TY  - JOUR
A1  - Haeger, Gerrit
A1  - Bongaerts, Johannes
A1  - Siegert, Petra
T1  - A convenient ninhydrin assay in 96-well format for amino acid-releasing enzymes using an air-stable reagent
JF  - Analytical Biochemistry
N2  - An improved and convenient ninhydrin assay for aminoacylase activity measurements was developed using the commercial EZ Nin™ reagent. Alternative reagents from literature were also evaluated and compared. The addition of DMSO to the reagent enhanced the solubility of Ruhemann's purple (RP). Furthermore, we found that the use of a basic, aqueous buffer enhances stability of RP. An acidic protocol for the quantification of lysine was developed by addition of glacial acetic acid. The assay allows for parallel processing in a 96-well format with measurements microtiter plates.
Y1  - 2022
U6  - http://dx.doi.org/10.1016/j.ab.2022.114819
SN  - 1096-0309
IS  - 624
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Welden, Melanie
A1  - Severins, Robin
A1  - Poghossian, Arshak
A1  - Wege, Christina
A1  - Bongaerts, Johannes
A1  - Siegert, Petra
A1  - Keusgen, Michael
A1  - Schöning, Michael Josef
T1  - Detection of acetoin and diacetyl by a tobacco mosaic virus-assisted field-effect biosensor
JF  - Chemosensors
N2  - Acetoin and diacetyl have a major impact on the flavor of alcoholic beverages such as wine or beer. Therefore, their measurement is important during the fermentation process. Until now, gas chromatographic techniques have typically been applied; however, these require expensive laboratory equipment and trained staff, and do not allow for online monitoring. In this work, a capacitive electrolyte–insulator–semiconductor sensor modified with tobacco mosaic virus (TMV) particles as enzyme nanocarriers for the detection of acetoin and diacetyl is presented. The enzyme acetoin reductase from Alkalihalobacillus clausii DSM 8716ᵀ is immobilized via biotin–streptavidin affinity, binding to the surface of the TMV particles. The TMV-assisted biosensor is electrochemically characterized by means of leakage–current, capacitance–voltage, and constant capacitance measurements. In this paper, the novel biosensor is studied regarding its sensitivity and long-term stability in buffer solution. Moreover, the TMV-assisted capacitive field-effect sensor is applied for the detection of diacetyl for the first time. The measurement of acetoin and diacetyl with the same sensor setup is demonstrated. Finally, the successive detection of acetoin and diacetyl in buffer and in diluted beer is studied by tuning the sensitivity of the biosensor using the pH value of the measurement solution.
Y1  - 2022
U6  - http://dx.doi.org/10.3390/chemosensors10060218
SN  - 2227-9040
N1  - This article belongs to the Special Issue "Nanostructured Devices for Biochemical Sensing"
VL  - 10
IS  - 6
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Welden, Melanie
A1  - Poghossian, Arshak
A1  - Vahidpour, Farnoosh
A1  - Wendlandt, Tim
A1  - Keusgen, Michael
A1  - Wege, Christina
A1  - Schöning, Michael Josef
T1  - Towards multi-analyte detection with field-effect capacitors modified with tobacco mosaic virus bioparticles as enzyme nanocarriers
JF  - Biosensors
N2  - Utilizing an appropriate enzyme immobilization strategy is crucial for designing enzyme-based biosensors. Plant virus-like particles represent ideal nanoscaffolds for an extremely dense and precise immobilization of enzymes, due to their regular shape, high surface-to-volume ratio and high density of surface binding sites. In the present work, tobacco mosaic virus (TMV) particles were applied for the co-immobilization of penicillinase and urease onto the gate surface of a field-effect electrolyte-insulator-semiconductor capacitor (EISCAP) with a p-Si-SiO₂-Ta₂O₅ layer structure for the sequential detection of penicillin and urea. The TMV-assisted bi-enzyme EISCAP biosensor exhibited a high urea and penicillin sensitivity of 54 and 85 mV/dec, respectively, in the concentration range of 0.1–3 mM. For comparison, the characteristics of single-enzyme EISCAP biosensors modified with TMV particles immobilized with either penicillinase or urease were also investigated. The surface morphology of the TMV-modified Ta₂O₅-gate was analyzed by scanning electron microscopy. Additionally, the bi-enzyme EISCAP was applied to mimic an XOR (Exclusive OR) enzyme logic gate.
