {IEEE Transactions on biomedical circuits and systems}, number = {5}, publisher = {Inst. of Electr. and Electronics Engineers}, address = {Piscataway}, issn = {1932-4545}, doi = {10.1109/TBCAS.2012.2187783}, pages = {498 -- 507}, year = {2012}, abstract = {An electrochemical detection system specifically designed for multi-parameter real-time monitoring of stem cell culturing/differentiation in a microfluidic system is presented. It is composed of a very compact 24-channel electronic board, compatible with arrays of microelectrodes and coupled to a microfluidic cell culture system. A versatile data acquisition software enables performing amperometry, cyclic voltammetry and impedance spectroscopy in each of the 12 independent chambers over a 100 kHz bandwidth with current resolution down to 5 pA for 100 ms measuring time. The design of the platform, its realization and experimental characterization are reported, with emphasis on the analysis of impact of input capacitance (i.e., microelectrode size) and microfluidic pump operation on current noise. Programmable sequences of successive injections of analytes (ferricyanide and dopamine) and rinsing buffer solution as well as the impedimetric continuous tracking for seven days of the proliferation of a colony of PC12 cells are successfully demonstrated.}, language = {en} } @article{BadalyanNeumannSchaalLeimkuehleretal.2013, author = {Badalyan, Artavazd and Neumann-Schaal, Meina and Leimk{\"u}hler, Silke and Wollenberger, Ursula}, title = {A Biosensor for aromatic aldehydes comprising the mediator dependent PaoABC-Aldehyde oxidoreductase}, series = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis}, volume = {25}, journal = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis}, number = {1}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1040-0397}, doi = {10.1002/elan.201200362}, pages = {101 -- 108}, year = {2013}, abstract = {A novel aldehyde oxidoreductase (PaoABC) from Escherichia coli was utilized for the development of an oxygen insensitive biosensor for benzaldehyde. The enzyme was immobilized in polyvinyl alcohol and currents were measured for aldehyde oxidation with different one and two electron mediators with the highest sensitivity for benzaldehyde in the presence of hexacyanoferrate(III). The benzaldehyde biosensor was optimized with respect to mediator concentration, enzyme loading and pH using potassium hexacyanoferrate(III). The linear measuring range is between 0.5200 mu M benzaldehyde. In correspondence with the substrate selectivity of the enzyme in solution the biosensor revealed a preference for aromatic aldehydes and less effective conversion of aliphatic aldehydes. The biosensor is oxygen independent, which is a particularly attractive feature for application. The biosensor can be applied to detect contaminations with benzaldehyde in solvents such as benzyl alcohol, where traces of benzaldehyde in benzyl alcohol down to 0.0042?\% can be detected.}, language = {en} } @article{XuWollenbergerQianetal.2013, author = {Xu, Xuan and Wollenberger, Ursula and Qian, Jing and Lettau, Katrin and Jung, Christiane and Liu, Songqin}, title = {Electrochemically driven biocatalysis of the oxygenase domain of neuronal nitric oxide synthase in indium tin oxide nanoparticles/polyvinyl alcohol nanocomposite}, series = {Bioelectrochemistry : an international journal devoted to electrochemical aspects of biology and biological aspects of electrochemistry ; official journal of the Bioelectrochemical Society}, volume = {94}, journal = {Bioelectrochemistry : an international journal devoted to electrochemical aspects of biology and biological aspects of electrochemistry ; official journal of the Bioelectrochemical Society}, number = {47}, publisher = {Elsevier}, address = {Lausanne}, issn = {1567-5394}, doi = {10.1016/j.bioelechem.2013.04.005}, pages = {7 -- 12}, year = {2013}, abstract = {Nitric oxide synthase (NOS) plays a critical role in a number of key physiological and pathological processes. Investigation of electron-transfer reactions in NOS would contribute to a better understanding of the nitric oxide (NO) synthesis mechanism. Herein, we describe an electrochemically driven catalytic strategy, using a nanocomposite that consisted of the oxygenase domain of neuronal NOS (D290nNOSoxy), indium tin oxide (ITO) nanopartides and polyvinyl alcohol (PVA). Fast direct electron transfer between electrodes and D290nNOSoxy was observed with the heterogeneous