TY - JOUR A1 - Poghossian, Arshak A1 - Abouzar, Maryam H. A1 - Christiaens, P. A1 - Williams, O. A. A1 - Haenen, K. A1 - Wagner, P. A1 - Schöning, Michael Josef T1 - Nanocrystalline diamond-based field-effect (bio-)chemical sensor 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 Sensor-Symposium <8, 2007, Dresden> ; Dresdner Beiträge zur Sensorik ; 29 SP - 191 EP - 194 PB - TUDpress, Verl. der Wissenschaften CY - Dresden ER - TY - CHAP A1 - Beging, Stefan A1 - Poghossian, Arshak A1 - Mlynek, D. A1 - Hataihimakul, S. A1 - Pedraza, A. A1 - Dhawan, S. A1 - Laube, N. A1 - Kleinen, L. A1 - Baldsiefen, G. A1 - Busch, H. A1 - Schöning, Michael Josef T1 - Ion-selective sensors for the determination of the risk of urinary stone formation T2 - Micro- and Nanosystems in biochemical diagnosis : Principles and applications Y1 - 2010 SP - 74 EP - 80 CY - Warsaw ER - TY - JOUR A1 - Schusser, Sebastian A1 - Krischer, Maximillian A1 - Bäcker, Matthias A1 - Poghossian, Arshak A1 - Wagner, Patrick A1 - Schöning, Michael Josef T1 - Monitoring of the Enzymatically Catalyzed Degradation of Biodegradable Polymers by Means of Capacitive Field-Effect Sensors JF - Analytical Chemistry N2 - Designing novel or optimizing existing biodegradable polymers for biomedical applications requires numerous tests on the effect of substances on the degradation process. In the present work, polymer-modified electrolyte–insulator–semiconductor (PMEIS) sensors have been applied for monitoring an enzymatically catalyzed degradation of polymers for the first time. The thin films of biodegradable polymer poly(d,l-lactic acid) and enzyme lipase were used as a model system. During degradation, the sensors were read-out by means of impedance spectroscopy. In order to interpret the data obtained from impedance measurements, an electrical equivalent circuit model was developed. In addition, morphological investigations of the polymer surface have been performed by means of in situ atomic force microscopy. The sensor signal change, which reflects the progress of degradation, indicates an accelerated degradation in the presence of the enzyme compared to hydrolysis in neutral pH buffer media. The degradation rate increases with increasing enzyme concentration. The obtained results demonstrate the potential of PMEIS sensors as a very promising tool for in situ and real-time monitoring of degradation of polymers. Y1 - 2015 U6 - https://doi.org/10.1021/acs.analchem.5b00617 SN - 1520-6882 VL - 87 IS - 13 SP - 6607 EP - 6613 PB - ACS Publications CY - Washington, DC ER - TY - JOUR A1 - Kramer, Friederike A1 - Halamkova, Lenka A1 - Poghossian, Arshak A1 - Schöning, Michael Josef A1 - Katz, Evgeny A1 - Halamek, Jan T1 - Biocatalytic analysis of biomarkers for forensic identification of ethnicity between Caucasian and African American JF - The analyst. August 2013 Y1 - 2013 SN - 1364-5528 (E-Journal); 0003-2654 (Print) VL - Vol. 138 SP - 6251 EP - 6257 PB - Royal Society of Chemistry CY - Cambridge ER - TY - CHAP A1 - Bäcker, Matthias A1 - Schusser, Sebastian A1 - Leinhos, Marcel A1 - Poghossian, Arshak A1 - Schöning, Michael Josef T1 - Sensor system for the monitoring of degradation processes of biodegradable biopolymers T2 - Sensoren und Messsysteme 2014 ; Beiträge der 17. GMA/ITG-Fachtagung vom 3. bis 4. Juni 2014 in Nürnberg. (ITG-Fachbericht ; 250) Y1 - 2014 SN - 978-3-8007-3622-5 SP - 1 EP - 4 PB - VDE-Verl. CY - Düsseldorf ER - TY - JOUR A1 - Bäcker, Matthias A1 - Rakowski, D. A1 - Poghossian, Arshak A1 - Biselli, Manfred A1 - Wagner, Patrick A1 - Schöning, Michael Josef T1 - Chip-based amperometric enzyme sensor system for monitoring of bioprocesses by flow-injection analysis JF - Journal of Biotechnology N2 - A microfluidic chip integrating amperometric enzyme sensors for the detection of glucose, glutamate and glutamine in cell-culture fermentation processes has been developed. The enzymes glucose oxidase, glutamate oxidase and glutaminase were immobilized by means of cross-linking with glutaraldehyde on platinum thin-film electrodes integrated within a microfluidic channel. The biosensor chip was coupled to a flow-injection analysis system for electrochemical characterization of the sensors. The sensors have been characterized in terms of sensitivity, linear working range and detection limit. The sensitivity evaluated from the respective peak areas was 1.47, 3.68 and 0.28 μAs/mM for the glucose, glutamate and glutamine sensor, respectively. The calibration curves were linear up to a concentration of 20 mM glucose and glutamine