TY - JOUR A1 - Wu, Chunsheng A1 - Poghossian, Arshak A1 - Bronder, Thomas A1 - Schöning, Michael Josef T1 - Sensing of double-stranded DNA molecules by their intrinsic molecular charge using the light-addressable potentiometric sensor JF - Sensors and Actuators B: Chemical N2 - A multi-spot light-addressable potentiometric sensor (LAPS), which belongs to the family of semiconductor field-effect devices, was applied for label-free detection of double-stranded deoxyribonucleic acid (dsDNA) molecules by their intrinsic molecular charge. To reduce the distance between the DNA charge and sensor surface and thus, to enhance the electrostatic coupling between the dsDNA molecules and the LAPS, the negatively charged dsDNA molecules were electrostatically adsorbed onto the gate surface of the LAPS covered with a positively charged weak polyelectrolyte layer of PAH (poly(allylamine hydrochloride)). The surface potential changes in each spot of the LAPS, induced by the layer-by-layer adsorption of a PAH/dsDNA bilayer, were recorded by means of photocurrent-voltage and constant-photocurrent measurements. In addition, the surface morphology of the gate surface before and after consecutive electrostatic adsorption of PAH and dsDNA layers was studied by atomic force microscopy measurements. Moreover, fluorescence microscopy was used to verify the successful adsorption of dsDNA molecules onto the PAH-modified LAPS surface. A high sensor signal of 25 mV was registered after adsorption of 10 nM dsDNA molecules. The lower detection limit is down to 0.1 nM dsDNA. The obtained results demonstrate that the PAH-modified LAPS device provides a convenient and rapid platform for the direct label-free electrical detection of in-solution hybridized dsDNA molecules. KW - Layer-by-layer adsorption KW - Poly(allylamine hydrochloride) KW - Label-free detection KW - DNA biosensor KW - LAPS KW - Field effect Y1 - 2016 U6 - http://dx.doi.org/10.1016/j.snb.2016.02.004 SN - 0925-4005 IS - 229 SP - 506 EP - 512 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Wagner, Torsten A1 - Vornholt, Wolfgang A1 - Werner, Frederik A1 - Yoshinobu, Tatsuo A1 - Miyamoto, Ko-Ichiro A1 - Keusgen, Michael A1 - Schöning, Michael Josef T1 - Light-addressable potentiometric sensor (LAPS) combined with magnetic beads for pharmaceutical screening JF - Physics in medicine N2 - The light-addressable potentiometric sensor (LAPS) has the unique feature to address different regions of a sensor surface without the need of complex structures. Measurements at different locations on the sensor surface can be performed in a common analyte solution, which distinctly simplifies the fluidic set-up. However, the measurement in a single analyte chamber prevents the application of different drugs or different concentrations of a drug to each measurement spot at the same time as in the case of multi-reservoir-based set-ups. In this work, the authors designed a LAPS-based set-up for cell culture screening that utilises magnetic beads loaded with the endotoxin (lipopolysaccharides, LPS), to generate a spatially distributed gradient of analyte concentration. Different external magnetic fields can be adjusted to move the magnetic beads loaded with a specific drug within the measurement cell. By recording the metabolic activities of a cell layer cultured on top of the LAPS surface, this work shows the possibility to apply different concentrations of a sample along the LAPS measurement spots within a common analyte solution. Y1 - 2016 U6 - http://dx.doi.org/10.1016/j.phmed.2016.03.001 SN - 2352-4510 VL - 2016 IS - 1 SP - 2 EP - 7 ER - TY - JOUR A1 - Doll, Theodor A1 - Wagner, Torsten A1 - Wagner, Patrick A1 - Schöning, Michael Josef T1 - Engineering of functional interfaces / Theodor Doll ; Torsten Wagner ; Patrick Wagner ; Michael J. Schöning (eds.) JF - Physica status solidi (a) Y1 - 2016 U6 - http://dx.doi.org/10.1002/pssa.201670641 SN - 1862-6319 VL - 213 IS - 6 SP - 1393 EP - 1394 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Molinnus, Denise A1 - Sorich, Maren A1 - Bartz, Alexander A1 - Siegert, Petra A1 - Willenberg, Holger S. A1 - Lisdat, Fred A1 - Poghossian, Arshak A1 - Keusgen, Michael A1 - Schöning, Michael Josef T1 - Towards an adrenaline biosensor based on substrate recycling amplification in combination with an enzyme logic gate JF - Sensors and Actuators B: Chemical N2 - An amperometric biosensor using a substrate recycling principle was realized for the detection of low adrenaline concentrations (1 nM) by measurements in phosphate buffer and Ringer’s solution at pH 6.5 and pH 7.4, respectively. In proof-of-concept experiments, a Boolean logic-gate principle has been applied to develop a digital adrenaline biosensor based on an enzyme AND logic gate. The obtained results demonstrate that the developed digital biosensor is capable for a rapid qualitative determination of the presence/absence of adrenaline in a YES/NO statement. Such digital biosensor could be used in clinical diagnostics for the control of a correct insertion of a catheter in the adrenal veins during adrenal venous-sampling procedure. Y1 - 2016 U6 - http://dx.doi.org/10.1016/j.snb.2016.06.064 SN - 0925-4005 VL - 237 SP - 190 EP - 195 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Miyamoto, Ko-Ichiro A1 - Sato, Takuya A1 - Abe, Minami A1 - Wagner, Torsten A1 - Schöning, Michael Josef A1 - Yoshinobu, Tatsuo T1 - Light-addressable potentiometric sensor as a sensing element in plug-based microfluidic devices JF - Micromachines N2 - A plug-based microfluidic system based on the principle of the light-addressable potentiometric sensor (LAPS) is proposed. The LAPS is a semiconductor-based chemical sensor, which has a free addressability of the measurement point on the sensing surface. By combining a microfluidic device and LAPS, ion sensing can be performed anywhere inside the microfluidic channel. In this study, the sample solution to be measured was introduced into the channel in a form of a plug with a volume in the range of microliters. Taking advantage of the light-addressability, the position of the plug could be monitored and pneumatically controlled. With the developed system, the pH value of a plug with a volume down to 400 nL could be measured. As an example of plug-based