@article{HuckSchiffelsHerreraetal.2013, author = {Huck, Christina and Schiffels, Johannes and Herrera, Cony N. and Schelden, Maximilian and Selmer, Thorsten and Poghossian, Arshak and Baumann, Marcus and Wagner, Patrick and Sch{\"o}ning, Michael Josef}, title = {Metabolic responses of Escherichia coli upon glucose pulses captured by a capacitive field-effect sensor}, series = {Physica Status Solidi (A)}, volume = {210}, journal = {Physica Status Solidi (A)}, number = {5}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0031-8965}, doi = {10.1002/pssa.201200900}, pages = {926 -- 931}, year = {2013}, abstract = {Living cells are complex biological systems transforming metabolites taken up from the surrounding medium. Monitoring the responses of such cells to certain substrate concentrations is a challenging task and offers possibilities to gain insight into the vitality of a community influenced by the growth environment. Cell-based sensors represent a promising platform for monitoring the metabolic activity and thus, the "welfare" of relevant organisms. In the present study, metabolic responses of the model bacterium Escherichia coli in suspension, layered onto a capacitive field-effect structure, were examined to pulses of glucose in the concentration range between 0.05 and 2 mM. It was found that acidification of the surrounding medium takes place immediately after glucose addition and follows Michaelis-Menten kinetic behavior as a function of the glucose concentration. In future, the presented setup can, therefore, be used to study substrate specificities on the enzymatic level and may as well be used to perform investigations of more complex metabolic responses. Conclusions and perspectives highlighting this system are discussed.}, language = {en} } @article{SchusserKrischerBaeckeretal.2015, author = {Schusser, Sebastian and Krischer, Maximillian and B{\"a}cker, Matthias and Poghossian, Arshak and Wagner, Patrick and Sch{\"o}ning, Michael Josef}, title = {Monitoring of the Enzymatically Catalyzed Degradation of Biodegradable Polymers by Means of Capacitive Field-Effect Sensors}, series = {Analytical Chemistry}, volume = {87}, journal = {Analytical Chemistry}, number = {13}, publisher = {ACS Publications}, address = {Washington, DC}, issn = {1520-6882}, doi = {10.1021/acs.analchem.5b00617}, pages = {6607 -- 6613}, year = {2015}, abstract = {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.}, language = {en} } @article{ReisertSchneiderGeissleretal.2013, author = {Reisert, Steffen and Schneider, Benno and Geissler, Hanno and Gompel, Matthias van and Wagner, Patrick and Sch{\"o}ning, Michael Josef}, title = {Multi-sensor chip for the investigation of different types of metal oxides for the detection of H2O2 in the ppm range}, series = {physica status solidi (a)}, volume = {210}, journal = {physica status solidi (a)}, number = {5}, publisher = {Wiley}, address = {Weinheim}, issn = {1862-6319}, pages = {898 -- 904}, year = {2013}, abstract = {In this work, a multi-sensor chip for the investigation of the sensing properties of different types of metal oxides towards hydrogen peroxide in the ppm range is presented. The fabrication process and physical characterization of the multi-sensor chip are described. Pure SnO2 and WO3 as well as Pd- and Pt-doped SnO2 films are characterized in terms of their sensitivity to H2O2. The sensing films have been prepared by drop-coating of water-dispensed nano-powders. A physical characterization, including scanning electron microscopy and X-ray diffraction analysis of the deposited metal-oxide films, was done. From the measurements in hydrogen peroxide atmosphere, it could be shown, that all of the tested metal oxide films are suitable for the detection of H2O2 in the ppm range. The highest sensitivity and reproducibility was achieved using Pt-doped SnO2. Calibration plot of a SnO2, WO3, Pt-, and Pd-doped SnO2 gas sensor for H2O2 concentrations in the ppm range.}, language = {en} } @article{HuckPoghossianKerroumietal.2014, author = {Huck, Christina and Poghossian, Arshak and Kerroumi, Iman and Schusser, Sebastian and B{\"a}cker, Matthias and Zander, Willi and Schubert, J{\"u}rgen and Buniatyan, Vahe V. and Martirosyan, Norayr W. and Wagner, Patrick and Sch{\"o}ning, Michael Josef}, title = {Multiparameter sensor chip with Barium Strontium Titanate as multipurpose material}, series = {Electroanalysis}, volume = {26}, journal = {Electroanalysis}, number = {5}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1521-4109 (E-Journal); 1040-0397 (Print)}, doi = {10.1002/elan.201400076}, pages = {980 -- 987}, year = {2014}, abstract = {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.