and up to 10 mM for glutamate. The lower detection limit amounted to be 0.05 mM for the glucose and glutamate sensor, respectively, and 0.1 mM for the glutamine sensor. Experiments in cell-culture medium have demonstrated a good correlation between the glutamate, glutamine and glucose concentrations measured with the chip-based biosensors in a differential-mode and the commercially available instrumentation. The obtained results demonstrate the feasibility of the realized microfluidic biosensor chip for monitoring of bioprocesses. Y1 - 2013 U6 - https://doi.org/10.1016/j.jbiotec.2012.03.014 SN - 0168-1656 VL - 163 IS - 4 SP - 371 EP - 376 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Huck, Christina A1 - Poghossian, Arshak A1 - Wagner, Patrick A1 - Schöning, Michael Josef T1 - Combined amperometric/field-effect sensor for the detection of dissolved hydrogen JF - Sensors and actuators B: Chemical N2 - Real-time and reliable monitoring of the biogas process is crucial for a stable and efficient operation of biogas production in order to avoid digester breakdowns. The concentration of dissolved hydrogen (H₂) represents one of the key parameters for biogas process control. In this work, a one-chip integrated combined amperometric/field-effect sensor for monitoring the dissolved H₂ concentration has been developed for biogas applications. The combination of two different transducer principles might allow a more accurate and reliable measurement of dissolved H₂ as an early warning indicator of digester failures. The feasibility of the approach has been demonstrated by simultaneous amperometric/field-effect measurements of dissolved H₂ concentrations in electrolyte solutions. Both, the amperometric and the field-effect transducer show a linear response behaviour in the H₂ concentration range from 0.1 to 3% (v/v) with a slope of 198.4 ± 13.7 nA/% (v/v) and 14.9 ± 0.5 mV/% (v/v), respectively. Y1 - 2012 U6 - https://doi.org/10.1016/j.snb.2012.10.050 SN - 0925-4005 N1 - Part of special issue "Selected Papers from the 14th International Meeting on Chemical Sensors" VL - 187 SP - 168 EP - 173 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Poghossian, Arshak A1 - Mai, D.-T. A1 - Mourzina, Y. A1 - Schöning, Michael Josef T1 - Impedance effect of an ion-sensitive membrane: characterisation of an EMIS sensor by impedance spectroscopy, capacitance-voltage and constant-capacitance method JF - Sensors and Actuators B. 103 (2004), H. 1-2 Y1 - 2004 SN - 0925-4005 SP - 423 EP - 428 ER - TY - JOUR A1 - Schöning, Michael Josef A1 - Poghossian, Arshak T1 - Silicon-based field-effect devices with nanostructured surfaces for bio-/chemical sensing JF - Semiconductor micro- and nanoelectronics : Proceedings of the Seventh International Conference , Tsakhcadzor, Armenia July 3-5 2009 Y1 - 2009 SP - 51 EP - 53 ER - TY - JOUR A1 - Spelthahn, Heiko A1 - Poghossian, Arshak A1 - Schöning, Michael Josef T1 - Self-aligned nanogaps and nanochannels via conventional photolithography and pattern-size reduction technique JF - Electrochimica Acta. 54 (2009), H. 25 Sp. Iss. SI Y1 - 2009 SN - 0013-4686 SP - 6010 EP - 6014 ER - TY - JOUR A1 - Beging, Stefan A1 - Leinhos, Marcel A1 - Jablonski, Melanie A1 - Poghossian, Arshak A1 - Schöning, Michael Josef T1 - Studying the spatially resolved immobilisation of enzymes on a capacitive field-effect structure by means of nano-spotting JF - Physica status solidi (a) Y1 - 2015 U6 - https://doi.org/10.1002/pssa.201431891 SN - 1862-6319 VL - 212 IS - 6 SP - 1353 EP - 1358 PB - Wiley CY - Weinheim ER - TY - CHAP A1 - Poghossian, Arshak A1 - Ingebrandt, S. A1 - Platen, J. A1 - Schöning, Michael Josef T1 - Field-effect sensors with charged macromolecules – from micro towards nano aspects T2 - Biochemical Sensing Utilisation of Micro-and Nanotechnologies, Warschau, Nov. 2005 : Lecture Notes of the ICB Seminar / ed.: M. Mascini, W. Torbicz Y1 - 2006 SP - 74 EP - 81 PB - Polish Academy Sciences Press CY - Warsaw ER - TY - JOUR A1 - Poghossian, Arshak A1 - Jablonski, Melanie A1 - Koch, Claudia A1 - Bronder, Thomas A1 - Rolka, David A1 - Wege, Christina A1 - Schöning, Michael Josef T1 - Field-effect biosensor using virus particles as scaffolds for enzyme immobilization JF - Biosensors and Bioelectronics N2 - A field-effect biosensor employing tobacco mosaic virus (TMV) particles as scaffolds for enzyme immobilization is presented. Nanotubular TMV scaffolds allow a dense immobilization of precisely positioned enzymes with retained activity. To demonstrate feasibility of this new