operation, two plugs were merged in the channel, and the pH change was detected by differential measurement. KW - light-addressable potentiometric sensor KW - plug-based microfluidic device KW - chemical sensor Y1 - 2016 U6 - http://dx.doi.org/10.3390/mi7070111 SN - 2072-666X N1 - This article belongs to the Special Issue "Micro/Nano Devices for Chemical Analysis" VL - 7 IS - 7 SP - 111 PB - MDPI CY - Basel ER - TY - JOUR A1 - Reisert, Steffen A1 - Geissler, H. A1 - Weiler, C. A1 - Wagner, P. A1 - Schöning, Michael Josef T1 - Multiple sensor-type system for monitoring the microbicidal effectiveness of aseptic sterilisation processes JF - Food control N2 - The present work describes a novel multiple sensor-type system for the real-time analysis of aseptic sterilisation processes employing gaseous hydrogen peroxide (H2O2) as a sterilant. The inactivation kinetics of Bacillus atrophaeus by gaseous H2O2 have been investigated by means of a methodical calibration experiment, taking into account the process variables H2O2 concentration, humidity and gas temperature. It has been found that the microbicidal effectiveness at H2O2 concentrations above 2% v/v is largely determined by the concentration itself, while at lower H2O2 concentrations, the gas temperature and humidity play a leading role. Furthermore, the responses of different types of gas sensors towards the influencing factors of the sterilisation process have been analysed within the same experiment. Based on a correlation established between the inactivation kinetics and the sensor responses, a calorimetric H2O2 sensor and a metal-oxide semiconductor (MOX) sensor have been identified as possible candidates for monitoring the microbicidal effectiveness of aseptic sterilisation processes employing gaseous H2O2. Therefore, two linear models that describe the relationship between sensor response and microbicidal effectiveness have been proposed. Y1 - 2015 U6 - http://dx.doi.org/10.1016/j.foodcont.2014.07.063 SN - 1873-7129 (E-Journal); 0956-7135 (Print) VL - 47 SP - 615 EP - 622 ER - TY - JOUR A1 - Yoshinobu, Tatsuo A1 - Miyamoto, Ko-ichiro A1 - Wagner, Torsten A1 - Schöning, Michael Josef T1 - Recent developments of chemical imaging sensor systems based on the principle of the light-addressable potentiometric sensor JF - Sensors and actuators B: Chemical N2 - The light-addressable potentiometric sensor (LAPS) is an electrochemical sensor with a field-effect structure to detect the variation of the Nernst potential at its sensor surface, the measured area on which is defined by illumination. Thanks to this light-addressability, the LAPS can be applied to chemical imaging sensor systems, which can visualize the two-dimensional distribution of a particular target ion on the sensor surface. Chemical imaging sensor systems are expected to be useful for analysis of reaction and diffusion in various electrochemical and biological samples. Recent developments of LAPS-based chemical imaging sensor systems, in terms of the spatial resolution, measurement speed, image quality, miniaturization and integration with microfluidic devices, are summarized and discussed. Y1 - 2015 U6 - http://dx.doi.org/10.1016/j.snb.2014.09.002 SN - 1873-3077 (E-Journal); 0925-4005 (Print) VL - 207, Part B SP - 926 EP - 932 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Poghossian, Arshak A1 - Bäcker, Matthias A1 - Mayer, Dirk A1 - Schöning, Michael Josef T1 - Gating capacitive field-effect sensors by the charge of nanoparticle/molecule hybrids JF - Nanoscale Y1 - 2015 U6 - http://dx.doi.org/10.1039/C4NR05987E SN - 2040-3372 (E-Journal); 2040-3364 (Print) SP - 1023 EP - 1031 PB - Royal Society of Chemistry (RSC) CY - Cambridge ER - TY - JOUR A1 - Schusser, Sebastian A1 - Poghossian, Arshak A1 - Bäcker, Matthias A1 - Krischer, M. A1 - Leinhos, Marcel A1 - Wagner, P. A1 - Schöning, Michael Josef T1 - An application of field-effect sensors for in-situ monitoring of degradation of biopolymers JF - Sensors and actuators B: Chemical N2 - The characterization of the degradation kinetics of biodegradable polymers is mandatory with regard to their proper application. In the present work, polymer-modified electrolyte–insulator–semiconductor (PMEIS) field-effect sensors have been applied for in-situ monitoring of the pH-dependent degradation kinetics of the commercially available biopolymer poly(d,l-lactic acid) (PDLLA) in buffer solutions from pH 3 to pH 13. PDLLA films of 500 nm thickness were deposited on the surface of an Al–p-Si–SiO2–Ta2O5 structure from a polymer solution by means of spin-coating method. The PMEIS sensor is, in principle, capable to detect any changes in bulk, surface and interface properties of the polymer induced by degradation processes. A faster degradation has been observed for PDLLA films exposed to alkaline solutions (pH 9, pH 11 and pH 13). Y1 - 2015 U6 - http://dx.doi.org/10.1016/j.snb.2014.10.058 SN - 1873-3077 (E-Journal); 0925-4005 (Print) VL - 207, Part B SP - 954 EP - 959 PB - Elsevier CY - Amsterdam 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 - Wu, Chunsheng A1 - Bronder, Thomas A1 - Poghossian, Arshak A1 - Werner, Frederik A1 - Schöning, Michael Josef T1 - Label-free detection of DNA using light-addressable potentiometric sensor modified with a positively charged polyelectrolyte layer JF - Nanoscale N2 - A multi-spot (16 spots) light-addressable potentiometric sensor (MLAPS) consisting of an Al–p-Si–SiO2 structure modified with a weak polyelectrolyte layer of PAH (poly(allylamine hydrochloride)) was applied for the label-free electrical detection of DNA (deoxyribonucleic acid) immobilization and hybridization by the intrinsic molecular charge for the first time. To achieve a preferentially flat orientation of DNA strands and thus, to reduce the distance between the DNA charge and MLAPS surface, the negatively charged probe single-stranded DNAs (ssDNA) were electrostatically adsorbed onto the positively charged PAH layer using a simple layer-by-layer (LbL) technique. In this way, more DNA charge can be positioned within the Debye length, yielding a higher sensor signal. The surface potential changes in each spot induced due to the surface modification steps (PAH adsorption, probe ssDNA immobilization, hybridization with complementary target DNA (cDNA), non-specific adsorption of mismatched ssDNA) were determined from the shifts of photocurrent–voltage curves along the voltage axis. A high sensor signal of 83 mV was registered after immobilization of probe ssDNA onto the PAH layer. The hybridization signal increases from 5 mV to 32 mV with increasing the concentration of cDNA from 0.1 nM to 5 μM. In contrast, a small signal of 5 mV was recorded in the case of non-specific adsorption of fully mismatched ssDNA (5 μM). The obtained results demonstrate the potential of the MLAPS in combination with the simple and rapid LbL immobilization technique as a promising platform for the future development of multi-spot light-addressable label-free DNA chips with direct electrical readout. Y1 - 2015 U6 - http://dx.doi.org/10.1039/C4NR07225A VL - 14 IS - 7 SP - 6143 EP - 6150 PB - Royal Society of Chemistry (RSC) CY - Cambridge 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 - http://dx.doi.org/10.1002/pssa.201431891 SN - 1862-6319 VL - 212 IS - 6 SP - 1353 EP - 1358 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Poghossian, Arshak A1 - Katz, Evgeny A1 - Schöning, Michael Josef T1 - Enzyme logic AND-Reset and OR-Reset gates based on a field-effect electronic transducer modified with multi-enzyme membrane JF - Chemical Communications N2 - Capacitive field-effect sensors modified with a multi-enzyme membrane have been applied for an electronic transduction of biochemical signals processed by enzyme-based AND-Reset and OR-Reset logic gates. The local pH change at the sensor surface induced by the enzymatic reaction was used for the activation of the Reset function for the first time. Y1 - 2015 U6 - http://dx.doi.org/10.1039/C5CC01362C VL - 51 SP - 6564 EP - 6567 PB - Royal Society of Chemistry (RSC) CY - Cambridge 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 - 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 - http://dx.doi.org/10.1002/pssa.201431911 SN - 1862-6319 VL - 212 IS - 6 SP - 1259 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Jildeh, Zaid B. A1 - Wagner, Torsten A1 - Schöning, Michael Josef A1 - Pieper, Martin T1 - Simulating the electromagnetic‐thermal treatment of thin aluminium layers for adhesion improvement JF - Physica status solidi (a) N2 - A composite layer material used in packaging industry is made from joining layers of different materials using an adhesive. An important processing step in the production of aluminium-containing composites is the surface treatment and consequent coating of adhesive material on the aluminium surface. To increase adhesion strength between aluminium layer and the adhesive material, the foil is heat treated. For efficient heating, induction heating was considered as state-of-the-art treatment process. Due to the complexity of the heating process and the unpredictable nature of the heating source, the control of the process is not yet optimised. In this work, a finite element analysis of the process was established and various process parameters were studied. The process was simplified and modelled in 3D. The numerical model contains an air domain, an aluminium layer and a copper coil fitted with a magnetic field concentrating material. The effect of changing the speed of the aluminium foil (or rolling speed) was studied with the change of the coil current. Statistical analysis was used for generating a general control equation of coil current with changing rolling speed. Y1 - 2015 U6 - http://dx.doi.org/10.1002/pssa.201431893 SN - 1862-6319 VL - Vol. 212 IS - 6 SP - 1234 EP - 1241 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Pilas, Johanna A1 - Iken, Heiko A1 - Selmer, Thorsten A1 - Keusgen, Michael A1 - Schöning, Michael Josef T1 - Development of a multi‐parameter sensor chip for the simultaneous detection of organic compounds in biogas processes JF - Physica status solidi (a) N2 - 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. Y1 - 2015 U6 - http://dx.doi.org/10.1002/pssa.201431894 SN - 1862-6319 VL - 212 IS - 6 SP - 1306 EP - 1312 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Breuer, Lars A1 - Raue, Markus A1 - Kirschbaum, M. A1 - Mang, Thomas A1 - Schöning, Michael Josef A1 - Thoelen, R. A1 - Wagner, Torsten T1 - Light-controllable polymeric material based on temperature-sensitive hydrogels with incorporated graphene oxide JF - Physica status solidi (a) N2 - Poly(N-isopropylacrylamide) (PNIPAAm) hydrogel films with incorporated graphene oxide (GO) were developed and tested as light-stimulated actuators. GO dispersions were synthesized via Hummers method and characterized toward their optical properties and photothermal energy conversion. The hydrogels were prepared by means of photopolymerization. In addition, the influence of GO within the hydrogel network on the lower critical solution temperature (LCST) was investigated by differential scanning calorimetry (DSC). The optical absorbance and the response to illumination were determined as a function of GO concentration for thin hydrogel films. A proof of principle for the stimulation with light was performed. Y1 - 2015 U6 - http://dx.doi.org/10.1002/pssa.201431944 SN - 1862-6319 VL - 212 IS - 6 SP - 1368 EP - 1374 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Dantism, S. A1 - Takenaga, S. A1 - Wagner, P. A1 - Wagner, Torsten A1 - Schöning, Michael Josef T1 - Light-addressable Potentiometric Sensor (LAPS) Combined with Multi-chamber Structures to Investigate the Metabolic Activity of Cells JF - Procedia Engineering N2 - LAPS are field-effect-based potentiometric sensors which are able to monitor analyte concentrations in a spatially resolved manner. Hence, a LAPS sensor system is a powerful device to record chemical imaging of the concentration of chemical species in an aqueous solution, chemical reactions, or the growth of cell colonies on the sensor surface, to record chemical images. In this work, multi-chamber 3D-printed structures made out of polymer (PP-ABS) were combined with LAPS chips to analyse differentially and simultaneously the metabolic activity of Escherichia coli K12 and Chinese hamster ovary (CHO) cells, and the responds of those cells to the addition of glucose solution. Y1 - 2015 U6 - http://dx.doi.org/10.1016/j.proeng.2015.08.647 SN - 1877-7058 N1 - Part of special issue "Eurosensors 2015" VL - 120 SP - 384 EP - 387 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Molinnus, Denise A1 - Bäcker, Matthias A1 - Siegert, Petra A1 - Willenberg, H. A1 - Poghossian, Arshak A1 - Keusgen, M. A1 - Schöning, Michael Josef T1 - Detection of Adrenaline Based on Substrate Recycling Amplification JF - Procedia Engineering N2 - An amperometric enzyme biosensor has been applied for the detection of adrenaline. The adrenaline biosensor has been prepared by modification of an oxygen electrode with the enzyme laccase that operates at a broad pH range between pH 3.5 to pH 8. The enzyme molecules were immobilized via cross-linking with glutaraldehyde. The sensitivity of the developed adrenaline biosensor in different pH buffer solutions has been studied. Y1 - 2015 U6 - http://dx.doi.org/10.1016/j.proeng.2015.08.708 SN - 1877-7058 N1 - Eurosensors 2015 VL - 120 SP - 540 EP - 543 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Schusser, Sebastian A1 - Krischer, M. A1 - Molin, D. G. M. A1 - Akker, N. M. S. van den A1 - Bäcker, Matthias A1 - Poghossian, Arshak A1 - Schöning, Michael Josef T1 - Sensor System for in-situ and Real-time Monitoring of Polymer (bio) degradation JF - Procedia Engineering N2 - A sensor system for investigating (bio)degradationprocesses of polymers is presented. The system utilizes semiconductor field-effect sensors and is capable of monitoring the degradation process in-situ and in real-time. The degradation of the polymer poly(d,l-lactic acid) is exemplarily monitored in solutions with different pH value, pH-buffer solution containing the model enzyme lipase from Rhizomucormiehei and cell-culture medium containing supernatants from stimulated and non-stimulated THP-1-derived macrophages mimicking activation of the immune system. Y1 - 2015 U6 - http://dx.doi.org/10.1016/j.proeng.2015.08.815 SN - 1877-7058 N1 - Eurosensors 2015 VL - 120 SP - 948 EP - 951 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Pilas, Johanna A1 - Mariano, K. A1 - Keusgen, M. A1 - Selmer, Thorsten A1 - Schöning, Michael Josef T1 - Optimization of an Enzyme-based Multi-parameter Biosensor for Monitoring Biogas Processes JF - Procedia Engineering Y1 - 2015 U6 - http://dx.doi.org/10.1016/j.proeng.2015.08.702 SN - 1877-7058 N1 - Part of special issue "Eurosensors 2015" VL - 120 SP - 532 EP - 535 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Miyamoto, Ko-ichiro A1 - Bing, Yu A1 - Wagner, Torsten A1 - Yoshinobu, Tatsuo A1 - Schöning, Michael Josef T1 - Visualization of Defects on a Cultured Cell Layer by Utilizing Chemical Imaging Sensor JF - Procedia Engineering N2 - The chemical imaging sensor is a field-effect sensor which is able to visualize both the distribution of ions (in LAPS mode) and the distribution of impedance (in SPIM mode) inthe sample. In this study, a novel wound-healing assay is proposed, in which the chemical imaging sensor operated in SPIM mode is applied to monitor the defect of a cell layer brought into proximity of the sensing surface.A reduced impedance inside the defect, which was artificially formed ina cell layer, was successfully visualized in a photocurrent image. Y1 - 2015 U6 - http://dx.doi.org/10.1016/j.proeng.2015.08.806 SN - 1877-7058 N1 - Part of special issue "Eurosensors 2015" VL - 120 SP - 936 EP - 939 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Bronder, Thomas A1 - Poghossian, Arshak A1 - Scheja, S. A1 - Wu, Chunsheng A1 - Keusgen, M. A1 - Schöning, Michael Josef T1 - Electrostatic Detection of Unlabelled Single- and Double-stranded DNA Using Capacitive Field-effect Devices Functionalized with a Positively Charged Polyelectrolyte Layer JF - Procedia Engineering N2 - 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. Y1 - 2015 U6 - http://dx.doi.org/10.1016/j.proeng.2015.08.710 SN - 1877-7058 N1 - Eurosensors 2015 VL - 120 SP - 544 EP - 547 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Takenaga, Shoko A1 - Schneider, Benno A1 - Erbay, E. A1 - Biselli, Manfred A1 - Schnitzler, Thomas A1 - Schöning, Michael Josef A1 - Wagner, Torsten T1 - Fabrication of biocompatible lab-on-chip devices for biomedical applications by means of a 3D-printing process JF - Physica status solidi (a) N2 - A new microfluidic assembly method for semiconductor-based biosensors using 3D-printing technologies was proposed for a rapid and cost-efficient design of new sensor systems. The microfluidic unit is designed and printed by a 3D-printer in just a few hours and assembled on a light-addressable potentiometric sensor (LAPS) chip using a photo resin. The cell growth curves obtained from culturing cells within microfluidics-based LAPS systems were compared with cell growth curves in cell culture flasks to examine biocompatibility of the 3D-printed chips. Furthermore, an optimal cell culturing within microfluidics-based LAPS chips was achieved by adjusting the fetal calf serum concentrations of the cell culture medium, an important factor for the cell proliferation. Y1 - 2015 U6 - http://dx.doi.org/10.1002/pssa.201532053 SN - 1862-6319 VL - 212 IS - 6 SP - 1347 EP - 1352 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Molinnus, Denise A1 - Bäcker, Matthias A1 - Iken, Heiko A1 - Poghossian, Arshak A1 - Keusgen, Michael A1 - Schöning, Michael Josef T1 - Concept for a biomolecular logic chip with an integrated sensor and actuator function JF - Physica status solidi (a) N2 - 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. Y1 - 2015 U6 - http://dx.doi.org/10.1002/pssa.201431913 SN - 1862-6319 VL - 212 IS - 6 SP - 1382 EP - 1388 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Warmer, Johannes A1 - Wagner, Patrick A1 - Schöning, Michael Josef A1 - Kaul, Peter T1 - Detection of triacetone triperoxide using temperature cycled metal-oxide semiconductor gas sensors JF - Physica status solidi (a) Y1 - 2015 U6 - http://dx.doi.org/10.1002/pssa.201431882 SN - 1862-6319 VL - 212 IS - 6 SP - 1289 EP - 1298 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Delle, Lotta E. A1 - Huck, Christina A1 - Bäcker, Matthias A1 - Müller, Frank A1 - Grandthyll, Samuel A1 - Jacobs, Karin A1 - Lilischkis, Rainer A1 - Vu, Xuan T. A1 - Schöning, Michael Josef A1 - Wagner, Patrick A1 - Thoelen, Roland A1 - Weil, Maryam A1 - Ingebrandt, Sven T1 - Impedimetric