TY - JOUR A1 - Oberländer, Jan A1 - Mayer, Marlena A1 - Greeff, Anton A1 - Keusgen, Michael A1 - Schöning, Michael Josef T1 - Spore-based biosensor to monitor the microbicidal efficacy of gaseous hydrogen peroxide sterilization processes JF - Biosensors and Bioelectronics N2 - In this work, a spore-based biosensor is evaluated to monitor the microbicidal efficacy of sterilization processes applying gaseous hydrogen peroxide (H2O2). The sensor is based on interdigitated electrode structures (IDEs) that have been fabricated by means of thin-film technologies. Impedimetric measurements are applied to study the effect of sterilization process on spores of Bacillus atrophaeus. This resilient microorganism is commonly used in industry to proof the sterilization efficiency. The sensor measurements are accompanied by conventional microbiological challenge tests, as well as morphological characterizations with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The sensor measurements are correlated with the microbiological test routines. In both methods, namely the sensor-based and microbiological one, a tailing effect has been observed. The results are evaluated and discussed in a three-dimensional calibration plot demonstrating the sensor's suitability to enable a rapid process decision in terms of a successfully performed sterilization. Y1 - 2018 U6 - http://dx.doi.org/10.1016/j.bios.2017.12.045 SN - 0956-5663 VL - 104 SP - 87 EP - 94 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Oberländer, Jan A1 - Kirchner, Patrick A1 - Keusgen, Michael A1 - Schöning, Michael Josef T1 - Strategies in developing thin-film sensors for monitoring aseptic food processes : Theoretical considerations and investigations of passivation materials JF - Electrochimica Acta N2 - The sterilization of packages in aseptic food processes is highly significant to maintain a consumer-safe product with extended shelf-life. Today, the sterilization of food packages is predominantly accomplished by gaseous hydrogen peroxide (H2O2) in combination with heat. In order to monitor this sterilization process, calorimetric gas sensors as differential set-up of two platinum temperature sensors representing a catalytically active (additionally deposition of MnO2) and a passive segment have been recently developed. The temperature rise of the exothermic decomposition serves as an indicator of the present H2O2 concentration. In the present work, a theoretical approach considering the sensor’s thermochemistry and physical transport phenomena was formulated to evaluate the temperature rise based on the energy content of gaseous H2O2. In a further part of this work, three polymers have been analyzed with respect to their application as passivation materials. The examined polymers are photoresist SU-8, perfluoroalkoxy (PFA) and fluorinated ethylene propylene (FEP). Thermal analyses by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) have been conducted to determine the operation limits of the polymers. The overall chemical resistance and stability of the polymers against the harsh environmental conditions during the sterilization process have been examined by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Y1 - 2015 U6 - http://dx.doi.org/10.1016/j.electacta.2015.06.126 SN - 0013-4686 VL - 183 SP - 130 EP - 136 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Oberländer, Jan A1 - Kirchner, Patrick A1 - Boyen, Hans-Gerd A1 - Schöning, Michael Josef T1 - Detection of hydrogen peroxide vapor by use of manganese(IV) oxide as catalyst for calorimetric gas sensors JF - Physica status solidi A: Applications and materials science N2 - In this work, the catalyst manganese(IV) oxide (MnO2), of calorimetric gas sensors (to monitor the