KW  - urease
KW  - enzyme-logic gate
KW  - bi-enzyme biosensor
KW  - capacitive field-effect sensor
KW  - tobacco mosaic virus (TMV)
KW  - penicillinase
Y1  - 2022
U6  - http://dx.doi.org/10.3390/bios12010043
SN  - 2079-6374
N1  - This article belongs to the Special Issue "Biosensors: 10th Anniversary Feature Papers"
VL  - 12
IS  - 1
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Molinnus, Denise
A1  - Janus, Kevin Alexander
A1  - Fang, Anyelina C.
A1  - Drinic, Aleksander
A1  - Achtsnicht, Stefan
A1  - Köpf, Marius
A1  - Keusgen, Michael
A1  - Schöning, Michael Josef
T1  - Thick-film carbon electrode deposited onto a biodegradable fibroin substrate for biosensing applications
JF  - Physica status solidi (a)
N2  - This study addresses a proof-of-concept experiment with a biocompatible screen-printed carbon electrode deposited onto a biocompatible and biodegradable substrate, which is made of fibroin, a protein derived from silk of the Bombyx mori silkworm. To demonstrate the sensor performance, the carbon electrode is functionalized as a glucose biosensor with the enzyme glucose oxidase and encapsulated with a silicone rubber to ensure biocompatibility of the contact wires. The carbon electrode is fabricated by means of thick-film technology including a curing step to solidify the carbon paste. The influence of the curing temperature and curing time on the electrode morphology is analyzed via scanning electron microscopy. The electrochemical characterization of the glucose biosensor is performed by amperometric/voltammetric measurements of different glucose concentrations in phosphate buffer. Herein, systematic studies at applied potentials from 500 to 1200 mV to the carbon working electrode (vs the Ag/AgCl reference electrode) allow to determine the optimal working potential. Additionally, the influence of the curing parameters on the glucose sensitivity is examined over a time period of up to 361 days. The sensor shows a negligible cross-sensitivity toward ascorbic acid, noradrenaline, and adrenaline. The developed biocompatible biosensor is highly promising for future in vivo and epidermal applications.
KW  - biocompatible materials
KW  - biodegradable electronic devices
KW  - biosensors
KW  - carbon electrodes
KW  - glucose
Y1  - 2022
U6  - http://dx.doi.org/10.1002/pssa.202200100
SN  - 1862-6319
N1  - Corresponding author: Michael J. Schöning
VL  - 219
IS  - 23
SP  - 1
EP  - 9
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Molinnus, Denise
A1  - Iken, Heiko
A1  - Johnen, Anna Lynn
A1  - Richstein, Benjamin
A1  - Hellmich, Lena
A1  - Poghossian, Arshak
A1  - Knoch, Joachim
A1  - Schöning, Michael Josef
T1  - Miniaturized pH-Sensitive Field-Effect Capacitors with Ultrathin Ta₂O₅ Films Prepared by Atomic Layer Deposition
JF  - physica status solidi (a) applications and materials science
N2  - Miniaturized electrolyte–insulator–semiconductor capacitors (EISCAPs) with ultrathin gate insulators have been studied in terms of their pH-sensitive sensor characteristics: three different EISCAP systems consisting of Al–p-Si–Ta2O5(5 nm), Al–p-Si–Si3N4(1 or 2 nm)–Ta2O5 (5 nm), and Al–p-Si–SiO2(3.6 nm)–Ta2O5(5 nm) layer structures are characterized in buffer solution with different pH values by means of capacitance–voltage and constant capacitance method. The SiO2 and Si3N4 gate insulators are deposited by rapid thermal oxidation and rapid thermal nitridation, respectively, whereas the Ta2O5 film is prepared by atomic layer deposition. All EISCAP systems have a clear pH response, favoring the stacked gate insulators SiO2–Ta2O5 when considering the overall sensor characteristics, while the Si3N4(1 nm)–Ta2O5 stack delivers the largest accumulation capacitance (due to the lower equivalent oxide thickness) and a higher steepness in the slope of the capacitance–voltage curve among the studied stacked gate insulator systems.