immunosensor for the detection of histamine based on reduced graphene oxide JF - Physica status solidi (a) Y1 - 2015 U6 - http://dx.doi.org/10.1002/pssa.201431863 SN - 1862-6319 VL - 212 IS - 6 SP - 1327 EP - 1334 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Bronder, Thomas A1 - Poghossian, Arshak A1 - Scheja, Sabrina A1 - Wu, Chunsheng A1 - Keusgen, Michael A1 - Mewes, Dieter A1 - Schöning, Michael Josef T1 - DNA Immobilization and Hybridization Detection by the Intrinsic Molecular Charge Using Capacitive Field-Effect Sensors Modified with a Charged Weak Polyelectrolyte Layer JF - Applied Materials & Interfaces N2 - 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. Y1 - 2015 U6 - http://dx.doi.org/10.1021/acsami.5b05146 VL - 36 IS - 7 SP - 20068 EP - 20075 PB - American Chemical Society CY - Washington, DC 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 - 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 - http://dx.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 - Miyamato, Ko-ichiro A1 - Sakakita, Sakura A1 - Wagner, Torsten A1 - Schöning, Michael Josef A1 - Yoshinobu, Tatsuo T1 - Application of chemical imaging sensor to in-situ pH imaging in the vicinity of a corroding metal surface JF - Electrochimica Acta N2 - The chemical imaging sensor was applied to in-situ pH imaging of the solution in the vicinity of a corroding surface of stainless steel under potentiostatic polarization. A test piece of polished stainless steel was placed on the sensing surface leaving a narrow gap filled with artificial seawater and the stainless steel was corroded under polarization. The pH images obtained during polarization showed correspondence between the region of lower pH and the site of corrosion. It was also found that the pH value in the gap became as low as 2 by polarization, which triggered corrosion. Y1 - 2015 U6 - http://dx.doi.org/10.1016/j.electacta.2015.07.184 SN - 0013-4686 VL - 183 SP - 137 EP - 142 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 - Bandodkar, Amay J. A1 - Molinnus, Denise A1 - Mirza, Omar A1 - Guinovart, Tomas A1 - Windmiller, Joshua R. A1 - Valdes-Ramirez, Gabriela A1 - Andrade, Francisco J. A1 - Schöning, Michael Josef A1 - Wang, Joseph T1 - Epidermal tattoo potentiometric sodium sensors with wireless signal transduction for continuous non-invasive sweat monitoring JF - Biosensors and bioelectronics N2 - This article describes the fabrication, characterization and application of an epidermal temporary-transfer tattoo-based potentiometric sensor, coupled with a miniaturized wearable wireless transceiver, for real-time monitoring of sodium in the human perspiration. Sodium excreted during perspiration is an excellent marker for electrolyte imbalance and provides valuable information regarding an individual's physical and mental wellbeing. The realization of the new skin-worn non-invasive tattoo-like sensing device has been realized by amalgamating several state-of-the-art thick film, laser printing, solid-state potentiometry, fluidics and wireless technologies. The resulting tattoo-based potentiometric sodium sensor displays a rapid near-Nernstian response with negligible carryover effects, and good resiliency against various mechanical deformations experienced by the human epidermis. On-body testing of the tattoo sensor coupled to a wireless transceiver during exercise activity demonstrated its ability to continuously monitor sweat sodium dynamics. The real-time sweat sodium concentration was transmitted wirelessly via a body-worn transceiver from the sodium tattoo sensor to a notebook while the subjects perspired on a stationary cycle. The favorable analytical performance along with the wearable nature of the wireless transceiver makes the new epidermal potentiometric sensing system attractive for continuous monitoring the sodium dynamics in human perspiration during diverse activities relevant to the healthcare, fitness, military, healthcare and skin-care domains. Y1 - 2014 U6 - http://dx.doi.org/10.1016/j.bios.2013.11.039 SN - 1873-4235 (E-Journal); 0956-5663 (Print) VL - 54 SP - 603 EP - 609 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Miyamoto, Ko-ichiro A1 - Itabashi, Akinori A1 - Wagner, Torsten A1 - Schöning, Michael Josef A1 - Yoshinobu, Tatsuo T1 - High-speed chemical imaging inside a microfluidic channel JF - Sensors and actuators. B: Chemical N2 - In this study, a high-speed chemical imaging system was developed for visualization of the interior of a microfluidic channel. A microfluidic channel was constructed on the sensor surface of the light-addressable potentiometric sensor (LAPS), on which the ion concentrations could be measured in parallel at up to 64 points illuminated by optical fibers. The temporal change of pH distribution inside the microfluidic channel was recorded at a maximum rate of 100 frames per second (fps). The high frame rate allowed visualization of moving interfaces and plugs in the channel even at a flow velocity of 111 mm/s, which suggests the feasibility of plug-based microfluidic devices for flow-injection analysis (FIA). Y1 - 2014 U6 - http://dx.doi.org/10.1016/j.snb.2013.12.090 SN - 1873-3077 (E-Journal); 0925-4005 (Print) VL - 194 SP - 521 EP - 527 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Moseley, Fiona A1 - Halamek, Jan A1 - Kramer, Friederike A1 - Poghossian, Arshak A1 - Schöning, Michael Josef A1 - Katz, Evgeny T1 - An enzyme-based reversible CNOT logic gate realized in a flow system JF - Analyst N2 - An enzyme system organized in a flow device was used to mimic a reversible Controlled NOT (CNOT) gate with two input and two output signals. Reversible conversion of NAD⁺ and NADH cofactors was used to perform a XOR logic operation, while biocatalytic hydrolysis of p-nitrophenyl phosphate resulted in an Identity operation working in parallel. The first biomolecular realization of a CNOT gate is promising for integration into complex biomolecular networks and future biosensor/biomedical applications. Y1 - 2014 U6 - http://dx.doi.org/10.1039/C4AN00133H SN - 1364-5528 (E-Journal) ; 0003-2654 (Print) VL - 139 IS - 8 SP - 1839 EP - 1842 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Leinhos, Marcel A1 - Schusser, Sebastian A1 - Bäcker, Matthias A1 - Poghossian, Arshak A1 - Schöning, Michael