sterilization agent vaporized hydrogen peroxide) has been investigated in more detail. Chemical analyses by means of X-ray-induced photoelectron spectroscopy have been performed to unravel the surface chemistry prior and after exposure to hydrogen peroxide vapor at elevated temperature, as applied in the sterilization processes of beverage cartons. The surface characterization reveals a change in oxidation states of the metal oxide catalyst after exposure to hydrogen peroxide. Additionally, a cleaning effect of the catalyst, which itself is attached to the sensor surface by means of a polymer interlayer, could be observed. Y1 - 2014 U6 - http://dx.doi.org/10.1002/pssa.201330359 SN - 1521-396X (E-Journal); 1862-6319 (E-Journal); 0031-8965 (Print); 1862-6300 (Print) VL - 211 IS - 6 SP - 1372 EP - 1376 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Oberländer, Jan A1 - Jildeh, Zaid B. A1 - Kirchner, Patrick A1 - Wendeler, Luisa A1 - Bromm, Alexander A1 - Iken, Heiko A1 - Wagner, Patrick A1 - Keusgen, Michael A1 - Schöning, Michael Josef T1 - Study of Interdigitated Electrode Arrays Using Experiments and Finite Element Models for the Evaluation of Sterilization Processes JF - Sensors N2 - In this work, a sensor to evaluate sterilization processes with hydrogen peroxide vapor has been characterized. Experimental, analytical and numerical methods were applied to evaluate and study the sensor behavior. The sensor set-up is based on planar interdigitated electrodes. The interdigitated electrode structure consists of 614 electrode fingers spanning over a total sensing area of 20 mm2. Sensor measurements were conducted with and without microbiological spores as well as after an industrial sterilization protocol. The measurements were verified using an analytical expression based on a first-order elliptical integral. A model based on the finite element method with periodic boundary conditions in two dimensions was developed and utilized to validate the experimental findings. Y1 - 2015 U6 - http://dx.doi.org/10.3390/s151026115 SN - 1424-8220 N1 - This article belongs to the Special Issue "Gas Sensors—Designs and Applications" VL - 15 IS - 10 SP - 26115 EP - 26127 PB - MDPI CY - Basel ER - TY - JOUR A1 - Oberländer, Jan A1 - Bromm, Alexander A1 - Wendeler, Luisa A1 - Iken, Heiko A1 - Palomar Duran, Marlena A1 - Greeff, Anton A1 - Kirchner, Patrick A1 - Keusgen, Michael A1 - Schöning, Michael Josef T1 - Towards a biosensor to monitor the sterilisation efficiency of aseptic filling machines JF - Physica status solidi (a) N2 - Sterilisation processes are compulsory in medicine, pharmacy, and food industries to prevent infections of consumers and microbiological contaminations of products. Monitoring the sterilisation by conventional microbiological methods is time- and lab-consuming. To overcome this problem, in this work a novel biosensor has been proposed. The sensor enables a fast method to evaluate sterilisation processes. By means of thin-film technology the sensor's transducer structures in form of IDEs (interdigitated electrodes) have been fabricated on a silicon substrate. Physical characterisation of the developed sensor was done by AFM, SEM, and profilometry. Impedance analyses were conducted for the electrical characterisation. As microbiological layer spores of B. atrophaeus have been immobilised on the sensing structure; spores of this type are a well-known sterilisation test organism. Impedance measurements at a fixed frequency over time were performed to monitor the immobilisation process. A sterilisation process according to aseptic filling machines was applied to demonstrate the sensor functionality. After both, immobilisation and sterilisation, a change in impedance could successfully