strategy, a penicillin sensor has been developed by coupling a penicillinase with virus particles as a model system. The developed field-effect penicillin biosensor consists of an Al-p-Si-SiO₂-Ta₂O₅-TMV structure and has been electrochemically characterized in buffer solutions containing different concentrations of penicillin G. In addition, the morphology of the biosensor surface with virus particles was characterized by scanning electron microscopy and atomic force microscopy methods. The sensors possessed a high penicillin sensitivity of ~ 92 mV/dec in a nearly-linear range from 0.1 mM to 10 mM, and a low detection limit of about 50 µM. The long-term stability of the penicillin biosensor was periodically tested over a time period of about one year without any significant loss of sensitivity. The biosensor has also been successfully applied for penicillin detection in bovine milk samples. Y1 - 2018 U6 - https://doi.org/10.1016/j.bios.2018.03.036 SN - 0956-5663 VL - 110 SP - 168 EP - 174 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Poghossian, Arshak A1 - Berndsen, L. A1 - Schöning, Michael Josef T1 - Chemical sensor as a physical sensor: ISFET-based flowvelocity, flow-direction and diffusion-coefficient sensor JF - Book of abstracts / ed. by J. Saneistr. Y1 - 2002 SN - 80-01-02576-4 N1 - Eurosensors ; (16, 2002, Praha) SP - 649 EP - 652 PB - Czech Technical University, Faculty of Electrical Engineering, Department of Measurement CY - Prague 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 - CHAP A1 - Poghossian, Arshak A1 - Weiland, Maryam A1 - Schöning, Michael Josef ED - Lvova, Larisa ED - Kirsanov, Dmitry ED - di Natale, Corrado ED - Legin, Audrey T1 - Nanoplate field-effect capacitors: a new transducer structure for multiparameter (bio-)chemical sensing T2 - Multisensor system for chemical analysis : materials and sensors N2 - An array of electrically isolated nanoplate field-effect silicon-on-insulator (SOI) capacitors as a new transducer structure for multiparameter (bio-)chemical sensing is presented. The proposed approach allows addressable biasing and electrical readout of multiple nanoplate field-effect capacitive (bio-)chemical sensors on the same SOI chip, as well as differential-mode measurements. The realized sensor chip has been applied for pH and penicillin concentration measurements, electrical monitoring of polyelectrolyte multilayer formation, and the label-free electrical detection of consecutive deoxyribonucleic acid (DNA) hybridization and denaturation events. Y1 - 2014 SN - 978-981-4411-15-8 ; 978-981-4411-16-5 U6 - https://doi.org/10.1201/b15491-11 SP - 333 EP - 373 PB - Jenny Stanford Publishing CY - Singapore ET - 1 ER - TY - JOUR A1 - Buniatyan, V. A1 - Huck, Christina A1 - Poghossian, Arshak A1 - Aroutiounian, V. M. A1 - Schöning, Michael Josef T1 - BaxSr1-x TiO3/pc-Si heterojunction capacitance JF - Armenian journal of physics Y1 - 2013 SN - 1829-1171 VL - 6 IS - 4 SP - 188 EP - 197 PB - National Academy of Sciences of Armenia CY - Yerevan ER - TY - JOUR A1 - Schöning, Michael Josef A1 - Poghossian, Arshak A1 - Schultze, Joachim W. T1 - Measuring seven parameters by two ISFET modules in a microcell set-up JF - Int. Journal of Computational Engineering Science. 4 (2003), H. 2 Y1 - 2003 SN - 1465-8763 SP - 257 EP - 260 ER - TY - JOUR A1 - Huck, Christina A1 - Poghossian, Arshak A1 - Bäcker, Matthias A1 - Reisert, Steffen A1 - Kramer, Friederike A1 - Begoyan, Vardges K. A1 - Buniatyan, Vahe V. A1 - Schöning, Michael Josef T1 - Multi-parameter sensing using high-k oxide of barium strontium titanate JF - Physica status solidi (a) N2 - High-k perovskite oxide of barium strontium titanate (BST) represents a very attractive multi-functional transducer material for the development of (bio-)chemical sensors. In this work, a Si-based sensor chip containing Pt interdigitated electrodes covered with a thin BST layer (485 nm) has been developed for multi-parameter chemical sensing. The chip has been applied for the contactless measurement of the electrolyte conductivity, the detection of adsorbed charged macromolecules (positively charged polyelectrolytes of polyethylenimine) and the concentration of hydrogen peroxide (H2O2) vapor. The experimental results of functional testing of individual sensors are presented. The mechanism of the BST sensitivity to charged polyelectrolytes and H2O2 vapor has been proposed and discussed. Y1 - 2015 U6 - https://doi.org/10.1002/pssa.201431911 SN - 1862-6319 VL - 212 IS - 6 SP - 1259 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Pourshahidi, Ali