TY - JOUR A1 - Arreola, Julio A1 - Oberländer, Jan A1 - Mätzkow, M. A1 - Keusgen, Michael A1 - Schöning, Michael Josef T1 - Surface functionalization for spore-based biosensors with organosilanes JF - Electrochimica Acta N2 - In the present work, surface functionalization of different sensor materials was studied. Organosilanes are well known to serve as coupling agent for biomolecules or cells on inorganic materials. 3-aminopropyltriethoxysilane (APTES) was used to attach microbiological spores time to an interdigitated sensor surface. The functionality and physical properties of APTES were studied on isolated sensor materials, namely silicon dioxide (SiO2) and platinum (Pt) as well as the combined material on sensor level. A predominant immobilization of spores could be demonstrated on SiO2 surfaces. Additionally, the impedance signal of APTES-functionalized biosensor chips has been investigated. Y1 - 2017 U6 - http://dx.doi.org/10.1016/j.electacta.2017.04.157 SN - 0013-4686 VL - 241 SP - 237 EP - 243 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Bronder, Thomas A1 - Poghossian, Arshak A1 - Keusgen, Michael A1 - Schöning, Michael Josef T1 - Label-free detection of double-stranded DNA molecules with polyelectrolyte-modified capacitive field-effect sensors T1 - Markierungsfreie Detektion doppelsträngiger DNA Moleküle mit Hilfe von Polyelektrolyt-modifizierten kapazitiven Feldeffekt-Sensoren JF - tm - Technisches Messen N2 - In this study, polyelectrolyte-modified field-effect-based electrolyte-insulator-semiconductor (EIS) devices have been used for the label-free electrical detection of double-stranded deoxyribonucleic acid (dsDNA)molecules. The sensor-chip functionalization with a positively charged polyelectrolyte layer provides the possibility of direct adsorptive binding of negatively charged target DNA oligonucleotides onto theSiO2-chip surface.EIS sensors can be utilized as a tool to detect surface-charge changes; the electrostatic adsorption of oligonucleotides onto the polyelectrolyte layer leads to a measureable surface-potential change. Signals of 39mV have been recorded after the incubation with the oligonucleotide solution. Besides the electrochemical experiments, the successful adsorption of dsDNA onto the polyelectrolyte layer has been verified via fluorescence microscopy. The presented results demonstrate that the signal recording of EISchips, which are modified with a polyelectrolyte layer, canbe used as a favorable approach for a fast, cheap and simple detection method for dsDNA. Y1 - 2017 U6 - http://dx.doi.org/10.1515/teme-2017-0015 VL - 84 IS - 10 SP - 628 EP - 634 PB - De Gruyter CY - Oldenbourg ER - TY - CHAP A1 - Oberländer, Jan A1 - Arreola, Julio A1 - Hansen, Christina A1 - Greeff, Anton A1 - Mayer, Marlena A1 - Keusgen, Michael A1 - Schöning, Michael Josef T1 - Impedimetric Biosensor to Enable Fast Evaluation of Gaseous Sterilization Processes T2 - MDPI Proceedings Y1 - 2017 U6 - http://dx.doi.org/10.3390/proceedings1040435 N1 - Eurosensors 2017 Conference, Paris, France, 3–6 September 2017 VL - 1 IS - 4 ER - TY - CHAP A1 - Molinnus, Denise A1 - Hardt, Gabriel A1 - Käver, Larissa A1 - Willenberg, Holger S. A1 - Poghossian, Arshak A1 - Keusgen, Michael A1 - Schöning, Michael Josef T1 - Detection of Adrenaline Based on Bioelectrocatalytical System to Support Tumor Diagnostic Technology T2 - MDPI Proceedings Y1 - 2017 U6 - http://dx.doi.org/10.3390/proceedings1040506 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 - Figueroa-Miranda, Gabriela A1 - Feng, Lingyan A1 - Shiu, Simon Chi-Chin A1 - Dirkzwager, Roderick Marshall A1 - Cheung, Yee-Wai A1 - Tanner, Julian Alexander A1 - Schöning, Michael Josef A1 - Offenhäusser, Andreas A1 - Mayer, Dirk T1 - Aptamer-based electrochemical biosensor for highly sensitive and selective malaria detection with adjustable dynamic response range and reusability JF - Sensor and Actuators B: Chemical N2 - Malaria infection remains a significant