@article{ZengFrascaRumschoetteletal.2016, author = {Zeng, Ting and Frasca, Stefano and Rumsch{\"o}ttel, Jens and Koetz, Joachim and Leimk{\"u}hler, Silke and Wollenberger, Ursula}, title = {Role of Conductive Nanoparticles in the Direct Unmediated Bioelectrocatalysis of Immobilized Sulfite Oxidase}, series = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis}, volume = {28}, journal = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1040-0397}, doi = {10.1002/elan.201600246}, pages = {2303 -- 2310}, year = {2016}, language = {en} } @article{ContinFrascaVivekananthanetal.2015, author = {Contin, Andrea and Frasca, Stefano and Vivekananthan, Jeevanthi and Leimk{\"u}hler, Silke and Wollenberger, Ursula and Plumere, Nicolas and Schuhmann, Wolfgang}, title = {A pH Responsive Redox Hydrogel for Electrochemical Detection of Redox Silent Biocatalytic Processes. Control of Hydrogel Solvation}, series = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis}, volume = {27}, journal = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis}, number = {4}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1040-0397}, doi = {10.1002/elan.201400621}, pages = {938 -- 944}, year = {2015}, abstract = {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.}, language = {en} } @article{CommingesFrascaSuetterlinetal.2014, author = {Comminges, Clement and Frasca, Stefano and Suetterlin, Martin and Wischerhoff, Erik and Laschewsky, Andr{\´e} and Wollenberger, Ursula}, title = {Surface modification with thermoresponsive polymer brushes for a switchable electrochemical sensor}, series = {RSC Advances}, volume = {4}, journal = {RSC Advances}, number = {81}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c4ra07190e}, pages = {43092 -- 43097}, year = {2014}, abstract = {Elaboration of switchable surfaces represents an interesting way for the development of a new generation of electrochemical sensors. In this paper, a method for growing thermoresponsive polymer brushes from a gold surface pre-modified with polyethyleneimine (PEI), subsequent layer-by-layer polyelectrolyte assembly and adsorption of a charged macroinitiator is described. We propose an easy method for monitoring the coil-to-globule phase transition of the polymer brush using an electrochemical quartz crystal microbalance with dissipation (E-QCM-D). The surface of these polymer modified electrodes shows reversible switching from the swollen to the collapsed state with temperature. As demonstrated from E-QCM-D measurements using an original signal processing method, the switch is operating in three reversible steps related to different interfacial viscosities. Moreover, it is shown that the one electron oxidation of ferrocene carboxylic acid is dramatically affected by the change from the swollen to the collapsed state of the polymer brush, showing a spectacular 86\% decrease of the charge transfer resistance between the two states.}, language = {en} } @article{AksuFrascaWollenbergeretal.2011, author = {Aksu, Yilmaz and Frasca, Stefano and Wollenberger, Ursula and Driess, Matthias and Thomas, Arne}, title = {A molecular precursor approach to tunable porous tin-rich indium tin oxide with durable high electrical conductivity for bioelectronic devices}, series = {Chemistry of materials : a publication of the American Chemical Society}, volume = {23}, journal = {Chemistry of materials : a publication of the American Chemical Society}, number = {7}, publisher = {American Chemical Society}, address = {Washington}, issn = {0897-4756}, doi = {10.1021/cm103087p}, pages = {1798 -- 1804}, year = {2011}, abstract = {The preparation of porous, i.e., high surface area electrodes from transparent conducting oxides, is a valuable goal in materials chemistry as such electrodes can enable further development of optoelectronic, electrocatalytic, or bioelectronic devices. In this work the first tin-rich mesoporous indium tin oxide is prepared using the molecular heterobimetallic single-source precursor, indium tin tris-tert-butoxide, together with an appropriate structure-directing template, yielding materials with high surface areas and tailorable pore size. The resulting mesoporous tin-rich ITO films show a high and durable electrical conductivity and transparency, making them interesting materials for hosting electroactive biomolecules such as proteins. In fact, its unique performance in bioelectronic applications has been demonstrated by immobilization of high amounts of cytochrome c into the mesoporous film which undergo redox processes directly with the conductive electrode material.}, language = {en} } @article{FrascaRichtervonGrabergetal.2011, author = {Frasca, Stefano and Richter, Claudia and von Graberg, Till and Smarsly, Bernd M. and Wollenberger, Ursula}, title = {Electrochemical switchable protein-based optical device}, series = {Engineering in life sciences : Industry, Environment, Plant, Food}, volume = {11}, journal = {Engineering in life sciences : Industry, Environment, Plant, Food}, number = {6}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {1618-0240}, doi = {10.1002/elsc.201100079}, pages = {554 -- 558}, year = {2011}, abstract = {The present work contributes to the development of reusable sensing systems with a visual evaluation of the detection process related to an analyte. An electrochemical switchable protein-based optical device was designed with the core part composed of cytochrome c immobilized in a mesoporous indium tin oxide film. A color-developing redox-sensitive dye was used as switchable component of the system. The cytochrome c-catalyzed oxidation of the dye by hydrogen peroxide is spectroscopically investigated. When the dye is co-immobilized with the protein, its redox state is easily controlled by application of an electrical potential at the supporting material. This enables to electrochemically reset the system to the initial state and repetitive signal generation. The implemented reset function of the color forming reaction will make calibration of small test devices possible. The principle can be extended to other color forming redox reactions and to coupled enzyme systems, such as rapid food testing and indication of critical concentrations of metabolites for health care.}, 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{FrascaMilanGuietetal.2013, author = {Frasca, Stefano and Milan, Anabel Molero and Guiet, Amandine and Goebel, Caren and Perez-Caballero, Fernando and Stiba, Konstanze and Leimk{\"u}hler, Silke and Fischer, Anna and Wollenberger, Ursula}, title = {Bioelectrocatalysis at mesoporous antimony doped tin oxide electrodes-Electrochemical characterization and direct enzyme communication}, series = {ELECTROCHIMICA ACTA}, volume = {110}, journal = {ELECTROCHIMICA ACTA}, number = {2}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {OXFORD}, issn = {0013-4686}, doi = {10.1016/j.electacta.2013.03.144}, pages = {172 -- 180}, year = {2013}, abstract = {In this paper we report immobilization and bioelectrocatalysis of human sulfite oxidase (hSO) on nanostructured antimony doped tin oxide (ATO) thin film electrodes. Two types of ATO thin film electrodes were prepared via evaporation induced self-assembly of ATO nanoparticle sols. The use of a porogen results in different porosity and film thickness. Nevertheless both electrode types reveal similar quasi reversible electrochemical behavior for positive and negatively charged small mediators. Facile and durable immobilization of catalytically active enzyme in a direct electron transfer configuration was achieved without further chemical modification of the ATO surfaces. Interestingly, the binding of hSO onto the ATO surface seems to be not only of electrostatic nature, but also originates from a strong interaction between the histidine-tag of the enzyme and the supporting material. This is suggested from stable sulfite dependent bioelectrocatalytic signals at high ionic strength and imidazole desorption experiments. As such, ATO appears as a promising conductive platform for the immobilization of complex enzymes and their application in bioelectrocatalysis. (C) 2013 Elsevier Ltd. 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} }