electron transfer rate constant (k(er)) of 154.8 +/- 0.1 s(-1) at the scan rate of 5 V s(-1). Moreover, the substrate IV-hydroxy-L-arginine (NHA) was used to prove the concept of electrochemically driven biocatalysis of D290nNOSoxy. In the presence of the oxygen cosubstrate and tetrahydrobiopterin (BH4) cofactor, the addition of NHA caused the decreases of both oxidation current at + 0.1 V and reduction current at potentials ranging from -0.149 V to -0.549 V vs Ag/AgCl. Thereafter, a series of control experiments such as in the absence of BH4 or D290nNOSoxy were performed. All the results demonstrated that D290nNOSoxy biocatalysis was successfully driven by electrodes in the presence of BH4 and oxygen. This novel bioelectronic system showed potential for further investigation of NOS and biosensor applications. (C) 2013 Elsevier B.V. All rights reserved.}, language = {en} } @article{BadalyanYogaSchwuchowetal.2013, author = {Badalyan, Artavazd and Yoga, Etienne Galemou and Schwuchow, Viola and P{\"o}ller, Sascha and Schuhmann, Wolfgang and Leimk{\"u}hler, Silke and Wollenberger, Ursula}, title = {Analysis of the interaction of the molybdenum hydroxylase PaoABC from Escherichia coli with positively and negatively charged metal complexes}, series = {Electrochemistry communications : an international journal dedicated to rapid publications in electrochemistry}, volume = {37}, journal = {Electrochemistry communications : an international journal dedicated to rapid publications in electrochemistry}, publisher = {Elsevier}, address = {New York}, issn = {1388-2481}, doi = {10.1016/j.elecom.2013.09.017}, pages = {5 -- 7}, year = {2013}, abstract = {An unusual behavior of the periplasmic aldehyde oxidoreductase (PaoABC) from Escherichia coil has been observed from electrochemical investigations of the enzyme catalyzed oxidation of aromatic aldehydes with different mediators under different conditions of ionic strength. The enzyme has similarity to other molybdoenzymes of the xanthine oxidase family, but the catalytic behavior turned out to be very different. Under steady state conditions the turnover of PaoABC is maximal at pH 4 for the negatively charged ferricyanide and at pH 9 for a positively charged osmium complex. Stopped-flow kinetic measurements of the catalytic half reaction showed that oxidation of benzaldehyde proceeds also above pH 7. Thus, benzaldehyde oxidation can proceed under acidic and basic conditions using this enzyme, a property which has not been described before for molybdenum hydroxylases. It is also suggested that the electron transfer with artificial electron acceptors and PaoABC can proceed at different protein sites and depends on the nature of the electron acceptor in addition to the ionic strength. (C) 2013 Elsevier B.V. All rights reserved.}, language = {en} } @article{FrascavonGrabergFengetal.2010, author = {Frasca, Stefano and von Graberg, Till and Feng, Jiu-Ju and Thomas, Arne and Smarsly, Bernd M. and Weidinger, Inez M. and Scheller, Frieder W. and Hildebrandt, Peter and Wollenberger, Ursula}, title = {Mesoporous indium tin oxide as a novel platform for bioelectronics}, issn = {1867-3880}, doi = {10.1002/cctc.201000047}, year = {2010}, abstract = {Stable immobilization and reversible electrochemistry of cytochrome c in a tranparent indium tin oxide film with a well-defined mesoporosity (mpITO) is demonstrated. the transparency and good conductivity, in combination with the large surface area of mpITO, allow the incorporation of a high amount of elelctroactive biomolecules and their electrochemical and spectroscopic investigation. UV/Vis and resonance Raman spectroscopy, in combination with direct protein voltammetry are employed for the characterization of cytochrome c immobilized in the mpITO and reveal no perturbant of the structural of the integrity of the redox protein. The potential of this modified material as a biosensor detection of superoxide anions is also demonstrated.