risk for much of the population of tropical and subtropical areas, particularly in developing countries. Therefore, it is of high importance to develop sensitive, accurate and inexpensive malaria diagnosis tests. Here, we present a novel aptamer-based electrochemical biosensor (aptasensor) for malaria detection by impedance spectroscopy, through the specific recognition between a highly discriminatory DNA aptamer and its target Plasmodium falciparum lactate dehydrogenase (PfLDH). Interestingly, due to the isoelectric point (pI) of PfLDH, the aptasensor response showed an adjustable detection range based on the different protein net-charge at variable pH environments. The specific aptamer recognition allows sensitive protein detection with an expanded detection range and a low detection limit, as well as a high specificity for PfLDH compared to analogous proteins. The specific feasibility of the aptasensor is further demonstrated by detection of the target PfLDH in human serum. Furthermore, the aptasensor can be easily regenerated and thus applied for multiple usages. The robustness, sensitivity, and reusability of the presented aptasensor make it a promising candidate for point-of-care diagnostic systems. Y1 - 2018 U6 - http://dx.doi.org/10.1016/j.snb.2017.07.117 SN - 0925-4005 VL - 255 IS - P1 SP - 235 EP - 243 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Morais, Paulo V. A1 - Gomes, Vanderley F., Jr. A1 - Silva, Anielle C. A. A1 - Dantas, Noelio O. A1 - Schöning, Michael Josef A1 - Siqueira, José R., Jr. T1 - Nanofilm of ZnO nanocrystals/carbon nanotubes as biocompatible layer for enzymatic biosensors in capacitive field-effect devices JF - Journal of Materials Science N2 - The incorporation of nanomaterials that are biocompatible with different types of biological compounds has allowed the development of a new generation of biosensors applied especially in the biomedical field. In particular, the integration of film-based nanomaterials employed in field-effect devices can be interesting to develop biosensors with enhanced properties. In this paper, we studied the fabrication of sensitive nanofilms combining ZnO nanocrystals and carbon nanotubes (CNTs), prepared by means of the layer-by-layer (LbL) technique, in a capacitive electrolyte-insulator-semiconductor (EIS) structure for detecting glucose and urea. The ZnO nanocrystals were incorporated in a polymeric matrix of poly(allylamine) hydrochloride (PAH), and arranged with multi-walled CNTs in a LbL PAH-ZnO/CNTs film architecture onto EIS chips. The electrochemical characterizations were performed by capacitance–voltage and constant capacitance measurements, while the morphology of the films was characterized by atomic force microscopy. The enzymes glucose oxidase and urease were immobilized on film’s surface for detection of glucose and urea, respectively. In order to obtain glucose and urea biosensors with optimized amount of sensitive films, we investigated the ideal number of bilayers for each detection system. The glucose biosensor showed better sensitivity and output signal for an LbL PAH-ZnO/CNTs nanofilm with 10 bilayers. On the other hand, the urea biosensor presented enhanced properties even for the first bilayer, exhibiting high sensitivity and output signal. The presence of the LbL PAH-ZnO/CNTs films led to biosensors with better sensitivity and enhanced response signal, demonstrating that the adequate use of nanostructured films is feasible for proof-of-concept biosensors with improved properties that may be employed for biomedical applications. Y1 - 2017 U6 - http://dx.doi.org/10.1007/s10853-017-1369-y SN - 1573-4803 VL - 52 IS - 20 SP - 12314 EP - 12325 PB - Springer CY - Berlin ER - TY - JOUR A1 - Dantism, Shahriar A1 - Takenaga, Shoko A1 - Wagner, Torsten A1 - Wagner, Patrick A1 - Schöning, Michael Josef T1 - Differential imaging of the metabolism of bacteria and eukaryotic cells based on light-addressable potentiometric sensors