KW  - atomic layer deposition
KW  - capacitive field-effect sensors
KW  - pH sensors
KW  - ultrathin gate insulators
Y1  - 2022
U6  - http://dx.doi.org/10.1002/pssa.202100660
SN  - 1862-6319
VL  - 219
IS  - 8
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Poghossian, Arshak
A1  - Karschuck, Tobias
A1  - Wagner, Patrick
A1  - Schöning, Michael Josef
T1  - Field-Effect Capacitors Decorated with Ligand-Stabilized Gold Nanoparticles: Modeling and Experiments
JF  - Biosensors
N2  - Nanoparticles are recognized as highly attractive tunable materials for designing field-effect biosensors with enhanced performance. In this work, we present a theoretical model for electrolyte-insulator-semiconductor capacitors (EISCAP) decorated with ligand-stabilized charged gold nanoparticles. The charged AuNPs are taken into account as additional, nanometer-sized local gates. The capacitance-voltage (C–V) curves and constant-capacitance (ConCap) signals of the AuNP-decorated EISCAPs have been simulated. The impact of the AuNP coverage on the shift of the C–V curves and the ConCap signals was also studied experimentally on Al–p-Si–SiO₂ EISCAPs decorated with positively charged aminooctanethiol-capped AuNPs. In addition, the surface of the EISCAPs, modified with AuNPs, was characterized by scanning electron microscopy for different immobilization times of the nanoparticles.
KW  - aminooctanethiol
KW  - nanoparticle coverage
KW  - capacitive model
KW  - gold nanoparticles
KW  - field-effect sensor
KW  - electrolyte-insulator-semiconductor capacitors
Y1  - 2022
U6  - http://dx.doi.org/10.3390/bios12050334
SN  - 2079-6374
N1  - This article belongs to the Special Issue "Biosensors in Nanotechnology"
VL  - 12
IS  - 5
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Pourshahidi, Ali Mohammad
A1  - Achtsnicht, Stefan
A1  - Offenhäusser, Andreas
A1  - Krause, Hans-Joachim
ED  - Offenhäusser, Andreas
T1  - Frequency Mixing Magnetic Detection Setup Employing Permanent Ring Magnets as a Static Offset Field Source
JF  - Sensors
N2  - Frequency mixing magnetic detection (FMMD) has been explored for its applications in fields of magnetic biosensing, multiplex detection of magnetic nanoparticles (MNP) and the determination of core size distribution of MNP samples. Such applications rely on the application of a static offset magnetic field, which is generated traditionally with an electromagnet. Such a setup requires a current source, as well as passive or active cooling strategies, which directly sets a limitation based on the portability aspect that is desired for point of care (POC) monitoring applications. In this work, a measurement head is introduced that involves the utilization of two ring-shaped permanent magnets to generate a static offset magnetic field. A steel cylinder in the ring bores homogenizes the field. By variation of the distance between the ring magnets and of the thickness of the steel cylinder, the magnitude of the magnetic field at the sample position can be adjusted. Furthermore, the measurement setup is compared to the electromagnet offset module based on measured signals and temperature behavior.
KW  - magnetic sensors
KW  - biosensors
KW  - frequency mixing magnetic detection
KW  - magnetic nanoparticles
Y1  - 2022
U6  - http://dx.doi.org/10.3390/s22228776
SN  - 1424-8220
VL  - 22
IS  - 22
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Vahidpour, Farnoosh
A1  - Guthman, Eric
A1  - Arreola, Julia
A1  - Alghazali, Yousef H. M.
A1  - Wagner, Torsten
A1  - Schöning, Michael Josef
T1  - Assessment of Various Process Parameters for Optimized Sterilization Conditions Using a Multi-Sensing Platform
JF  - Foods
N2  - In this study, an online multi-sensing platform was engineered to simultaneously evaluate various process parameters of food package sterilization using gaseous hydrogen peroxide (H₂O₂). The platform enabled the validation of critical aseptic parameters. In parallel, one series of microbiological count reduction tests was performed using highly resistant spores of B. atrophaeus DSM 675 to act as the reference method for sterility validation. By means of the multi-sensing platform together with microbiological tests, we examined sterilization process parameters to define the most effective conditions with regards to the highest spore kill rate necessary for aseptic packaging. As these parameters are mutually associated, a correlation between different factors was elaborated. The resulting correlation indicated the need for specific conditions regarding the applied H₂O₂ gas temperature, the gas flow and concentration, the relative humidity and the exposure time. Finally, the novel multi-sensing platform together with the mobile electronic readout setup allowed for the online and on-site monitoring of the sterilization process, selecting the best conditions for sterility and, at the same time, reducing the use of the time-consuming and costly microbiological tests that are currently used in the food package industry.