Mohammad A1 - Engelmann, Ulrich M. A1 - Offenhäusser, Andreas A1 - Krause, Hans-Joachim T1 - Resolving ambiguities in core size determination of magnetic nanoparticles from magnetic frequency mixing data JF - Journal of Magnetism and Magnetic Materials N2 - Frequency mixing magnetic detection (FMMD) has been widely utilized as a measurement technique in magnetic immunoassays. It can also be used for the characterization and distinction (also known as “colourization”) of different types of magnetic nanoparticles (MNPs) based on their core sizes. In a previous work, it was shown that the large particles contribute most of the FMMD signal. This leads to ambiguities in core size determination from fitting since the contribution of the small-sized particles is almost undetectable among the strong responses from the large ones. In this work, we report on how this ambiguity can be overcome by modelling the signal intensity using the Langevin model in thermodynamic equilibrium including a lognormal core size distribution fL(dc,d0,σ) fitted to experimentally measured FMMD data of immobilized MNPs. For each given median diameter d0, an ambiguous amount of best-fitting pairs of parameters distribution width σ and number of particles Np with R2 > 0.99 are extracted. By determining the samples’ total iron mass, mFe, with inductively coupled plasma optical emission spectrometry (ICP-OES), we are then able to identify the one specific best-fitting pair (σ, Np) one uniquely. With this additional externally measured parameter, we resolved the ambiguity in core size distribution and determined the parameters (d0, σ, Np) directly from FMMD measurements, allowing precise MNPs sample characterization. Y1 - 2022 U6 - https://doi.org/10.1016/j.jmmm.2022.169969 SN - 0304-8853 VL - 563 IS - In progress, Art. No. 169969 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Rabehi, Amine A1 - Garlan, Benjamin A1 - Achtsnicht, Stefan A1 - Krause, Hans-Joachim A1 - Offenhäusser, Andreas A1 - Ngo, Kieu A1 - Neveu, Sophie A1 - Graff-Dubois, Stephanie A1 - Kokabi, Hamid T1 - Magnetic detection structure for Lab-on-Chip applications based on the frequency mixing technique JF - Sensors N2 - A magnetic frequency mixing technique with a set of miniaturized planar coils was investigated for use with a completely integrated Lab-on-Chip (LoC) pathogen sensing system. The system allows the detection and quantification of superparamagnetic beads. Additionally, in terms of magnetic nanoparticle characterization ability, the system can be used for immunoassays using the beads as markers. Analytical calculations and simulations for both excitation and pick-up coils are presented; the goal was to investigate the miniaturization of simple and cost-effective planar spiral coils. Following these calculations, a Printed Circuit Board (PCB) prototype was designed, manufactured, and tested for limit of detection, linear response, and validation of theoretical concepts. Using the magnetic frequency mixing technique, a limit of detection of 15 µg/mL of 20 nm core-sized nanoparticles was achieved without any shielding. KW - Lab-on-Chip KW - magnetic sensing KW - frequency mixing KW - superparamagnetic nanoparticles KW - magnetic beads Y1 - 2018 U6 - https://doi.org/10.3390/s18061747 SN - 1424-8220 VL - 18 IS - 6 PB - MDPI CY - Basel ER - TY - JOUR A1 - Achtsnicht, Stefan A1 - Neuendorf, Christian A1 - Faßbender, Tobias A1 - Nölke, Greta A1 - Offenhäusser, Andreas A1 - Krause, Hans-Joachim A1 - Schröper, Florian T1 - Sensitive and rapid detection of cholera toxin subunit B using magnetic frequency mixing detection JF - Plos One N2 - Cholera is a life-threatening disease caused by the cholera toxin (CT) as produced by some Vibrio cholerae serogroups. In this research we present a method which directly detects the toxin’s B subunit (CTB) in drinking water. For this purpose we performed a magnetic sandwich immunoassay inside a 3D immunofiltration column. We used two different commercially available antibodies to capture CTB and for binding to superparamagnetic beads. ELISA experiments were performed to select the antibody combination. The beads act as labels for the magnetic frequency mixing detection technique. We show that the limit of detection depends on the type of magnetic beads. A nonlinear Hill curve was fitted to the calibration measurements by means of a custom-written python software. We achieved a sensitive and rapid detection of CTB within a broad concentration range from 0.2 ng/ml to more than 700 