@article{KeusgenJuengerKrestetal.2003, author = {Keusgen, M. and J{\"u}nger, M. and Krest, I. and Sch{\"o}ning, Michael Josef}, title = {Development of a biosensor specific for cysteine sulfoxides}, series = {Biosensors \& Bioelectronics. 18 (2003), H. 5-6}, journal = {Biosensors \& Bioelectronics. 18 (2003), H. 5-6}, isbn = {0956-5663}, pages = {805 -- 812}, year = {2003}, language = {en} } @article{PilasIkenSelmeretal.2015, author = {Pilas, Johanna and Iken, Heiko and Selmer, Thorsten and Keusgen, Michael and Sch{\"o}ning, Michael Josef}, title = {Development of a multi-parameter sensor chip for the simultaneous detection of organic compounds in biogas processes}, series = {Physica status solidi (a)}, volume = {212}, journal = {Physica status solidi (a)}, number = {6}, publisher = {Wiley}, address = {Weinheim}, issn = {1862-6319}, doi = {10.1002/pssa.201431894}, pages = {1306 -- 1312}, year = {2015}, abstract = {An enzyme-based multi-parameter biosensor is developed for monitoring the concentration of formate, d-lactate, and l-lactate in biological samples. The sensor is based on the specific dehydrogenation by an oxidized β-nicotinamide adenine dinucleotide (NAD+)-dependent dehydrogenase (formate dehydrogenase, d-lactic dehydrogenase, and l-lactic dehydrogenase, respectively) in combination with a diaphorase from Clostridium kluyveri (EC 1.8.1.4). The enzymes are immobilized on a platinum working electrode by cross-linking with glutaraldehyde (GA). The principle of the determination scheme in case of l-lactate is as follows: l-lactic dehydrogenase (l-LDH) converts l-lactate into pyruvate by reaction with NAD+. In the presence of hexacyanoferrate(III), the resulting reduced β-nicotinamide adenine dinucleotide (NADH) is then regenerated enzymatically by diaphorase. The electrochemical detection is based on the current generated by oxidation of hexacyanoferrate(II) at an applied potential of +0.3 V vs. an Ag/AgCl reference electrode. The biosensor will be electrochemically characterized in terms of linear working range and sensitivity. Additionally, the successful practical application of the sensor is demonstrated in an extract from maize silage.}, language = {en} } @article{KeusgenKloockKnobbeetal.2004, author = {Keusgen, M. and Kloock, Joachim P. and Knobbe, D.-T. and J{\"u}nger, M. and Krest, I. and Goldbach, M. and Klein, W. and Sch{\"o}ning, Michael Josef}, title = {Direct determination of cyanides by potentiometric biosensors}, series = {Sensors and Actuators B. 103 (2004), H. 1-2}, journal = {Sensors and Actuators B. 103 (2004), H. 1-2}, isbn = {0925-4005}, pages = {380 -- 385}, year = {2004}, language = {en} } @article{SchoeningKloockKnobbeetal.2004, author = {Sch{\"o}ning, Michael Josef and Kloock, Joachim P. and Knobbe, D.-T. and Krause, R. and Block, K. and Wang, J. and Mulchandani, A. and Keusgen, M.}, title = {Direktnachweis von Pestiziden und Cyanid mit elektrochemischen Enzymsensoren}, series = {Sensoren und Messsysteme 2004 : Tagung Ludwigsburg, 15. und 16. M{\"a}rz 2004 / VDI-VDE-Gesellschaft Mess- und Automatisierungstechnik}, journal = {Sensoren und Messsysteme 2004 : Tagung Ludwigsburg, 15. und 16. M{\"a}rz 2004 / VDI-VDE-Gesellschaft Mess- und Automatisierungstechnik}, publisher = {VDI}, address = {D{\"u}sseldorf}, isbn = {3-18-091829-2}, pages = {699 -- 706}, year = {2004}, language = {en} } @article{BronderPoghossianSchejaetal.2015, author = {Bronder, Thomas and Poghossian, Arshak and Scheja, Sabrina and Wu, Chunsheng and Keusgen, Michael and Mewes, Dieter and Sch{\"o}ning, Michael Josef}, title = {DNA Immobilization and Hybridization Detection by the Intrinsic Molecular Charge Using Capacitive Field-Effect Sensors Modified with a Charged Weak Polyelectrolyte Layer}, series = {Applied Materials \& Interfaces}, volume = {36}, journal = {Applied Materials \& Interfaces}, number = {7}, publisher = {American Chemical Society}, address = {Washington, DC}, doi = {10.1021/acsami.5b05146}, pages = {20068 -- 20075}, year = {2015}, abstract = {Miniaturized setup, compatibility with advanced micro- and nanotechnologies, and ability to detect biomolecules by their intrinsic molecular charge favor the semiconductor field-effect platform as one of the most attractive approaches for the development of label-free DNA chips. In this work, a capacitive field-effect EIS (electrolyte-insulator-semiconductor) sensor covered with a layer-by-layer prepared, positively charged weak polyelectrolyte layer of PAH (poly(allylamine hydrochloride)) was used for the label-free electrical detection of DNA (deoxyribonucleic acid) immobilization and hybridization. The negatively charged probe single-stranded DNA (ssDNA) molecules were electrostatically adsorbed onto the positively charged PAH layer, resulting in a preferentially flat orientation of the ssDNA molecules within the Debye length, thus yielding a reduced charge-screening effect and a higher sensor signal. Each sensor-surface modification step (PAH adsorption, probe ssDNA immobilization, hybridization with complementary target DNA (cDNA), reducing an unspecific adsorption by a blocking agent, incubation with noncomplementary DNA (ncDNA) solution) was monitored by means of capacitance-voltage and constant-capacitance measurements. In addition, the surface morphology of the PAH layer was studied by atomic force microscopy and contact-angle measurements. High hybridization signals of 34 and 43 mV were recorded in low-ionic strength solutions of 10 and 1 mM, respectively. In contrast, a small signal of 4 mV was recorded in the case of unspecific adsorption of fully mismatched ncDNA. The density of probe ssDNA and dsDNA molecules as well as the hybridization efficiency was estimated using the experimentally measured DNA immobilization and hybridization signals and a simplified double-layer capacitor model. The results of field-effect experiments were supported by fluorescence measurements, verifying the DNA-immobilization and hybridization event.}, language = {en} } @article{ArreolaKeusgenSchoening2017, author = {Arreola, Julio and Keusgen, Michael and Sch{\"o}ning, Michael Josef}, title = {Effect of O2 plasma on properties of electrolyte-insulator-semiconductor structures}, series = {physica status solidi a : applications and materials sciences}, volume = {214}, journal = {physica status solidi a : applications and materials sciences}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1862-6319}, doi = {10.1002/pssa.201700025}, pages = {Artikel 1700025}, year = {2017}, abstract = {Prior to immobilization of biomolecules or cells onto biosensor surfaces, the surface must be physically or chemically activated for further functionalization. Organosilanes are a versatile option as they facilitate the immobilization through their terminal groups and also display self-assembly. Incorporating hydroxyl groups is one of the important methods for primary immobilization. This can be done, for example, with oxygen plasma treatment. However, this treatment can affect the performance of the biosensors and this effect is not quite well understood for surface functionalization. In this work, the effect of O2 plasma treatment on EIS sensors was investigated by means of electrochemical characterizations: capacitance-voltage (C-V) and constant capacitance (ConCap) measurements. After O2 plasma treatment, the potential of the EIS sensor dramatically shifts to a more negative value. This was successfully reset by using an annealing process.