KW  - spore kill rate
KW  - sterility
KW  - aseptic parameters
KW  - multi-sensing platform
KW  - gaseous hydrogen peroxide
Y1  - 2022
U6  - http://dx.doi.org/10.3390/foods11050660
SN  - 2304-8158
N1  - This article belongs to the Special Issue "Sensors and Biosensors Application for Food Industries"
VL  - 11
IS  - 5
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Vahidpour, Farnoosh
A1  - Alghazali, Yousef
A1  - Akca, Sevilay
A1  - Hommes, Gregor
A1  - Schöning, Michael Josef
T1  - An Enzyme-Based Interdigitated Electrode-Type Biosensor for Detecting Low Concentrations of H₂O₂ Vapor/Aerosol
JF  - Chemosensors
N2  - This work introduces a novel method for the detection of H₂O₂ vapor/aerosol of low concentrations, which is mainly applied in the sterilization of equipment in medical industry. Interdigitated electrode (IDE) structures have been fabricated by means of microfabrication techniques. A differential setup of IDEs was prepared, containing an active sensor element (active IDE) and a passive sensor element (passive IDE), where the former was immobilized with an enzymatic membrane of horseradish peroxidase that is selective towards H₂O₂. Changes in the IDEs’ capacitance values (active sensor element versus passive sensor element) under H₂O₂ vapor/aerosol atmosphere proved the detection in the concentration range up to 630 ppm with a fast response time (<60 s). The influence of relative humidity was also tested with regard to the sensor signal, showing no cross-sensitivity. The repeatability assessment of the IDE biosensors confirmed their stable capacitive signal in eight subsequent cycles of exposure to H₂O₂ vapor/aerosol. Room-temperature detection of H₂O₂ vapor/aerosol with such miniaturized biosensors will allow a future three-dimensional, flexible mapping of aseptic chambers and help to evaluate sterilization assurance in medical industry.
Y1  - 2022
U6  - http://dx.doi.org/10.3390/chemosensors10060202
SN  - 2227-9040
N1  - This article belongs to the Special Issue "Bioinspired Chemical Sensors and Micro-Nano Devices"
VL  - 10
IS  - 6
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Welden, Rene
A1  - Jablonski, Melanie
A1  - Wege, Christina
A1  - Keusgen, Michael
A1  - Wagner, Patrick Hermann
A1  - Wagner, Torsten
A1  - Schöning, Michael Josef
T1  - Light-Addressable Actuator-Sensor Platform for Monitoring and Manipulation of pH Gradients in Microfluidics: A Case Study with the Enzyme Penicillinase
JF  - Biosensors
N2  - The feasibility of light-addressed detection and manipulation of pH gradients inside an electrochemical microfluidic cell was studied. Local pH changes, induced by a light-addressable electrode (LAE), were detected using a light-addressable potentiometric sensor (LAPS) with different measurement modes representing an actuator-sensor system. Biosensor functionality was examined depending on locally induced pH gradients with the help of the model enzyme penicillinase, which had been immobilized in the microfluidic channel. The surface morphology of the LAE and enzyme-functionalized LAPS was studied by scanning electron microscopy. Furthermore, the penicillin sensitivity of the LAPS inside the microfluidic channel was determined with regard to the analyte’s pH influence on the enzymatic reaction rate. In a final experiment, the LAE-controlled pH inhibition of the enzyme activity was monitored by the LAPS.
KW  - microfluidics
KW  - enzyme kinetics
KW  - actuator-sensor system
KW  - light-addressable electrode
KW  - light-addressable potentiometric sensor
Y1  - 2021
U6  - http://dx.doi.org/10.3390/bios11060171
SN  - 2079-6374
N1  - This article belongs to the Special Issue "Selected Papers from the 1st International Electronic Conference on Biosensors (IECB 2020)"
VL  - 11
IS  - 6
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Poghossian, Arshak
A1  - Schöning, Michael Josef
T1  - Recent progress in silicon-based biologically sensitive field-effect devices
JF  - Current Opinion in Electrochemistry
N2  - Biologically sensitive field-effect devices (BioFEDs) advantageously combine the electronic field-effect functionality with the (bio)chemical receptor’s recognition ability for (bio)chemical sensing. In this review, basic and widely applied device concepts of silicon-based BioFEDs (ion-sensitive field-effect transistor, silicon nanowire transistor, electrolyte-insulator-semiconductor capacitor, light-addressable potentiometric sensor) are presented and recent progress (from 2019 to early 2021) is discussed. One of the main advantages of BioFEDs is the label-free sensing principle enabling to detect a large variety of biomolecules and bioparticles by their intrinsic charge. The review encompasses applications of BioFEDs for the label-free electrical detection of clinically relevant protein biomarkers, deoxyribonucleic acid molecules and viruses, enzyme-substrate reactions as well as recording of the cell acidification rate (as an indicator of cellular metabolism) and the extracellular potential.