Josef T1 - Micromachined multi-parameter sensor chip for the control of polymer-degradation medium JF - Physica Status Solidi (A) : special issue on engineering and functional interfaces N2 - It is well known that the degradation environment can strongly influence the biodegradability and kinetics of biodegradation processes of polymers. Therefore, besides the monitoring of the degradation process, it is also necessary to control the medium in which the degradation takes place. In this work, a micromachined multi-parameter sensor chip for the control of the polymer-degradation medium has been developed. The chip combines a capacitive field-effect pH sensor, a four-electrode electrolyte-conductivity sensor and a thin-film Pt-temperature sensor. The results of characterization of individual sensors are presented. In addition, the multi-parameter sensor chip together with an impedimetric polymer-degradation sensor was simultaneously characterized in degradation solutions with different pH and electrolyte conductivity. The obtained results demonstrate the feasibility of the multi-parameter sensor chip for the control of the polymer-degradation medium. Y1 - 2014 U6 - http://dx.doi.org/10.1002/pssa.201330364 SN - 1521-396X (E-Journal); 1862-6319 (E-Journal); 0031-8965 (Print); 1862-6300 (Print) VL - 211 IS - 6 SP - 1346 EP - 1351 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Huck, Christina A1 - Poghossian, Arshak A1 - Kerroumi, Iman A1 - Schusser, Sebastian A1 - Bäcker, Matthias A1 - Zander, Willi A1 - Schubert, Jürgen A1 - Buniatyan, Vahe V. A1 - Martirosyan, Norayr W. A1 - Wagner, Patrick A1 - Schöning, Michael Josef T1 - Multiparameter sensor chip with Barium Strontium Titanate as multipurpose material JF - Electroanalysis N2 - It is well known that biochemical and biotechnological processes are strongly dependent and affected by a variety of physico-chemical parameters such as pH value, temperature, pressure and electrolyte conductivity. Therefore, these quantities have to be monitored or controlled in order to guarantee a stable process operation, optimization and high yield. In this work, a sensor chip for the multiparameter detection of three physico-chemical parameters such as electrolyte conductivity, pH and temperature is realized using barium strontium titanate (BST) as multipurpose material. The chip integrates a capacitively coupled four-electrode electrolyte-conductivity sensor, a capacitive field-effect pH sensor and a thin-film Pt-temperature sensor. Due to the multifunctional properties of BST, it is utilized as final outermost coating layer of the processed sensor chip and serves as passivation and protection layer as well as pH-sensitive transducer material at the same time. The results of testing of the individual sensors of the developed multiparameter sensor chip are presented. In addition, a quasi-simultaneous multiparameter characterization of the sensor chip in buffer solutions with different pH value and electrolyte conductivity is performed. To study the sensor behavior and the suitability of BST as multifunctional material under harsh environmental conditions, the sensor chip was exemplarily tested in a biogas digestate. Y1 - 2014 U6 - http://dx.doi.org/10.1002/elan.201400076 SN - 1521-4109 (E-Journal); 1040-0397 (Print) VL - 26 IS - 5 SP - 980 EP - 987 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Bäcker, Matthias A1 - Kramer, F. A1 - Huck, Christina A1 - Poghossian, Arshak A1 - Bratov, A. A1 - Abramova, N. A1 - Schöning, Michael Josef T1 - Planar and 3D interdigitated electrodes for biosensing applications: The impact of a dielectric barrier on the sensor properties JF - Physica Status Solidi (A) - Applications and Materials Science N2 - Planar and three-dimensional (3D) interdigitated electrodes (IDE) with electrode digits separated by an insulating barrier of different heights were electrochemically characterized and compared in terms of their sensing properties. Due to the impact of the surface resistance, both types of IDE structures display a non-linear behavior in low-ionic strength solutions. The experimental data were fitted to an electrical equivalent circuit and interpreted taking into account the surface-charge-governed properties. The effect of a charged polyelectrolyte layer electrostatically assembled onto the sensor surface on the surface resistance in solutions with different KCl concentration is studied. In case of the same electrode footprint, 3D-IDEs show a larger cell constant and a higher sensitivity to molecular adsorption than that of planar IDEs. The obtained results demonstrate the potential of 3D-IDEs as a new transducer structure for a direct label-free sensing of charged molecules. Y1 - 2014 U6 - http://dx.doi.org/10.1002/pssa.201330416 SN - 1521-396X (E-Journal); 1862-6319 (E-Journal); 0031-8965 (Print); 1862-6300 (Print) VL - 211 IS - 6 SP - 1357 EP - 1363 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Huck, Christina A1 - Poghossian, Arshak A1 - Bäcker, Matthias A1 - Chaudhuri, S. A1 - Zander, W. A1 - Schubert, J. A1 - Begoyan, V. K. A1 - Buniatyan, V. V. A1 - Wagner, P. A1 - Schöning, Michael Josef T1 - Capacitively coupled electrolyte-conductivity sensor based on high-k material of barium strontium titanate JF - Sensors and actuators. B: Chemical Y1 - 2014 U6 - http://dx.doi.org/10.1016/j.snb.2014.02.103 SN - 1873-3077 (E-Journal); 0925-4005 (Print) IS - 198 SP - 102 EP - 109 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Takenaga, Shoko A1 - Biselli, Manfred A1 - Schnitzler, Thomas A1 - Öhlschläger, Peter A1 - Wagner, Torsten A1 - Schöning, Michael Josef T1 - Toward multi-analyte bioarray sensors: LAPS-based on-chip determination of a Michaelis–Menten-like kinetics for cell culturing JF - Physica status solidi A : Applications and materials science N2 - The metabolic activity of Chinese hamster ovary (CHO) cells was observed using a light-addressable potentiometric sensor (LAPS). The dependency toward different glucose concentrations (17–200 mM) follows a Michaelis–Menten kinetics trajectory with Kₘ = 32.8 mM, and the obtained Kₘ value in this experiment was compared with that found in literature. In addition, the pH shift induced by glucose metabolism of tumor cells transfected with the HPV-16 genome (C3 cells) was