ng/ml. Y1 - 2019 U6 - https://doi.org/10.1371/journal.pone.0219356 SN - 1932-6203 VL - 14 IS - 7 PB - Plos CY - San Francisco ER - TY - JOUR A1 - Achtsnicht, Stefan A1 - Schönenborn, Kristina A1 - Offenhäusser, Andreas A1 - Krause, Hans-Joachim T1 - Measurement of the magnetophoretic velocity of different superparamagnetic beads JF - Journal of Magnetism and Magnetic Materials N2 - The movement of magnetic beads due to a magnetic field gradient is of great interest in different application fields. In this report we present a technique based on a magnetic tweezers setup to measure the velocity factor of magnetically actuated individual superparamagnetic beads in a fluidic environment. Several beads can be tracked simultaneously in order to gain and improve statistics. Furthermore we show our results for different beads with hydrodynamic diameters between 200 and 1000 nm from diverse manufacturers. These measurement data can, for example, be used to determine design parameters for a magnetic separation system, like maximum flow rate and minimum separation time, or to select suitable beads for fixed experimental requirements. KW - magnetophoretic velocity KW - superparamagnetic bead KW - magnetic tweezers KW - magnetic separation KW - magnetic actuation Y1 - 2019 U6 - https://doi.org/10.1016/j.jmmm.2018.10.066 SN - 0304-8853 VL - 477 IS - 1 SP - 244 EP - 248 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Achtsnicht, Stefan A1 - Pourshahidi, Ali Mohammad A1 - Offenhäusser, Andreas A1 - Krause, Hans-Joachim T1 - Multiplex detection of different magnetic beads using frequency scanning in magnetic frequency mixing technique JF - Sensors N2 - In modern bioanalytical methods, it is often desired to detect several targets in one sample within one measurement. Immunological methods including those that use superparamagnetic beads are an important group of techniques for these applications. The goal of this work is to investigate the feasibility of simultaneously detecting different superparamagnetic beads acting as markers using the magnetic frequency mixing technique. The frequency of the magnetic excitation field is scanned while the lower driving frequency is kept constant. Due to the particles’ nonlinear magnetization, mixing frequencies are generated. To record their amplitude and phase information, a direct digitization of the pickup-coil’s signal with subsequent Fast Fourier Transformation is performed. By synchronizing both magnetic beads using frequency scanning in magnetic frequency mixing technique magnetic fields, a stable phase information is gained. In this research, it is shown that the amplitude of the dominant mixing component is proportional to the amount of superparamagnetic beads inside a sample. Additionally, it is shown that the phase does not show this behaviour. Excitation frequency scans of different bead types were performed, showing different phases, without correlation to their diverse amplitudes. Two commercially available beads were selected and a determination of their amount in a mixture is performed as a demonstration for multiplex measurements. KW - frequency mixing magnetic detection KW - magnetic sandwich immunoassay KW - multiparametric immunoassays Y1 - 2019 U6 - https://doi.org/10.3390/s19112599 SN - 1424-8220 VL - 19 IS - 11 PB - MDPI CY - Basel ER - TY - JOUR A1 - Wendlandt, Tim A1 - Koch, Claudia A1 - Britz, Beate A1 - Liedek, Anke A1 - Schmidt, Nora A1 - Werner, Stefan A1 - Gleba, Yuri A1 - Vahidpour, Farnoosh A1 - Welden, Melanie A1 - Poghossian, Arshak A1 - Schöning, Michael Josef T1 - Facile Purification and Use of Tobamoviral Nanocarriers for Antibody-Mediated Display of a Two-Enzyme System JF - Viruses N2 - Immunosorbent turnip vein clearing virus (TVCV) particles displaying the IgG-binding domains D and E of Staphylococcus aureus protein A (PA) on every coat protein (CP) subunit (TVCVPA) were purified from plants via optimized and new protocols. The latter used polyethylene glycol (PEG) raw precipitates, from which virions were selectively re-solubilized in reverse PEG concentration gradients. This procedure improved the integrity of both TVCVPA and the wild-type subgroup 3 tobamovirus. TVCVPA could be loaded with more than 500 IgGs per virion, which mediated the immunocapture of fluorescent dyes, GFP, and active enzymes. Bi-enzyme ensembles of cooperating glucose oxidase and horseradish peroxidase were tethered together on the TVCVPA carriers via a single antibody type, with one enzyme conjugated chemically to its Fc region, and the other one