be detected. Y1 - 2015 U6 - http://dx.doi.org/10.1002/pssa.201431900 SN - 1862-6319 VL - 212 IS - 6 SP - 1299 EP - 1305 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Näther, Niko A1 - Rolka, David A1 - Poghossian, Arshak A1 - Koudelka-Hep, M. A1 - Schöning, Michael Josef T1 - Two microcell flow-injection analysis (FIA) platforms for capacitive silicon-based field-effect sensors JF - Electrochimica Acta. 51 (2005), H. 5 Y1 - 2005 SN - 0013-4686 U6 - http://dx.doi.org/10.1016/j.electacta.2005.04.066 SP - 924 EP - 929 ER - TY - JOUR A1 - Näther, Niko A1 - Henkel, Hartmut A1 - Schneider, Andreas A1 - Schöning, Michael Josef T1 - Investigation of different catalytically active and passive materials for realising a hydrogen peroxide gas sensor JF - physica status solidi (a) . 206 (2009), H. 3 Y1 - 2009 SN - 1862-6319 N1 - Special Issue: Engineering of Functional Interfaces (EnFI 08) SP - 449 EP - 454 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Näther, Niko A1 - Emmerich, Rüdiger A1 - Berger, Jörg A1 - Friedrich, Peter A1 - Henkel, Hartmut A1 - Schneider, Andreas A1 - Schöning, Michael Josef T1 - A novel gas-phase hydrogen peroxide sensor basing on a combined physical/chemical transduction mechanism JF - Nanofunctional materials, nanostructures, and novel devices for biological and chemical detection : November 27 - December 1, 2006, Boston, Massachusetts, USA ; [at the 2006 MRS Fall Meeting]. Y1 - 2006 SN - 978-1-60423-407-7 N1 - Materials Research Society symposium proceedings ; 951 ; MRS fall meeting ; (2006.11.27-12.01 : ; Boston, Mass.) SP - 63 EP - 68 PB - Materials Research Soc. CY - Warrendale, Pa. ER - TY - JOUR A1 - Näther, Niko A1 - Berger, Jörg A1 - Emmerich, Rüdiger A1 - Friedrich, Peter A1 - Henkel, Hartmut A1 - Schneider, Andreas A1 - Schöning, Michael Josef T1 - Entwicklung einer kalorimetrischen H2O2-Gassensoranordnung für die Prozessgaskontrolle JF - 8. Dresdner Sensor-Symposium : Sensoren für Umwelt, Klima und Sicherheit, Biosensoren und Biosysteme, Sensoren und Sensorsysteme für die Prozesstechnik, Trends in der Sensortechnik, Materialentwicklung für die Sensorik; 8. Dresdner Sensor-Symposium, 10. - 12. Dezember 2007, Dresden / Gerald Gerlach ... (Hg.) Y1 - 2007 SN - 978-3-940046-45-1 N1 - Dresdner Beiträge zur Sensorik ; 29 SP - 261 EP - 264 PB - TUDpress, Verl. der Wissenschaften CY - Dresden ER - TY - JOUR A1 - Näther, Niko A1 - Berger, Jörg A1 - Emmerich, Rüdiger A1 - Friedrich, P. A1 - Henkel, H. A1 - Schöning, Michael Josef T1 - H2O2-Konzentrationsbestimmung für die Prozessgasanalytik mittels eines kalorimetrischen Sensoraufbaus JF - Sensoren und Messsysteme 2008 : 14. Fachtagung Ludwigsburg, 11. und 12. März 2008 / VDI/VDE-Gesellschaft Mess- und Automatisierungstechnik Y1 - 2008 SN - 978-3-18-092011-5 N1 - VDI-Berichte ; 2011 ; Sensoren und Messsysteme 2008, 14. GMA/ITG-Fachtagung, VDI/VDE- Gesellschaft Mess- und Automatisierungstechnik, + CD-ROM, Ludwigsburg, DE, 11.-12. Mar, 2008 SP - 783 EP - 792 PB - VDI-Verl. CY - Düsseldorf ER - TY - JOUR A1 - Näther, Niko A1 - Auger, V. A1 - Poghossian, Arshak A1 - Koudelka-Hep, M. A1 - Schöning, Michael Josef T1 - A miniaturized flow-through cell in SU-8 technique for EIS sensors JF - Biomedizinische Technik. 