}, language = {en} } @article{SpricigoDronovLisdatetal.2009, author = {Spricigo, Roberto and Dronov, Roman and Lisdat, Fred and Leimk{\"u}hler, Silke and Scheller, Frieder W. and Wollenberger, Ursula}, title = {Electrocatalytic sulfite biosensor with human sulfite oxidase co-immobilized with cytochrome c in a polyelectrolyte-containing multilayer}, issn = {1618-2642}, doi = {10.1007/s00216-008-2432-y}, year = {2009}, abstract = {An efficient electrocatalytic biosensor for sulfite detection was developed by co-immobilizing sulfite oxidase and cytochrome c with polyaniline sulfonic acid in a layer-by-layer assembly. QCM, UV-Vis spectroscopy and cyclic voltammetry revealed increasing loading of electrochemically active protein with the formation of multilayers. The sensor operates reagentless at low working potential. A catalytic oxidation current was detected in the presence of sulfite at the modified gold electrode, polarized at +0.1 V ( vs. Ag/AgCl 1 M KCl). The stability of the biosensor performance was characterized and optimized. A 17-bilayer electrode has a linear range between 1 and 60 mu M sulfite with a sensitivity of 2.19 mA M-1 sulfite and a response time of 2 min. The electrode retained a stable response for 3 days with a serial reproducibility of 3.8\% and lost 20\% of sensitivity after 5 days of operation. It is possible to store the sensor in a dry state for more than 2 months. The multilayer electrode was used for determination of sulfite in unspiked and spiked samples of red and white wine. The recovery and the specificity of the signals were evaluated for each sample.}, language = {en} } @article{LoewWollenbergerSchelleretal.2009, author = {Loew, Noya and Wollenberger, Ursula and Scheller, Frieder W. and Katterle, Martin}, title = {Direct electrochemistry and spectroelectrochemistry of osmium substituted horseradish peroxidase}, issn = {1567-5394}, doi = {10.1016/j.bioelechem.2009.03.015}, year = {2009}, abstract = {In this contribution the substitution of the central protoporphyrin IX iron complex of horseradish peroxidase by the respective osmium porphyrin complex is described. The direct electrochemical reduction of the Os containing horseradish peroxidase (OsHRP) was achieved at ITO and modified glassy carbon electrodes and in combination with spectroscopy revealed the three redox couples (OsHRP)-H-III/(OsHRP)-H-IV, (OsHRP)-H-IV/(OsHRP)-H-V and (OsHRP)-H-V/ (OsHRP)-H-VI. The midpoint potentials differ dependent on the electrode material used with E-1/2 (Os-III/IV) of -0.4 V (ITO) and -0.25 V (GC), E-1/2 (Os-IV/V) of -0.16 V (ITO) and +0.10 V (GC), and E-1/2 (Os-V/VI)of +018 V (ITO), respectively Moreover, with immobilised OsHRP the direct electrocatalytic reduction of hydrogen peroxide and tert-butyl hydroperoxide was observed. In comparison to electrodes modified with native HRP the sensitivity of the OsHRP-electrode for tert-butyl hydroperoxide is higher.}, language = {en} } @article{SpricigoRichterLeimkuehleretal.2010, author = {Spricigo, Roberto and Richter, Claudia and Leimk{\"u}hler, Silke and Gorton, Lo and Scheller, Frieder W. and Wollenberger, Ursula}, title = {Sulfite biosensor based on osmium redox polymer wired sulfite oxidase}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2009.09.001}, year = {2010}, abstract = {A biosensor, based on a redoxactive osmium polymer and sulfite oxidase on screen-printed electrodes, is presented here as a promising method for the detection of sulfite. A catalytic oxidative current was generated when a sample containing sulfite was pumped over the carbon screen-printed electrode modified with osmium redox polymer wired sulfite oxidase. A stationary value was reached after approximately 50 s and a complete measurement lasted no more than 3 min. The electrode polarized at -0.1 V (vs. Ag vertical bar AgCl 1M KCl) permits minimizing the influence of interfering substances, since these compounds can be unspecific oxidized at higher potentials. Because of the good stability of the protein film on the electrode surface, a well functioning biosensor-flow system was possible to construct. The working stability and reproducibility were further enhanced by the addition of bovine serum albumin generating a more long-term stable and biocompatible protein environment. The optimized biosensor showed a stable signal for more than a week of operation and a coefficient of variation of 4.8\% for 12 successive measurements. The lower limit of detection of the sensor was 0.5 mu M sulfite and the response was linear until 100 mu M. The high sensitivity permitted a 1:500 dilution of wine samples. The immobilization procedure and the operational conditions granted minimized interferences. Additionally, repeating the immobilization procedure to form several layers of wired SO further increased the sensitivity of such a sensor. Finally. the applicability of the developed sulfite biosensor was tested on real samples, such as white and red wines.}, language = {en} }