Y1  - 2021
U6  - http://dx.doi.org/10.1016/j.coelec.2021.100811
SN  - 2451-9103
IS  - Article number: 100811
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Jildeh, Zaid B.
A1  - Wagner, Patrick H.
A1  - Schöning, Michael Josef
T1  - Sterilization of Objects, Products, and Packaging Surfaces and Their Characterization in Different Fields of Industry: The Status in 2020
JF  - physica status solidi (a) applications and materials science
N2  - The treatment method to deactivate viable microorganisms from objects or products is termed sterilization. There are multiple forms of sterilization, each intended to be applied for a specific target, which depends on—but not limited to—the thermal, physical, and chemical stability of that target. Herein, an overview on the currently used sterilization processes in the global market is provided. Different sterilization techniques are grouped under a category that describes the method of treatment: radiation (gamma, electron beam, X-ray, and ultraviolet), thermal (dry and moist heat), and chemical (ethylene oxide, ozone, chlorine dioxide, and hydrogen peroxide). For each sterilization process, the typical process parameters as defined by regulations and the mode of antimicrobial activity are summarized. Finally, the recommended microorganisms that are used as biological indicators to validate sterilization processes in accordance with the rules that are established by various regulatory agencies are summarized.
KW  - bioburdens
KW  - sterility tests
KW  - sterilization efficacy
KW  - sterilization methods
KW  - validation methods
Y1  - 2021
U6  - http://dx.doi.org/10.1002/pssa.202000732
SN  - 1862-6319
N1  - Corresponding author: Michael J. Schöning
VL  - 218
IS  - 13
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Molinnus, Denise
A1  - Drinic, Aleksander
A1  - Iken, Heiko
A1  - Kröger, Nadja
A1  - Zinser, Max
A1  - Smeets, Ralf
A1  - Köpf, Marius
A1  - Kopp, Alexander
A1  - Schöning, Michael Josef
T1  - Towards a flexible electrochemical biosensor fabricated from biocompatible Bombyx mori silk
JF  - Biosensors and Bioelectronics
Y1  - 2021
U6  - http://dx.doi.org/10.1016/j.bios.2021.113204
SN  - 0956-5663
VL  - 183
IS  - Art. 113204
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Wert, Stefan
A1  - Iken, Heiko
A1  - Schöning, Michael Josef
A1  - Matysik, Frank-Michael
T1  - Development of a temperature‐pulse enhanced electrochemical glucose biosensor and characterization of its stability via scanning electrochemical microscopy
JF  - Electroanalysis
N2  - Glucose oxidase (GOx) is an enzyme frequently used in glucose biosensors. As increased temperatures can enhance the performance of electrochemical sensors, we investigated the impact of temperature pulses on GOx that was drop-coated on flattened Pt microwires. The wires were heated by an alternating current. The sensitivity towards glucose and the temperature stability of GOx was investigated by amperometry. An up to 22-fold increase of sensitivity was observed. Spatially resolved enzyme activity changes were investigated via scanning electrochemical microscopy. The application of short (<100 ms) heat pulses was associated with less thermal inactivation of the immobilized GOx than long-term heating.