49 (2004), H. 2 Y1 - 2004 SN - 0932-4666 SP - 994 EP - 995 ER - TY - JOUR A1 - Muschallik, Lukas A1 - Molinnus, Denise A1 - Jablonski, Melanie A1 - Kipp, Carina Ronja A1 - Bongaerts, Johannes A1 - Pohl, Martina A1 - Wagner, Torsten A1 - Schöning, Michael Josef A1 - Selmer, Thorsten A1 - Siegert, Petra T1 - Synthesis of α-hydroxy ketones and vicinal (R, R)-diols by Bacillus clausii DSM 8716ᵀ butanediol dehydrogenase JF - RSC Advances N2 - α-hydroxy ketones (HK) and 1,2-diols are important building blocks for fine chemical synthesis. Here, we describe the R-selective 2,3-butanediol dehydrogenase from B. clausii DSM 8716ᵀ (BcBDH) that belongs to the metal-dependent medium chain dehydrogenases/reductases family (MDR) and catalyzes the selective asymmetric reduction of prochiral 1,2-diketones to the corresponding HK and, in some cases, the reduction of the same to the corresponding 1,2-diols. Aliphatic diketones, like 2,3-pentanedione, 2,3-hexanedione, 5-methyl-2,3-hexanedione, 3,4-hexanedione and 2,3-heptanedione are well transformed. In addition, surprisingly alkyl phenyl dicarbonyls, like 2-hydroxy-1-phenylpropan-1-one and phenylglyoxal are accepted, whereas their derivatives with two phenyl groups are not substrates. Supplementation of Mn²⁺ (1 mM) increases BcBDH's activity in biotransformations. Furthermore, the biocatalytic reduction of 5-methyl-2,3-hexanedione to mainly 5-methyl-3-hydroxy-2-hexanone with only small amounts of 5-methyl-2-hydroxy-3-hexanone within an enzyme membrane reactor is demonstrated. Y1 - 2020 U6 - http://dx.doi.org/10.1039/D0RA02066D SN - 2046-2069 VL - 10 SP - 12206 EP - 12216 PB - Royal Society of Chemistry (RSC) CY - Cambridge ER - TY - JOUR A1 - Muschallik, Lukas A1 - Molinnus, Denise A1 - Bongaerts, Johannes A1 - Pohl, Martina A1 - Wagner, Torsten A1 - Schöning, Michael Josef A1 - Siegert, Petra A1 - Selmer, Thorsten T1 - (R,R)-Butane-2,3-diol Dehydrogenase from Bacillus clausii DSM 8716T: Cloning and Expression of the bdhA-Gene, and Initial Characterization of Enzyme JF - Journal of Biotechnology N2 - The gene encoding a putative (R,R)-butane-2,3-diol dehydrogenase (bdhA) from Bacillus clausii DSM 8716T was isolated, sequenced and expressed in Escherichia coli. The amino acid sequence of the encoded protein is only distantly related to previously studied enzymes (identity 33–43%) and exhibited some uncharted peculiarities. An N-terminally StrepII-tagged enzyme variant was purified and initially characterized. The isolated enzyme catalyzed the (R)-specific oxidation of (R,R)- and meso-butane-2,3-diol to (R)- and (S)-acetoin with specific activities of 12 U/mg and 23 U/mg, respectively. Likewise, racemic acetoin was reduced with a specific activity of up to 115 U/mg yielding a mixture of (R,R)- and meso-butane-2,3-diol, while the enzyme reduced butane-2,3-dione (Vmax 74 U/mg) solely to (R,R)-butane-2,3-diol via (R)-acetoin. For these reactions only activity with the co-substrates NADH/NAD+ was observed. The enzyme accepted a selection of vicinal diketones, α-hydroxy ketones and vicinal diols as alternative substrates. Although the physiological function of the enzyme in B. clausii remains elusive, the data presented herein clearly demonstrates that the encoded enzyme is a genuine (R,R)-butane-2,3-diol dehydrogenase with potential for applications in biocatalysis and sensor development. Y1 - 2017 U6 - http://dx.doi.org/10.1016/j.jbiotec.2017.07.020 SN - 0168-1656 VL - 258 SP - 41 EP - 50 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Muschallik, Lukas A1 - Kipp, Carina Ronja A1 - Recker, Inga A1 - Bongaerts, Johannes A1 - Pohl, Martina A1 - Gelissen, Melanie A1 - Schöning, Michael Josef A1 - Selmer, Thorsten A1 - Siegert, Petra T1 - Synthesis of α-hydroxy ketones and vicinal diols with the Bacillus licheniformis DSM 13T butane-2, 3-diol dehydrogenase JF - Journal of Biotechnology N2 - The enantioselective synthesis of α-hydroxy ketones and vicinal diols is an intriguing field because of the broad applicability of these molecules. Although, butandiol dehydrogenases are known to play a key role in the production of 2,3-butandiol, their potential as biocatalysts is still not well studied. Here, we investigate the biocatalytic properties of the meso-butanediol