successfully observed. These results indicate the possibility to determine the tumor cells metabolism with a LAPS-based measurement device. Y1 - 2014 U6 - http://dx.doi.org/10.1002/pssa.201330464 SN - 1521-396X (E); 1862-6319 (E-Journal); 0031-8965 (Print); 1862-6300 (Print) VL - 211 IS - 6 SP - 1410 EP - 1415 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Wu, Chunsheng A1 - Bronder, Thomas A1 - Poghossian, Arshak A1 - Werner, Frederik A1 - Bäcker, Matthias A1 - Schöning, Michael Josef T1 - Label-free electrical detection of DNA with a multi-spot LAPS: First step towards light-addressable DNA chips JF - Physica status solidi A : Applications and materials science N2 - A multi-spot (4 × 4 spots) light-addressable potentiometric sensor (MLAPS) consisting of an Al–p-Si–SiO2 structure has been applied for the label-free electrical detection of DNA (deoxyribonucleic acid) immobilization and hybridization by the intrinsic molecular charge for the first time. Single-stranded probe ssDNA molecules (20 bases) were covalently immobilized onto the silanized SiO2 gate surface. The unspecific adsorption of mismatch ssDNA on the MLAPS gate surface was blocked by bovine serum albumin molecules. To reduce the screening effect and to achieve a high sensor signal, the measurements were performed in a low ionic-strength solution. The photocurrent–voltage (I–V) curves were simultaneously recorded on all 16 spots after each surface functionalization step. Large shifts of I–V curves of 25 mV were registered after the DNA immobilization and hybridization event. In contrast, a small potential shift (∼5 mV) was observed in case of mismatch ssDNA, revealing good specificity of the sensor. The obtained results demonstrate the potential of the MLAPS as promising transducer platform for the multi-spot label-free electrical detection of DNA molecules by their intrinsic molecular charge. Y1 - 2014 U6 - http://dx.doi.org/10.1002/pssa.201330442 SN - 1521-396X (E-Journal); 1862-6319 (E-Journal); 0031-8965 (Print); 1862-6300 (Print) VL - 211 IS - 6 SP - 1423 EP - 1428 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Guo, Yuanyuan A1 - Seki, Kosuke A1 - Miyamoto, Ko-ichiro A1 - Wagner, Torsten A1 - Schöning, Michael Josef A1 - Yoshinobu, Tatsuo T1 - Novel photoexcitation method for light-addressable potentiometric sensor with higher spatial resolution JF - Applied physics express : APEX N2 - A novel photoexcitation method for the light-addressable potentiometric sensor (LAPS) is proposed to achieve a higher spatial resolution of chemical images. The proposed method employs a combined light source that consists of a modulated light probe, which generates the alternating photocurrent signal, and a ring of constant illumination surrounding it. The constant illumination generates a sheath of carriers with increased concentration which suppresses the spread of photocarriers by enhanced recombination. A device simulation was carried out to verify the effect of constant illumination on the spatial resolution, which demonstrated that a higher spatial resolution can be obtained. Y1 - 2014 U6 - http://dx.doi.org/10.7567/APEX.7.067301 SN - 1882-0786 (E-Journa); 1882-0778 (Print) VL - 7 IS - 6 SP - 067301-4 PB - IOP CY - Bristol ER - TY - JOUR A1 - Wagner, Patrick A1 - Doll, Theodor A1 - Schöning, Michael Josef T1 - Engineering of functional interfaces / Patrick Wagner ; Theodor Doll ; Michael J. Schöning (eds.) JF - Physica status solidi (A) : Applications and materials science Y1 - 2014 U6 - http://dx.doi.org/10.1002/pssa.201470241 SN - 1521-396X (E-Book); 1862-6319 (E-Book); 0031-8965 (Print); 1862-6300 (Print) VL - 211 IS - 6 SP - 1339 EP - 1339 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Guo, Yuanyuan A1 - Miyamoto, Ko-ichiro A1 - Wagner, Torsten A1 - Schöning, Michael Josef A1 - Yoshinobu, Tatsuo T1 - Theoretical study and simulation of light-addressable potentiometric sensors JF - Physica status solidi (A) : applications and materials N2 - The light-addressable potentiometric sensor (LAPS) is a semiconductor-based potentiometric sensor using a light probe with an ability of detecting the concentration of biochemical species in a spatially resolved manner. As an important biomedical sensor, research has been conducted to improve its performance, for instance, to realize high-speed measurement. In this work, the idea of facilitating the device-level simulation, instead of using an equivalent-circuit model, is presented for detailed analysis and optimization of the performance of the LAPS. Both carrier distribution and photocurrent response have been simulated to provide new insight into both amplitude-mode and phase-mode operations of the LAPS. Various device parameters can be examined to effectively design and optimize the LAPS structures and setups for enhanced performance. Y1 - 2014 U6 - http://dx.doi.org/10.1002/pssa.201330354 SN - 0031-8965 VL - 211 IS - 6 SP - 1467 EP - 1472 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Riedel, Marc A1 - Kartchemnik, Julia A1 - Schöning, Michael Josef A1 - Lisdat, Fred T1 - Impedimetric DNA detection – steps forward to sensorial application JF - Analytical chemistry N2 - This study describes a label-free impedimetric sensor based on short ssDNA recognition elements for the detection of hybridization events. We concentrate on the elucidation of the influence of target length and recognition sequence position on the sensorial performance. The impedimetric measurements are performed in the presence of the redox system ferri-/ferrocyanide and show an increase in charge transfer resistance upon hybridization of ssDNA to the sensor surface. Investigations on the impedimetric signal stability demonstrate a clear influence of the buffers used during the sensor preparation and the choice of the passivating mercaptoalcanol compound. A stable sensor system has been developed, enabling a reproducible detection of 25mer target DNA in the low nanomolar range. After hybridization, a sensor regeneration can be reached with deionized water by adjustment of effective convection conditions, ensuring a sensor reusability. By investigations of longer targets with overhangs exposed to the solution, we can demonstrate applicability of the impedimetric detection for longer ssDNA. However, a