}, language = {en} } @article{BronderPoghossianSchejaetal.2015, author = {Bronder, Thomas and Poghossian, Arshak and Scheja, S. and Wu, Chunsheng and Keusgen, M. and Sch{\"o}ning, Michael Josef}, title = {Electrostatic Detection of Unlabelled Single- and Double-stranded DNA Using Capacitive Field-effect Devices Functionalized with a Positively Charged Polyelectrolyte Layer}, series = {Procedia Engineering}, volume = {120}, journal = {Procedia Engineering}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1877-7058}, doi = {10.1016/j.proeng.2015.08.710}, pages = {544 -- 547}, year = {2015}, abstract = {Capacitive field-effect electrolyte-insulator-semiconductor sensors consisting of an Al-p-Si-SiO2 structure have been used for the electrical detection of unlabelled single- and double-stranded DNA (dsDNA) molecules by their intrinsic charge. A simple functionalization protocol based on the layer-by-layer (LbL) technique was used to prepare a weak polyelectrolyte/probe-DNA bilayer, followed by the hybridization with complementary target DNA molecules. Due to the flat orientation of the LbL-adsorbed DNA molecules, a high sensor signal has been achieved. In addition, direct label-free detection of in-solution hybridized dsDNA molecules has been studied.}, language = {en} } @article{KeusgenJuengerKnobbeetal.2003, author = {Keusgen, M. and J{\"u}nger, M. and Knobbe, D.-T. and Kloock, Joachim P. and Sch{\"o}ning, Michael Josef}, title = {Entwicklung eines potentiometrischen Cyanid-Biosensors auf der Basis von EIS-Strukturen}, series = {Sensoren f{\"u}r zuk{\"u}nftige Hochtechnologien und Neuentwicklungen f{\"u}r die Verfahrenstechnik / 6. Dresdner Sensor-Symposium, 8. - 10. Dezember 2003, Dresden. J{\"o}rg Peter Baselt; Gerald Gerlach (Hg.)}, journal = {Sensoren f{\"u}r zuk{\"u}nftige Hochtechnologien und Neuentwicklungen f{\"u}r die Verfahrenstechnik / 6. Dresdner Sensor-Symposium, 8. - 10. Dezember 2003, Dresden. J{\"o}rg Peter Baselt; Gerald Gerlach (Hg.)}, publisher = {w.e.b.-Univ.-Verl.}, address = {Dresden}, isbn = {3-935712-92-8}, pages = {235 -- 238}, year = {2003}, language = {de} } @article{TurekKeusgenPoghossianetal.2008, author = {Turek, M. and Keusgen, M. and Poghossian, Arshak and Mulchandani, A. and Wang, J. and Sch{\"o}ning, Michael Josef}, title = {Enzyme-modified electrolyte-insulator-semiconductor sensors}, series = {Journal of Contemporary Physics. 43 (2008), H. 2}, journal = {Journal of Contemporary Physics. 43 (2008), H. 2}, isbn = {1934-9378}, pages = {82 -- 85}, year = {2008}, language = {en} } @article{JildehOberlaenderKirchneretal.2018, author = {Jildeh, Zaid B. and Oberl{\"a}nder, Jan and Kirchner, Patrick and Keusgen, Michael and Wagner, Patrick H. and Sch{\"o}ning, Michael Josef}, title = {Experimental and Numerical Analyzes of a Sensor Based on Interdigitated Electrodes for Studying Microbiological Alterations}, series = {physica status solidi (a): applications and materials science}, volume = {215}, journal = {physica status solidi (a): applications and materials science}, number = {15}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1862-6319}, doi = {10.1002/pssa.201700920}, pages = {Artikel 1700920}, year = {2018}, abstract = {In this work, a cell-based biosensor to evaluate the sterilization efficacy of hydrogen peroxide vapor sterilization processes is characterized. The transducer of the biosensor is based on interdigitated gold electrodes fabricated on an inert glass substrate. Impedance spectroscopy is applied to evaluate the sensor behavior and the alteration of test microorganisms due to the sterilization process. These alterations are related to changes in relative permittivity and electrical conductivity of the bacterial spores. Sensor measurements are conducted with and without bacterial spores (Bacillus atrophaeus), as well as after an industrial sterilization protocol. Equivalent two-dimensional numerical models based on finite element method of the periodic finger structures of the interdigitated gold electrodes are designed and validated using COMSOL® Multiphysics software by the application of known dielectric properties. The validated models are used to compute the electrical properties at different sensor states (blank, loaded with spores, and after sterilization). As a final result, we will derive and tabulate the frequency-dependent electrical parameters of the spore layer using a novel model that combines experimental data with numerical optimization techniques.}, language = {en} }