dehydrogenase from Bacillus licheniformis DSM 13T (BlBDH). The encoding gene was cloned with an N-terminal StrepII-tag and recombinantly overexpressed in E. coli. BlBDH is highly active towards several non-physiological diketones and α-hydroxyketones with varying aliphatic chain lengths or even containing phenyl moieties. By adjusting the reaction parameters in biotransformations the formation of either the α-hydroxyketone intermediate or the diol can be controlled. Y1 - 2020 SN - 2590-1559 U6 - http://dx.doi.org/10.1016/j.jbiotec.2020.09.016 VL - 202 IS - Vol. 324 SP - 61 EP - 70 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Murib, Mohammed S. A1 - Tran, Anh Quang A1 - Ceuninck, Ward de A1 - Schöning, Michael Josef A1 - Nesladek, Milos A1 - Serpengüzel, Ali A1 - Wagner, Patrick T1 - Analysis of an optical biosensor based on elastic light scattering from diamond-, glass-, and sapphire microspheres JF - Physica Status Solidi A N2 - Deoxyribonucleic acid (DNA) and protein recognition are now standard tools in biology. In addition, the special optical properties of microsphere resonators expressed by the high quality factor (Q-factor) of whispering gallery modes (WGMs) or morphology dependent resonances (MDRs) have attracted the attention of the biophotonic community. Microsphere-based biosensors are considered as powerful candidates to achieve label-free recognition of single molecules due to the high sensitivity of their WGMs. When the microsphere surface is modified with biomolecules, the effective refractive index and the effective size of the microsphere change resulting in a resonant wavelength shift. The transverse electric (TE) and the transverse magnetic (TM) elastic light scattering intensity of electromagnetic waves at 600 and 1400 nm are numerically calculated for DNA and unspecific binding of proteins to the microsphere surface. The effect of changing the optical properties was studied for diamond (refractive index 2.34), glass (refractive index 1.50), and sapphire (refractive index 1.75) microspheres with a 50 µm radius. The mode spacing, the linewidth of WGMs, and the shift of resonant wavelength due to the change in radius and refractive index, were analyzed by numerical simulations. Preliminary results of unspecific binding of biomolecules are presented. The calculated shift in WGMs can be used for biomolecules detection. Y1 - 2012 U6 - http://dx.doi.org/10.1002/pssa.201100795 SN - 1862-6319 N1 - Special Issue: "Fundamentals and Applications of Diamond" VL - 209 IS - 9 SP - 1804 EP - 1810 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Murib, M. S. A1 - Yeap, W. S. A1 - Martens, D. A1 - Liu, X. A1 - Bienstman, P. A1 - Fahlman, M. A1 - Schöning, Michael Josef A1 - Michiels, L. A1 - Haenen, K. A1 - Serpengüzel, A. A1 - Wagner, Patrick T1 - Photonic studies on polymer-coated sapphire-spheres : a model system for biological ligands JF - Sensors and actuators A: Physical N2 - In this study we show an optical biosensor concept, based on elastic light scattering from sapphire microspheres. Transmitted and elastic scattering intensity of the microspheres (radius 500 μm, refractive index 1.77) on an optical fiber half coupler is analyzed at 1510 nm. The 0.43 nm angular mode spacing of the resonances is comparable to the angular mode spacing value estimated using the optical size of the microsphere. The spectral linewidths of the resonances are in the order of 0.01 nm, which corresponds to quality factors of approximately 105. A polydopamine layer is used as a functionalizing agent on sapphire microspherical resonators in view of biosensor implementation. The varying layer thickness on the microsphere is determined as a function of the resonance wavelength shift. It is shown that polymer functionalization has a minor effect on the quality factor. This is a promising step toward the development of an optical biosensor. Y1 - 2015 U6 - http://dx.doi.org/10.1016/j.sna.2014.11.024 SN - 1873-3069 (E-Journal); 0924-4247 (Print) VL - 222 SP - 212 EP - 219 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Murib, M. S. A1 - Yeap, W. S. A1 - Eurlings, Y. A1 - Grinsven, B. van A1 - Boyen, H.