bound as a target, yielding synthetic multi-enzyme complexes. In microtiter plates, the TVCVPA-displayed sugar-sensing system possessed a considerably increased reusability upon repeated testing, compared to the IgG-bound enzyme pair in the absence of the virus. A high coverage of the viral adapters was also achieved on Ta2O5 sensor chip surfaces coated with a polyelectrolyte interlayer, as a prerequisite for durable TVCVPA-assisted electrochemical biosensing via modularly IgG-assembled sensor enzymes. KW - biosensor KW - horseradish peroxidase (HRP) KW - glucose oxidase (GOx) KW - enzyme cascade KW - turnip vein clearing virus (TVCV) KW - tobacco mosaic virus (TMV) Y1 - 2023 U6 - https://doi.org/doi.org/10.3390/v15091951 SN - 1999-4915 N1 - This article belongs to the Special Issue "Tobamoviruses 2023" VL - 9 IS - 15 PB - MDPI CY - Basel ER - TY - JOUR A1 - Pourshahidi, Ali Mohammad A1 - Achtsnicht, Stefan A1 - Nambipareechee, Mrinal Murali A1 - Offenhäusser, Andreas A1 - Krause, Hans-Joachim T1 - Multiplex detection of magnetic beads using offset field dependent frequency mixing magnetic detection JF - Sensors N2 - Magnetic immunoassays employing Frequency Mixing Magnetic Detection (FMMD) have recently become increasingly popular for quantitative detection of various analytes. Simultaneous analysis of a sample for two or more targets is desirable in order to reduce the sample amount, save consumables, and save time. We show that different types of magnetic beads can be distinguished according to their frequency mixing response to a two-frequency magnetic excitation at different static magnetic offset fields. We recorded the offset field dependent FMMD response of two different particle types at frequencies ƒ₁ + n⋅ƒ₂, n = 1, 2, 3, 4 with ƒ₁ = 30.8 kHz and ƒ₂ = 63 Hz. Their signals were clearly distinguishable by the locations of the extremes and zeros of their responses. Binary mixtures of the two particle types were prepared with different mixing ratios. The mixture samples were analyzed by determining the best linear combination of the two pure constituents that best resembled the measured signals of the mixtures. Using a quadratic programming algorithm, the mixing ratios could be determined with an accuracy of greater than 14%. If each particle type is functionalized with a different antibody, multiplex detection of two different analytes becomes feasible. KW - colorization KW - multiplex detection KW - frequency mixing magnetic detection KW - magnetic nanoparticles Y1 - 2021 U6 - https://doi.org/10.3390/s21175859 SN - 1424-8220 N1 - This article belongs to the Special Issue "Advanced Nanomaterial-Based Sensors for Biomedical Applications" VL - 21 IS - 17 PB - MDPI CY - Basel ER - TY - JOUR A1 - Haeger, Gerrit A1 - Bongaerts, Johannes A1 - Siegert, Petra T1 - A convenient ninhydrin assay in 96-well format for amino acid-releasing enzymes using an air-stable reagent JF - Analytical Biochemistry N2 - An improved and convenient ninhydrin assay for aminoacylase activity measurements was developed using the commercial EZ Nin™ reagent. Alternative reagents from literature were also evaluated and compared. The addition of DMSO to the reagent enhanced the solubility of Ruhemann's purple (RP). Furthermore, we found that the use of a basic, aqueous buffer enhances stability of RP. An acidic protocol for the quantification of lysine was developed by addition of glacial acetic acid. The assay allows for parallel processing in a 96-well format with measurements microtiter plates. Y1 - 2022 U6 - https://doi.org/10.1016/j.ab.2022.114819 SN - 1096-0309 IS - 624 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Yoshinobu, Tatsuo A1 - Miyamoto, Ko-ichiro A1 - Wagner, Torsten A1 - Schöning, Michael Josef T1 - Field-effect sensors combined with the scanned light pulse technique: from artificial olfactory images to chemical imaging technologies JF - Chemosensors N2 - The artificial olfactory image was proposed by Lundström et al. in 1991 as a new strategy for an electronic nose system which generated a two-dimensional mapping to be interpreted as a fingerprint of the detected gas species. The potential distribution generated by the catalytic metals integrated into a semiconductor field-effect structure was read as a photocurrent signal generated by scanning light pulses. The impact of the proposed technology spread beyond gas sensing, inspiring the development of various imaging modalities based on the light addressing of field-effect structures to obtain spatial maps of pH distribution, ions, molecules, and