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  • Schöning, Michael Josef (73)
  • Keusgen, Michael (55)
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  • acetoin (2)
  • capacitive field-effect sensor (2)
  • tobacco mosaic virus (TMV) (2)
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  • Capacitive field-effect sensor (1)
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Determination of the extracellular acidification of Escherichia coli by a light-addressable potentiometric sensor (2011)
Werner, Frederik ; Krumbe, Christoph ; Schumacher, Katharina ; Groebel, Simone ; Spelthahn, Heiko ; Stellberg, Michael ; Wagner, Torsten ; Yoshinobu, Tatsuo ; Selmer, Thorsten ; Keusgen, Michael ; Baumann, Marcus ; Schöning, Michael Josef
Detection of Adrenaline Based on Bioelectrocatalytical System to Support Tumor Diagnostic Technology (2017)
Molinnus, Denise ; Hardt, Gabriel ; Käver, Larissa ; Willenberg, Holger S. ; Poghossian, Arshak ; Keusgen, Michael ; Schöning, Michael Josef
An amperometric biosensor based on the bioelectrocatalytic measurement principle for the detection of adrenaline has been developed. The adrenaline sensor has been prepared by modification of a platinum thin-film electrode with a pyrroloquinoline quinone-dependent glucose dehydrogenase. The enzyme was immobilized via cross-linking method. Lower detection limit of 1 nM of adrenaline has been achieved by measuring at physiological level at pH 7.4.
Herstellung und Charakterisierung eines hybriden Sensorarrays auf Halbleiterbasis für die Umweltanalytik (2008)
Turek, Monika ; Schöning, Michael Josef ; Kloock, Joachim P. ; Schubert, Jürgen ; Zander, Willi ; Krüger, Peter ; Keusgen, Michael
Toward a Hybrid Biosensor System for Analysis of Organic and Volatile Fatty Acids in Fermentation Processes (2018)
Röhlen, Desiree ; Pilas, Johanna ; Dahmen, Markus ; Keusgen, Michael ; Selmer, Thorsten ; Schöning, Michael Josef
Monitoring of organic acids (OA) and volatile fatty acids (VFA) is crucial for the control of anaerobic digestion. In case of unstable process conditions, an accumulation of these intermediates occurs. In the present work, two different enzyme-based biosensor arrays are combined and presented for facile electrochemical determination of several process-relevant analytes. Each biosensor utilizes a platinum sensor chip (14 × 14 mm²) with five individual working electrodes. The OA biosensor enables simultaneous measurement of ethanol, formate, d- and l-lactate, based on a bi-enzymatic detection principle. The second VFA biosensor provides an amperometric platform for quantification of acetate and propionate, mediated by oxidation of hydrogen peroxide. The cross-sensitivity of both biosensors toward potential interferents, typically present in fermentation samples, was investigated. The potential for practical application in complex media was successfully demonstrated in spiked sludge samples collected from three different biogas plants. Thereby, the results obtained by both of the biosensors were in good agreement to the applied reference measurements by photometry and gas chromatography, respectively. The proposed hybrid biosensor system was also used for long-term monitoring of a lab-scale biogas reactor (0.01 m³) for a period of 2 months. In combination with typically monitored parameters, such as gas quality, pH and FOS/TAC (volatile organic acids/total anorganic carbonate), the amperometric measurements of OA and VFA concentration could enhance the understanding of ongoing fermentation processes.
Neue Ansteuerungselektronik für LAPS-basierte Biosensoren zur gleichzeitig ortsaufgelösten Messung der pH-Konzentration (2010)
Werner, Frederik ; Spelthahn, Heiko ; Schöning, Michael Josef ; Krumbe, Christoph ; Wagner, Torsten ; Yoshinobu, Tatsuo ; Keusgen, Michael
Ein lichtadressierbarer potentiometrischer Sensor (LAPS) kann die Konzentration eines oder mehrerer Analyten ortsaufgelöst auf der Sensoroberfläche nachweisen. Dazu wird mit einer modulierten Lichtquelle die Halbleiterstruktur des zu untersuchenden Bereiches angeregt und ein entsprechender Photostrom ausgelesen. Durch gleichzeitige Anregung mehrere Bereiche durch Lichtquellen mit unterschiedlichen Modulationsfrequenzen können diese auch zeitgleich ausgelesen werden. Mit der neuen, hier vorgestellten Ansteuerungselektronik integriert in einem "Field Programmable Gate Array" (FPGA) ist es möglich, mehrere Leuchtquellen gleichzeitig mit unterschiedlichen, während der Laufzeit festlegbaren Frequenzen, Phasen und Lichtintensitäten zu betreiben. Somit kann das Frequenzverhalten des Sensors untersucht und die Konzentration des Analyten über das Oberflächenpotential mit Hilfe von Strom/Spannungs-Kurven und Phase/Spannungs-Kurven bestimmt werden.