-G. A1 - Conings, B. A1 - Michiels, L. A1 - Ameloot, M. A1 - Carleer, R. A1 - Warmer, J. A1 - Kaul, P. A1 - Haenen, K. A1 - Schöning, Michael Josef A1 - Ceuninck, W. de A1 - Wagner, P. T1 - Heat-transfer based characterization of DNA on synthetic sapphire chips JF - Sensors and Actuators B: Chemical N2 - In this study, we show that synthetic sapphire (Al₂O₃), an established implant material, can also serve as a platform material for biosensors comparable to nanocrystalline diamond. Sapphire chips, beads, and powder were first modified with (3-aminopropyl) triethoxysilane (APTES), followed by succinic anhydride (SA), and finally single-stranded probe DNA was EDC coupled to the functionalized layer. The presence of the APTES-SA layer on sapphire powders was confirmed by thermogravimetric analyis and Fourier-transform infrared spectroscopy. Using planar sapphire chips as substrates and X-ray photoelectron spectroscopy (XPS) as surface-sensitive tool, the sequence of individual layers was analyzed with respect to their chemical state, enabling the quantification of areal densities of the involved molecular units. Fluorescence microscopy was used to demonstrate the hybridization of fluorescently tagged target DNA to the probe DNA, including denaturation- and re-hybridization experiments. Due to its high thermal conductivity, synthetic sapphire is especially suitable as a chip material for the heat-transfer method, which was employed to distinguish complementary- and non-complementary DNA duplexes containing single-nucleotide polymorphisms. These results indicate that it is possible to detect mutations electronically with a chemically resilient and electrically insulating chip material. Y1 - 2016 U6 - http://dx.doi.org/10.1016/j.snb.2016.02.027 SN - 0925-4005 VL - 230 IS - 230 SP - 260 EP - 271 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Murib, M. S. A1 - Grinsven, B. van A1 - Grieten, L. A1 - Janssens, S. D. A1 - Vermeeren, V. A1 - Eersels, K. A1 - Broeders, J. A1 - Ameloot, M. A1 - Michiels, L. A1 - Ceuninck, W. De A1 - Haenen, K. A1 - Schöning, Michael Josef A1 - Wagner, Patrick T1 - Electronic monitoring of chemical DNA denaturation on nanocrystalline diamond electrodes with different molarities and flow rates JF - Physica Status Solidi (A). Vol. 210 (2013), iss. 5 Y1 - 2013 SN - 0031-8965 SP - 911 EP - 917 PB - Wiley-VCH CY - Berlin ER - TY - JOUR A1 - Muck, A. A1 - Wang, J. A1 - Jacobs, M. A1 - Chen, G. A1 - Chatrathi, M. P. A1 - Jurka, V. A1 - Vyborny, Z. A1 - Spillmann, S. D. A1 - Sridharan, G. A1 - Schöning, Michael Josef T1 - Fabrication of poly(methyl methacrylate) microfluidic chips by atmospheric molding JF - Analytical Chemistry. 76 (2004), H. 8 Y1 - 2004 SN - 0003-2700 SP - 2290 EP - 2297 ER - TY - JOUR A1 - Mourzina, Yu.G. A1 - Schöning, Michael Josef A1 - Schubert, J. A1 - Zander, W. A1 - Legin, A. A1 - Vlasov, Y. G. A1 - Lüth, H. T1 - Thin film microsensors for fast heavy metal analysis JF - Proceedings : Copenhagen, Denmark, 27 - 30 August 2000 / [ed.: R. de Reus ...] Y1 - 2000 SN - 87-89935-50-0 N1 - Eurosensors ; (14, 2000, København) ; Eurosensors ; (14 : ; 2000.08.27-30 : ; Copenhagen) ; European Conference on Solid-State Transducers ; (14 : ; 2000.08.27-30 : ; Copenhagen) SP - 839 EP - 840 PB - MIC, Mikroelektronik Centret CY - Lyngby, Denmark ER -