decreasing charge transfer resistance change (ΔRct) is found by extending the overhang. As a strategy to increase the impedance change for longer target strands, the position of the recognition sequence can be designed in a way that a small overhang is exposed to the electrode surface. This is found to result in an increase in the relative Rct change. These results suggest that DNA and consequently negative charge near the electrode possess a larger impact on the impedimetric signal than DNA further away. Y1 - 2014 U6 - http://dx.doi.org/10.1021/ac501800q SN - 1520-6882 (E-Journal); 0003-2700 (Print); 0096-4484 (Print) VL - 86 (2014) IS - 15 SP - 7867 EP - 7874 PB - ACS Publications CY - Columbus ER - TY - JOUR A1 - Guo, Yuanyuan A1 - Miyamoto, Ko-ichiro A1 - Wagner, Torsten A1 - Schöning, Michael Josef A1 - Yoshinobu, Tatsuo T1 - Device simulation of the light-addressable potentiometric sensor for the investigation of the spatial resolution JF - Sensors and actuators B: Chemical N2 - As a semiconductor-based electrochemical sensor, the light-addressable potentiometric sensor (LAPS) can realize two dimensional visualization of (bio-)chemical reactions at the sensor surface addressed by localized illumination. Thanks to this imaging capability, various applications in biochemical and biomedical fields are expected, for which the spatial resolution is critically significant. In this study, therefore, the spatial resolution of the LAPS was investigated in detail based on the device simulation. By calculating the spatiotemporal change of the distributions of electrons and holes inside the semiconductor layer in response to a modulated illumination, the photocurrent response as well as the spatial resolution was obtained as a function of various parameters such as the thickness of the Si substrate, the doping concentration, the wavelength and the intensity of illumination. The simulation results verified that both thinning the semiconductor substrate and increasing the doping concentration could improve the spatial resolution, which were in good agreement with known experimental results and theoretical analysis. More importantly, new findings of interests were also obtained. As for the dependence on the wavelength of illumination, it was found that the known dependence was not always the case. When the Si substrate was thick, a longer wavelength resulted in a higher spatial resolution which was known by experiments. When the Si substrate was thin, however, a longer wavelength of light resulted in a lower spatial resolution. This finding was explained as an effect of raised concentration of carriers, which reduced the thickness of the space charge region. The device simulation was found to be helpful to understand the relationship between the spatial resolution and device parameters, to understand the physics behind it, and to optimize the device structure and measurement conditions for realizing higher performance of chemical imaging systems. Y1 - 2014 U6 - http://dx.doi.org/10.1016/j.snb.2014.08.016 SN - 1873-3077 (E-Journal); 0925-4005 (Print) VL - 204 SP - 659 EP - 665 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Khaydukova, M. M. A1 - Zadorozhnaya, O. A. A1 - Kirsanov, D. O. A1 - Iken, Heiko A1 - Rolka, David A1 - Schöning, Michael Josef A1 - Babain, V. A. A1 - Vlasov, Yu. G. A1 - Legin, A. V. T1 - Multivariate processing of atomic-force microscopy images for detection of the response of plasticized polymeric membranes JF - Russian journal of applied chemistry N2 - The possibility of using the atomic-force microscopy as a method for detection of the analytical signal from plasticized polymeric sensor membranes was analyzed. The surfaces of cadmium-selective membranes based on two polymeric matrices were examined. The digital images were processed with multivariate image analysis techniques. A correlation was found between the surface profile of an ion-selective membrane and the concentration of the ion in solution. Y1 - 2014 U6 - http://dx.doi.org/10.1134/S1070427214030112 SN - 1608-3296 (E-Journal); 1070-4272 (Print) VL - 87 IS - 3 SP - 307 EP - 314 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Bäcker, Matthias A1 - Schusser, Sebastian A1 - Poghossian, Arshak A1 - Schöning, Michael Josef T1 - Multi-Parametererfassung mit siliziumbasiertem Sensorchip: Aus Drei mach Eins JF - GIT Labor-Fachzeitschrift Y1 - 2014 SN - 0016-3538 IS - 2 SP - 28 EP - 30 PB - Wiley ER - TY - JOUR A1 - Murib, Mohammed Sharif A1 - Yeap, Weng-Siang A1 - Martens, Daan A1 - Bienstman, Peter A1 - Ceuninck, Ward de A1 - Grinsven, Bart van A1 - Schöning, Michael Josef A1 - Michiels, Luc A1 - Haenen, Ken A1 - Ameloot, Marcel A1 - Serpengüzel, Ali A1 - Wagner, Patrick T1 - Photonic detection and characterization of DNA using sapphire microspheres JF - Journal of biomedical optics N2 - A microcavity-based deoxyribonucleic acid (DNA) optical biosensor is demonstrated for the first time using synthetic sapphire for the optical cavity. Transmitted and elastic scattering intensity at 1510 nm are analyzed from a sapphire microsphere (radius 500  μm, refractive index 1.77) on an optical fiber half coupler. The 0.43 nm angular mode spacing of the resonances correlates well with the optical size of the sapphire sphere. Probe DNA consisting of a 36-mer fragment was covalently immobilized on a sapphire microsphere and hybridized with a 29-mer target DNA. Whispering gallery modes (WGMs) were monitored before the sapphire was functionalized with DNA and after it was functionalized with single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). The shift in WGMs from the surface modification with DNA was measured and correlated well with the estimated thickness of the add-on DNA layer. It is shown that ssDNA is more uniformly oriented on the sapphire surface than dsDNA. In addition, it is shown that functionalization of the sapphire spherical surface with DNA does not affect the quality factor (Q≈104) of the sapphire microspheres. The use of sapphire is especially interesting because this material is chemically resilient, biocompatible, and widely used for medical implants. Y1 - 2014 U6 - http://dx.doi.org/10.1117/1.JBO.19.9.097006 SN - 1560-2281 (E-Journal); 1083-3668 (Print) VL - 19 IS - 9 SP - 097006 PB - SPIE CY - Bellingham ER -