Capacitive field‐effect biosensor applied for the detection of acetoin in alcoholic beverages and fermentation broths (2021)
Jablonski, Melanie ; Münstermann, Felix ; Nork, Jasmina ; Molinnus, Denise ; Muschallik, Lukas ; Bongaerts, Johannes ; Wagner, Torsten ; Keusgen, Michael ; Siegert, Petra ; Schöning, Michael Josef
An acetoin biosensor based on a capacitive electrolyte–insulator–semiconductor (EIS) structure modified with the enzyme acetoin reductase, also known as butane-2,3-diol dehydrogenase (Bacillus clausii DSM 8716ᵀ), is applied for acetoin detection in beer, red wine, and fermentation broth samples for the first time. The EIS sensor consists of an Al/p-Si/SiO₂/Ta₂O₅ layer structure with immobilized acetoin reductase on top of the Ta₂O₅ transducer layer by means of crosslinking via glutaraldehyde. The unmodified and enzyme-modified sensors are electrochemically characterized by means of leakage current, capacitance–voltage, and constant capacitance methods, respectively.
Concept for a biomolecular logic chip with an integrated sensor and actuator function (2015)
Molinnus, Denise ; Bäcker, Matthias ; Iken, Heiko ; Poghossian, Arshak ; Keusgen, Michael ; Schöning, Michael Josef
A concept for a new generation of an integrated multi-functional biosensor/actuator system is developed, which is based on biomolecular logic principles. Such a system is expected to be able to detect multiple biochemical input signals simultaneously and in real-time and convert them into electrical output signals with logical operations such as OR, AND, etc. The system can be designed as a closed-loop drug release device triggered by an enzyme logic gate, while the release of the drug induced by the actuator at the required dosage and timing will be controlled by an additional drug sensor. Thus, the system could help to make an accurate and specific diagnosis. The presented concept is exemplarily demonstrated by using an enzyme logic gate based on a glucose/glucose oxidase system, a temperature-responsive hydrogel mimicking the actuator function and an insulin (drug) sensor. In this work, the results of functional testing of individual amperometric glucose and insulin sensors as well as an impedimetric sensor for the detection of the hydrogel swelling/shrinking are presented.
Effect of O2 plasma on properties of electrolyte-insulator-semiconductor structures (2017)
Arreola, Julio ; Keusgen, Michael ; Schöning, Michael Josef
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.
Detection of plant virus particles with a capacitive field-effect sensor (2021)
Jablonski, Melanie ; Poghossian, Arshak ; Keusgen, Michael ; Wege, Christina ; Schöning, Michael Josef
Plant viruses are major contributors to crop losses and induce high economic costs worldwide. For reliable, on-site and early detection of plant viral diseases, portable biosensors are of great interest. In this study, a field-effect SiO2-gate electrolyte-insulator-semiconductor (EIS) sensor was utilized for the label-free electrostatic detection of tobacco mosaic virus (TMV) particles as a model plant pathogen. The capacitive EIS sensor has been characterized regarding its TMV sensitivity by means of constant-capacitance method. The EIS sensor was able to detect biotinylated TMV particles from a solution with a TMV concentration as low as 0.025 nM. A good correlation between the registered EIS sensor signal and the density of adsorbed TMV particles assessed from scanning electron microscopy images of the SiO2-gate chip surface was observed. Additionally, the isoelectric point of the biotinylated TMV particles was determined via zeta potential measurements and the influence of ionic strength of the measurement solution on the TMV-modified EIS sensor signal has been studied.
Towards a biosensor to monitor the sterilisation efficiency of aseptic filling machines (2015)
Oberländer, Jan ; Bromm, Alexander ; Wendeler, Luisa ; Iken, Heiko ; Palomar Duran, Marlena ; Greeff, Anton ; Kirchner, Patrick ; Keusgen, Michael ; Schöning, Michael Josef
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.
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