impedance, and these modalities have been applied in both biological and non-biological systems. These light-addressing technologies have been further developed to realize the position control of a faradaic current on the electrode surface for localized electrochemical reactions and amperometric measurements, as well as the actuation of liquids in microfluidic devices. KW - visualization KW - light-addressing technologies KW - scanned light pulse technique KW - field-effect structure KW - MOS KW - metal-oxide-semiconductor structure KW - catalytic metal KW - electronic nose KW - gas sensor KW - artificial olfactory image Y1 - 2024 U6 - https://doi.org/10.3390/chemosensors12020020 SN - 2227-9040 N1 - This article belongs to the Special Issue "An Exciting Journey of Chemical Sensors and Biosensors: A Theme Issue in Honor of Professor Ingemar Lundström" Corresponding author: Tatsuo Yoshinobu, Michael J. Schöning VL - 12 IS - 2 PB - MDPI CY - Basel ER - TY - JOUR A1 - Welden, Rene A1 - Jablonski, Melanie A1 - Wege, Christina A1 - Keusgen, Michael A1 - Wagner, Patrick Hermann A1 - Wagner, Torsten A1 - Schöning, Michael Josef T1 - Light-Addressable Actuator-Sensor Platform for Monitoring and Manipulation of pH Gradients in Microfluidics: A Case Study with the Enzyme Penicillinase JF - Biosensors N2 - The feasibility of light-addressed detection and manipulation of pH gradients inside an electrochemical microfluidic cell was studied. Local pH changes, induced by a light-addressable electrode (LAE), were detected using a light-addressable potentiometric sensor (LAPS) with different measurement modes representing an actuator-sensor system. Biosensor functionality was examined depending on locally induced pH gradients with the help of the model enzyme penicillinase, which had been immobilized in the microfluidic channel. The surface morphology of the LAE and enzyme-functionalized LAPS was studied by scanning electron microscopy. Furthermore, the penicillin sensitivity of the LAPS inside the microfluidic channel was determined with regard to the analyte’s pH influence on the enzymatic reaction rate. In a final experiment, the LAE-controlled pH inhibition of the enzyme activity was monitored by the LAPS. KW - microfluidics KW - enzyme kinetics KW - actuator-sensor system KW - light-addressable electrode KW - light-addressable potentiometric sensor Y1 - 2021 U6 - https://doi.org/10.3390/bios11060171 SN - 2079-6374 N1 - This article belongs to the Special Issue "Selected Papers from the 1st International Electronic Conference on Biosensors (IECB 2020)" VL - 11 IS - 6 PB - MDPI CY - Basel ER - TY - JOUR A1 - Bertz, Morten A1 - Molinnus, Denise A1 - Schöning, Michael Josef A1 - Homma, Takayuki T1 - Real-time monitoring of H₂O₂ sterilization on individual bacillus atrophaeus spores by optical sensing with trapping Raman spectroscopy JF - Chemosensors N2 - Hydrogen peroxide (H₂O₂), a strong oxidizer, is a commonly used sterilization agent employed during aseptic food processing and medical applications. To assess the sterilization efficiency with H₂O₂, bacterial spores are common microbial systems due to their remarkable robustness against a wide variety of decontamination strategies. Despite their widespread use, there is, however, only little information about the detailed time-resolved mechanism underlying the oxidative spore death by H₂O₂. In this work, we investigate chemical and morphological changes of individual Bacillus atrophaeus spores undergoing oxidative damage using optical sensing with trapping Raman microscopy in real-time. The time-resolved experiments reveal that spore death involves two distinct phases: (i) an initial phase dominated by the fast release of dipicolinic acid (DPA), a major spore biomarker, which indicates the rupture of the spore’s core; and (ii) the oxidation of the remaining spore material resulting in the subsequent fragmentation of the spores’ coat. Simultaneous observation of the spore morphology by optical microscopy corroborates these mechanisms. The dependence of the onset of DPA release and the time constant of spore fragmentation on H₂O₂ shows that the formation of reactive oxygen species from H₂O₂ is the rate-limiting factor of oxidative spore death. KW - DPA (dipicolinic acid) KW - sterilization KW - Bacillus atrophaeus spores KW - optical trapping KW - Raman spectroscopy KW - optical sensor setup Y1 - 2023 U6 - https://doi.org/10.3390/chemosensors11080445 SN - 2227-9040 N1 - This article belongs to the Special Issue "Biosensors and Chemical Sensors