@article{YarmanSchulzSygmundetal.2014, author = {Yarman, Aysu and Schulz, Christopher and Sygmund, Cristoph and Ludwig, Roland and Gorton, Lo and Wollenberger, Ursula and Scheller, Frieder W.}, title = {Third generation ATP sensor with enzymatic analyte recycling}, series = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis}, volume = {26}, journal = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis}, number = {9}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1040-0397}, doi = {10.1002/elan.201400231}, pages = {2043 -- 2048}, year = {2014}, abstract = {For the first time the direct electron transfer of an enzyme - cellobiose dehydrogenase, CDH - has been coupled with the hexokinase catalyzed competition for glucose in a sensor for ATP. To enhance the signal output for ATP, pyruvate kinase was coimmobilized to recycle ADP by the phosphoenolpyruvate driven reaction. The new sensor overcomes the limit of 1:1 stoichiometry of the sequential or competitive conversion of ATP by effective enzymatic recycling of the analyte. The anodic oxidation of the glucose converting CDH proceeds at electrode potentials below 0 mV vs. Ag vertical bar AgCl thus potentially interfering substances like ascorbic acid or catecholamines do not influence the measuring signal. The combination of direct electron transfer of CDH with the enzymatic recycling results in an interference-free and oxygen-independent measurement of ATP in the lower mu molar concentration range with a lower limit of detection of 63.3 nM (S/N=3).}, language = {en} } @article{ZorHeiskanenCavigliaetal.2014, author = {Zor, K. and Heiskanen, A. and Caviglia, Claudia and Vergani, M. and Landini, E. and Shah, F. and Carminati, Marco and Martinez-Serrano, A. and Ramos Moreno, T. and Kokaia, M. and Benayahu, Dafna and Keresztes, Zs. and Papkovsky, D. and Wollenberger, Ursula and Svendsen, W. E. and Dimaki, M. and Ferrari, G. and Raiteri, R. and Sampietro, M. and Dufva, M. and Emneus, Jenny}, title = {A compact multifunctional microfluidic platform for exploring cellular dynamics in real-time using electrochemical detection}, series = {RSC Advances}, volume = {4}, journal = {RSC Advances}, number = {109}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c4ra12632g}, pages = {63761 -- 63771}, year = {2014}, abstract = {Downscaling of microfluidic cell culture and detection devices for electrochemical monitoring has mostly focused on miniaturization of the microfluidic chips which are often designed for specific applications and therefore lack functional flexibility. We present a compact microfluidic cell culture and electrochemical analysis platform with in-built fluid handling and detection, enabling complete cell based assays comprising on-line electrode cleaning, sterilization, surface functionalization, cell seeding, cultivation and electrochemical real-time monitoring of cellular dynamics. To demonstrate the versatility and multifunctionality of the platform, we explored amperometric monitoring of intracellular redox activity in yeast (Saccharomyces cerevisiae) and detection of exocytotically released dopamine from rat pheochromocytoma cells (PC12). Electrochemical impedance spectroscopy was used in both applications for monitoring cell sedimentation and adhesion as well as proliferation in the case of PC12 cells. The influence of flow rate on the signal amplitude in the detection of redox metabolism as well as the effect of mechanical stimulation on dopamine release were demonstrated using the programmable fluid handling capability. The here presented platform is aimed at applications utilizing cell based assays, ranging from e.g. monitoring of drug effects in pharmacological studies, characterization of neural stem cell differentiation, and screening of genetically modified microorganisms to environmental monitoring.}, 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{DeyAdamovskiFriebeetal.2014, author = {Dey, Pradip and Adamovski, Miriam and Friebe, Simon and Badalyan, Artavazd and Mutihac, Radu-Cristian and Paulus, Florian and Leimk{\"u}hler, Silke and Wollenberger, Ursula and Haag, Rainer}, title = {Dendritic polyglycerol-poly(ethylene glycol)-based polymer networks for biosensing application}, series = {ACS applied materials \& interfaces}, volume = {6}, journal = {ACS applied materials \& interfaces}, number = {12}, publisher = {American Chemical Society}, address = {Washington}, issn = {1944-8244}, doi = {10.1021/am502018x}, pages = {8937 -- 8941}, year = {2014}, abstract = {This work describes the formation of a new dendritic polyglycerol-poly(ethylene glycol)-based 3D polymer network as a matrix for immobilization of the redox enzyme periplasmatic aldehyde oxidoreductase to create an electrochemical biosensor. The novel network is built directly on the gold surface, where it simultaneously stabilizes the enzyme for up to 4 days. The prepared biosensors can be used for amperometric detection of benzaldehyde in the range of 0.8-400 mu M.}, language = {en} } @article{NeumannYarmanWollenbergeretal.2014, author = {Neumann, Bettina and Yarman, Aysu and Wollenberger, Ursula and Scheller, Frieder W.}, title = {Characterization of the enhanced peroxidatic activity of amyloid beta peptide-hemin complexes towards neurotransmitters}, series = {Analytical \& bioanalytical chemistry}, volume = {406}, journal = {Analytical \& bioanalytical chemistry}, number = {14}, publisher = {Springer}, address = {Heidelberg}, issn = {1618-2642}, doi = {10.1007/s00216-014-7822-8}, pages = {3359 -- 3364}, year = {2014}, abstract = {Binding of heme to the amyloid peptides A beta 40/42 is thought to be an initial step in the development of symptoms in the early stages of Alzheimer's disease by enhancing the intrinsic peroxidatic activity of heme. We found considerably higher acceleration of the reaction for the physiologically relevant neurotransmitters dopamine and serotonin than reported earlier for the artificial substrate 3,3',5,5'-tetramethylbenzidine (TMB). Thus, the binding of hemin to A beta peptides might play an even more crucial role in the early stages of Alzheimer's disease than deduced from these earlier results. To mimic complex formation, a new surface architecture has been developed: The interaction between the truncated amyloid peptide A beta 1-16 and hemin immobilized on an aminohexanethiol spacer on a gold electrode has been analyzed by cyclic voltammetry. The resulting complex has a redox pair with a 25 mV more cathodic formal potential than hemin alone.