JF - Electrochimica Acta N2 - A light-addressable potentiometric sensor (LAPS) is a field-effect-based potentiometric sensor with an electrolyte/insulator/semiconductor (EIS) structure, which is able to monitor analyte concentrations of (bio-)chemical species in aqueous solutions in a spatially resolved way. Therefore, it is also an appropriate tool to record 2D-chemical images of concentration variations on the sensor surface. In the present work, two differential, LAPS-based measurement principles are introduced to determine the metabolic activity of Escherichia coli (E. coli) K12 and Chinese hamster ovary (CHO) cells as test microorganisms. Hereby, we focus on i) the determination of the extracellular acidification rate (ΔpH/min) after adding glucose solutions to the cell suspensions; and ii) recording the amplitude increase of the photocurrent (Iph) related to the produced acids from E. coli K12 bacteria and CHO cells on the sensor surface by 2D-chemical imaging. For this purpose, 3D-printed multi-chamber structures were developed and mounted on the planar sensor-chip surface to define four independent compartments, enabling differential measurements with varying cell concentrations. The differential concept allows eliminating unwanted drift effects and, with the four-chamber structures, measurements on the different cell concentrations were performed simultaneously, thus reducing also the overall measuring time. Y1 - 2017 U6 - http://dx.doi.org/10.1016/j.electacta.2017.05.196 SN - 0013-4686 VL - 246 SP - 234 EP - 241 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Jildeh, Zaid B. A1 - Kirchner, Patrick A1 - Oberländer, Jan A1 - Kremers, Alexander A1 - Wagner, Torsten A1 - Wagner, Patrick H. A1 - Schöning, Michael Josef T1 - FEM-based modeling of a calorimetric gas sensor for hydrogen peroxide monitoring JF - physica status solidi a : applications and materials sciences N2 - A physically coupled finite element method (FEM) model is developed to study the response behavior of a calorimetric gas sensor. The modeled sensor serves as a monitoring device of the concentration of gaseous hydrogen peroxide (H2 O2) in a high temperature mixture stream in aseptic sterilization processes. The principle of operation of a calorimetric H2 O2 sensor is analyzed and the results of the numerical model have been validated by using previously published sensor experiments. The deviation in the results between the FEM model and experimental data are presented and discussed. Y1 - 2017 U6 - http://dx.doi.org/10.1002/pssa.201600912 SN - 1862-6319 IS - Early View PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Molinnus, Denise A1 - Poghossian, Arshak A1 - Keusgen, Michael A1 - Katz, Evgeny A1 - Schöning, Michael Josef T1 - Coupling of Biomolecular Logic Gates with Electronic Transducers: From Single Enzyme Logic Gates to Sense/Act/Treat Chips JF - Electroanalysis N2 - The integration of biomolecular logic principles with electronic transducers allows designing novel digital biosensors with direct electrical output, logically triggered drug-release, and closed-loop sense/act/treat systems. This opens new opportunities for advanced personalized medicine in the context of theranostics. In the present work, we will discuss selected examples of recent developments in the field of interfacing enzyme logic gates with electrodes and semiconductor field-effect devices. Special attention is given to an enzyme OR/Reset logic gate based on a capacitive field-effect electrolyte-insulator-semiconductor sensor modified with a multi-enzyme membrane. Further examples are a digital adrenaline biosensor based on an AND logic gate with binary YES/NO output and an integrated closed-loop sense/act/treat system comprising an amperometric glucose sensor, a hydrogel actuator, and an insulin (drug) sensor. Y1 - 2017 U6 - http://dx.doi.org/10.1002/elan.201700208 SN - 1521-4109 VL - 29 IS - 8 SP - 1840 EP - 1849 PB - Wiley CY - Weinheim ER -