for Food and Healthcare Monitoring—Celebrating the 10th Anniversary" VL - 8 IS - 11 PB - MDPI CY - Basel ER - TY - CHAP A1 - Moreno, Lia A1 - Dosev, D. A1 - Bratov, A. A1 - Dominguez, C. A1 - Schöning, Michael Josef A1 - Kloock, Joachim P. T1 - Effect of electrical properties of the surrounding medium on the response of an interdigitated electrode array with chalcogenide glass film T2 - XX Eurosensors : 20th anniversary ; Göteborg, Sweden, 17 - 20 September 2006 ; [proceedings]. - Vol. 1 Y1 - 2006 SN - 978-91-631-9280-7 N1 - Paper number: T1A-P22 SP - 384 EP - 385 CY - Göteborg ER - TY - JOUR A1 - Engelmann, Ulrich M. A1 - Simsek, Beril A1 - Shalaby, Ahmed A1 - Krause, Hans-Joachim T1 - Key contributors to signal generation in frequency mixing magnetic detection (FMMD): an in silico study JF - Sensors N2 - Frequency mixing magnetic detection (FMMD) is a sensitive and selective technique to detect magnetic nanoparticles (MNPs) serving as probes for binding biological targets. Its principle relies on the nonlinear magnetic relaxation dynamics of a particle ensemble interacting with a dual frequency external magnetic field. In order to increase its sensitivity, lower its limit of detection and overall improve its applicability in biosensing, matching combinations of external field parameters and internal particle properties are being sought to advance FMMD. In this study, we systematically probe the aforementioned interaction with coupled Néel–Brownian dynamic relaxation simulations to examine how key MNP properties as well as applied field parameters affect the frequency mixing signal generation. It is found that the core size of MNPs dominates their nonlinear magnetic response, with the strongest contributions from the largest particles. The drive field amplitude dominates the shape of the field-dependent response, whereas effective anisotropy and hydrodynamic size of the particles only weakly influence the signal generation in FMMD. For tailoring the MNP properties and parameters of the setup towards optimal FMMD signal generation, our findings suggest choosing large particles of core sizes dc > 25 nm nm with narrow size distributions (σ < 0.1) to minimize the required drive field amplitude. This allows potential improvements of FMMD as a stand-alone application, as well as advances in magnetic particle imaging, hyperthermia and magnetic immunoassays. KW - key performance indicators KW - magnetic biosensing KW - coupled Néel–Brownian relaxation dynamics KW - frequency mixing magnetic detection KW - magnetic relaxation KW - micromagnetic simulation KW - magnetic nanoparticles Y1 - 2024 U6 - https://doi.org/10.3390/s24061945 SN - 1424-8220 N1 - This article belongs to the Special Issue "Advances in Magnetic Sensors and Their Applications" VL - 24 IS - 6 PB - MDPI CY - Basel ER - TY - JOUR A1 - Vahidpour, Farnoosh A1 - Alghazali, Yousef A1 - Akca, Sevilay A1 - Hommes, Gregor A1 - Schöning, Michael Josef T1 - An Enzyme-Based Interdigitated Electrode-Type Biosensor for Detecting Low Concentrations of H₂O₂ Vapor/Aerosol JF - Chemosensors N2 - This work introduces a novel method for the detection of H₂O₂ vapor/aerosol of low concentrations, which is mainly applied in the sterilization of equipment in medical industry. Interdigitated electrode (IDE) structures have been fabricated by means of microfabrication techniques. A differential setup of IDEs was prepared, containing an active sensor element (active IDE) and a passive sensor element (passive IDE), where the former was immobilized with an enzymatic membrane of horseradish peroxidase that is selective towards H₂O₂. Changes in the IDEs’ capacitance values (active sensor element versus passive sensor element) under H₂O₂ vapor/aerosol atmosphere proved the detection in the concentration range up to 630 ppm with a fast response time (<60 s). The influence of relative humidity was also tested with regard to the sensor signal, showing no cross-sensitivity. The repeatability assessment of the IDE biosensors confirmed their stable capacitive signal in eight subsequent cycles of exposure to H₂O₂ vapor/aerosol. Room-temperature detection of H₂O₂ vapor/aerosol with such miniaturized biosensors will allow a future three-dimensional, flexible mapping of aseptic chambers and help to evaluate sterilization assurance in medical industry. Y1 - 2022 U6 - https://doi.org/10.3390/chemosensors10060202 SN - 2227-9040 N1 - This article belongs to the Special Issue "Bioinspired Chemical Sensors and Micro-Nano Devices" VL - 10 IS - 6 PB - MDPI CY - Basel ER -