}, language = {en} } @article{SchellerYarmanBachmannetal.2014, author = {Scheller, Frieder W. and Yarman, Aysu and Bachmann, Till and Hirsch, Thomas and Kubick, Stefan and Renneberg, Reinhard and Schumacher, Soeren and Wollenberger, Ursula and Teller, Carsten and Bier, Frank Fabian}, title = {Future of biosensors: a personal view}, series = {Advances in biochemical engineering, biotechnology}, volume = {140}, journal = {Advances in biochemical engineering, biotechnology}, editor = {Gu, MB and Kim, HS}, publisher = {Springer}, address = {Berlin}, isbn = {978-3-642-54143-8; 978-3-642-54142-1}, issn = {0724-6145}, doi = {10.1007/10_2013_251}, pages = {1 -- 28}, year = {2014}, abstract = {Biosensors representing the technological counterpart of living senses have found routine application in amperometric enzyme electrodes for decentralized blood glucose measurement, interaction analysis by surface plasmon resonance in drug development, and to some extent DNA chips for expression analysis and enzyme polymorphisms. These technologies have already reached a highly advanced level and need minor improvement at most. The dream of the "100-dollar' personal genome may come true in the next few years provided that the technological hurdles of nanopore technology or of polymerase-based single molecule sequencing can be overcome. Tailor-made recognition elements for biosensors including membrane-bound enzymes and receptors will be prepared by cell-free protein synthesis. As alternatives for biological recognition elements, molecularly imprinted polymers (MIPs) have been created. They have the potential to substitute antibodies in biosensors and biochips for the measurement of low-molecular-weight substances, proteins, viruses, and living cells. They are more stable than proteins and can be produced in large amounts by chemical synthesis. Integration of nanomaterials, especially of graphene, could lead to new miniaturized biosensors with high sensitivity and ultrafast response. In the future individual therapy will include genetic profiling of isoenzymes and polymorphic forms of drug-metabolizing enzymes especially of the cytochrome P450 family. For defining the pharmacokinetics including the clearance of a given genotype enzyme electrodes will be a useful tool. For decentralized online patient control or the integration into everyday "consumables' such as drinking water, foods, hygienic articles, clothing, or for control of air conditioners in buildings and cars and swimming pools, a new generation of "autonomous' biosensors will emerge.}, language = {en} } @misc{ZorHeiskanenCavigliaetal.2014, author = {Z{\´o}r, K. and Heiskanen, A. and Caviglia, Claudia and Vergani, M. and Landini, E. and Shah, F. and Carminati, Marco and Mart{\´i}nez-Serrano, A. and Ramos Moreno, T. and Kokaia, M. and Benayahu, Dafna and Keresztes, Zs. and Papkovsky, D. and Wollenberger, Ursula and Svendsen, W. E. and Dimaki, M. and Ferrari, G. and Raiteri, R. and Sampietro, M. and Dufva, M. and Emn{\´e}us, J.}, title = {A compact multifunctional microfluidic platform for exploring cellular dynamics in real-time using electrochemical detection}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-99492}, pages = {11}, year = {2014}, abstract = {Downscaling of microfluidic cell culture and detection devices for electrochemical monitoring has mostly focused on miniaturization of the microfluidic chips which are often designed for specific applications and therefore lack functional flexibility. We present a compact microfluidic cell culture and electrochemical analysis platform with in-built fluid handling and detection, enabling complete cell based assays comprising on-line electrode cleaning, sterilization, surface functionalization, cell seeding, cultivation and electrochemical real-time monitoring of cellular dynamics. To demonstrate the versatility and multifunctionality of the platform, we explored amperometric monitoring of intracellular redox activity in yeast (Saccharomyces cerevisiae) and detection of exocytotically released dopamine from rat pheochromocytoma cells (PC12). Electrochemical impedance spectroscopy was used in both applications for monitoring cell sedimentation and adhesion as well as proliferation in the case of PC12 cells. The influence of flow rate on the signal amplitude in the detection of redox metabolism as well as the effect of mechanical stimulation on dopamine release were demonstrated using the programmable fluid handling capability. The here presented platform is aimed at applications utilizing cell based assays, ranging from e.g. monitoring of drug effects in pharmacological studies, characterization of neural stem cell differentiation, and screening of genetically modified microorganisms to environmental monitoring.}, language = {en} } @misc{CommingesFrascaSuetterlinetal.2014, author = {Comminges, Cl{\´e}ment and Frasca, Stefano and S{\"u}tterlin, Martin and Wischerhoff, Erik and Laschewsky, Andr{\´e} and Wollenberger, Ursula}, title = {Surface modification with thermoresponsive polymer brushes for a switchable electrochemical sensor}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-99471}, 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} }