}, language = {en} } @article{KarschuckSchmidtAchtsnichtetal.2023, author = {Karschuck, Tobias and Schmidt, Stefan and Achtsnicht, Stefan and Poghossian, Arshak and Wagner, Patrick and Sch{\"o}ning, Michael Josef}, title = {Multiplexing system for automated characterization of a capacitive field-effect sensor array}, series = {Physica Status Solidi A}, volume = {220}, journal = {Physica Status Solidi A}, number = {22}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1862-6300 (Print)}, doi = {10.1002/pssa.202300265}, pages = {7 Seiten}, year = {2023}, abstract = {In comparison to single-analyte devices, multiplexed systems for a multianalyte detection offer a reduced assay time and sample volume, low cost, and high throughput. Herein, a multiplexing platform for an automated quasi-simultaneous characterization of multiple (up to 16) capacitive field-effect sensors by the capacitive-voltage (C-V) and the constant-capacitance (ConCap) mode is presented. The sensors are mounted in a newly designed multicell arrangement with one common reference electrode and are electrically connected to the impedance analyzer via the base station. A Python script for the automated characterization of the sensors executes the user-defined measurement protocol. The developed multiplexing system is tested for pH measurements and the label-free detection of ligand-stabilized, charged gold nanoparticles.}, language = {en} } @article{HuckJollyWagneretal.2011, author = {Huck, Christina and Jolly, Christina and Wagner, Patrick and Poghossian, Arshak and Sch{\"o}ning, Michael Josef}, title = {One-chip integrated dual amperometric/field-effect sensor for the detection of dissolved hydrogen}, series = {Procedia Engineering. 25 (2011)}, journal = {Procedia Engineering. 25 (2011)}, publisher = {Elsevier}, address = {Amsterdam}, isbn = {1877-7058}, pages = {1161 -- 1164}, year = {2011}, language = {en} } @article{DantismRoehlenWagneretal.2018, author = {Dantism, Shahriar and R{\"o}hlen, Desiree and Wagner, Torsten and Wagner, Patrick and Sch{\"o}ning, Michael Josef}, title = {Optimization of Cell-Based Multi-Chamber LAPS Measurements Utilizing FPGA-Controlled Laser-Diode Modules}, series = {physica status solidi a : applications and materials sciences}, volume = {215}, journal = {physica status solidi a : applications and materials sciences}, number = {15}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1862-6319}, doi = {10.1002/pssa.201800058}, pages = {Article number 1800058}, year = {2018}, abstract = {A light-addressable potentiometric sensor (LAPS) is a field-effect-based potentiometric device, which detects concentration changes of an analyte solution on the sensor surface in a spatially resolved way. It uses a light source to generate electron-hole pairs inside the semiconductor, which are separated in the depletion region due to an applied bias voltage across the sensor structure and hence, a surface-potential-dependent photocurrent can be read out. However, depending on the beam angle of the light source, scattering effects can occur, which influence the recorded signal in LAPS-based differential measurements. To solve this problem, a novel illumination unit based on a field programmable gate array (FPGA) consisting of 16 small-sized tunable infrared laser-diode modules (LDMs) is developed. Due to the improved focus of the LDMs with a beam angle of only 2 mrad, undesirable scattering effects are minimized. Escherichia coli (E. coli) K12 bacteria are used as a test microorganism to study the extracellular acidification on the sensor surface. Furthermore, a salt bridge chamber is built up and integrated with the LAPS system enabling multi-chamber differential measurements with a single Ag/AgCl reference electrode.}, language = {en} } @article{AbouzarPoghossianRazavietal.2008, author = {Abouzar, Maryam H. and Poghossian, Arshak and Razavi, Arash and Besmehn, Astrid and Bijnens, Nathalie and Williams, Oliver A. and Haenen, Ken and Wagner, Patrick and Sch{\"o}ning, Michael Josef}, title = {Penicillin detection with nanocrystalline-diamond field-effect sensor}, series = {physica status solidi (a). 205 (2008), H. 9}, journal = {physica status solidi (a). 205 (2008), H. 9}, isbn = {1862-6319}, pages = {2141 -- 2145}, year = {2008}, language = {en} } @article{MuribYeapMartensetal.2014, author = {Murib, Mohammed Sharif and Yeap, Weng-Siang and Martens, Daan and Bienstman, Peter and Ceuninck, Ward de and Grinsven, Bart van and Sch{\"o}ning, Michael Josef and Michiels, Luc and Haenen, Ken and Ameloot, Marcel and Serpeng{\"u}zel, Ali and Wagner, Patrick}, title = {Photonic detection and characterization of DNA using sapphire microspheres}, series = {Journal of biomedical optics}, volume = {19}, journal = {Journal of biomedical optics}, number = {9}, publisher = {SPIE}, address = {Bellingham}, issn = {1560-2281 (E-Journal); 1083-3668 (Print)}, doi = {10.1117/1.JBO.19.9.097006}, pages = {097006}, year = {2014}, abstract = {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.}, language = {en} } @article{MuribYeapMartensetal.2015, author = {Murib, M. S. and Yeap, W. S. and Martens, D. and Liu, X. and Bienstman, P. and Fahlman, M. and Sch{\"o}ning, Michael Josef and Michiels, L. and Haenen, K. and Serpeng{\"u}zel, A. and Wagner, Patrick}, title = {Photonic studies on polymer-coated sapphire-spheres : a model system for biological ligands}, series = {Sensors and actuators A: Physical}, volume = {222}, journal = {Sensors and actuators A: Physical}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-3069 (E-Journal); 0924-4247 (Print)}, doi = {10.1016/j.sna.2014.11.024}, pages = {212 -- 219}, year = {2015}, abstract = {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.}, language = {en} }