Y1  - 2021
U6  - http://dx.doi.org/10.1002/elan.202100089
SN  - 1521-4109
IS  - Early View
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Yoshinobu, Tatsuo
A1  - Schöning, Michael Josef
T1  - Light-addressable potentiometric sensors (LAPS) for cell monitoring and biosensing
JF  - Current Opinion in Electrochemistry
Y1  - 2021
U6  - http://dx.doi.org/10.1016/j.coelec.2021.100727
SN  - 2451-9103
IS  - In Press, Journal Pre-proof
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Givanoudi, Stella
A1  - Cornelis, Peter
A1  - Rasschaert, Geertrui
A1  - Wackers, Gideon
A1  - Iken, Heiko
A1  - Rolka, David
A1  - Yongabi, Derick
A1  - Robbens, Johan
A1  - Schöning, Michael Josef
A1  - Heyndrickx, Marc
A1  - Wagner, Patrick
T1  - Selective Campylobacter detection and quantification in poultry: A sensor tool for detecting the cause of a common zoonosis at its source
JF  - Sensors and Actuators B: Chemical
Y1  - 2021
U6  - http://dx.doi.org/10.1016/j.snb.2021.129484
SN  - 0925-4005
IS  - In Press, Journal Pre-proof
SP  - Article 129484
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Jablonski, Melanie
A1  - Münstermann, Felix
A1  - Nork, Jasmina
A1  - Molinnus, Denise
A1  - Muschallik, Lukas
A1  - Bongaerts, Johannes
A1  - Wagner, Torsten
A1  - Keusgen, Michael
A1  - Siegert, Petra
A1  - Schöning, Michael Josef
T1  - Capacitive field‐effect biosensor applied for the detection of acetoin in alcoholic beverages and fermentation broths
JF  - physica status solidi (a) applications and materials science
N2  - An acetoin biosensor based on a capacitive electrolyte–insulator–semiconductor (EIS) structure modified with the enzyme acetoin reductase, also known as butane-2,3-diol dehydrogenase (Bacillus clausii DSM 8716ᵀ), is applied for acetoin detection in beer, red wine, and fermentation broth samples for the first time. The EIS sensor consists of an Al/p-Si/SiO₂/Ta₂O₅ layer structure with immobilized acetoin reductase on top of the Ta₂O₅ transducer layer by means of crosslinking via glutaraldehyde. The unmodified and enzyme-modified sensors are electrochemically characterized by means of leakage current, capacitance–voltage, and constant capacitance methods, respectively.
KW  - acetoin
KW  - acetoin reductase
KW  - alcoholic beverages
KW  - biosensors
KW  - capacitive field-effect sensors
Y1  - 2021
U6  - http://dx.doi.org/10.1002/pssa.202000765
SN  - 1862-6319
VL  - 218
IS  - 13
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Jablonski, Melanie
A1  - Poghossian, Arshak
A1  - Severin, Robin
A1  - Keusgen, Michael
A1  - Wege, Christian
A1  - Schöning, Michael Josef
T1  - Capacitive Field-Effect Biosensor Studying Adsorption of Tobacco Mosaic Virus Particles
JF  - Micromachines
N2  - Plant virus-like particles, and in particular, tobacco mosaic virus (TMV) particles, are increasingly being used in nano- and biotechnology as well as for biochemical sensing purposes as nanoscaffolds for the high-density immobilization of receptor molecules. The sensitive parameters of TMV-assisted biosensors depend, among others, on the density of adsorbed TMV particles on the sensor surface, which is affected by both the adsorption conditions and surface properties of the sensor. In this work, Ta₂O₅-gate field-effect capacitive sensors have been applied for the label-free electrical detection of TMV adsorption. The impact of the TMV concentration on both the sensor signal and the density of TMV particles adsorbed onto the Ta₂O₅-gate surface has been studied systematically by means of field-effect and scanning electron microscopy methods. In addition, the surface density of TMV particles loaded under different incubation times has been investigated. Finally, the field-effect sensor also demonstrates the label-free detection of penicillinase immobilization as model bioreceptor on TMV particles.
KW  - capacitive field-effect sensor
KW  - plant virus detection
KW  - tobacco mosaic virus (TMV)
KW  - TMV adsorption
KW  - Ta₂O₅ gate
Y1  - 2021
U6  - http://dx.doi.org/10.3390/mi12010057
VL  - 12
IS  - 1
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Oliveira, Danilo A.
A1  - Molinnus, Denise
A1  - Beging, Stefan
A1  - Siqueira Jr, José R.
A1  - Schöning, Michael Josef
T1  - Biosensor Based on Self-Assembled Films of Graphene Oxide and Polyaniline Using a Field-Effect Device Platform
JF  - physica status solidi (a) applications and materials science
N2  - A new functionalization method to modify capacitive electrolyte–insulator–semiconductor (EIS) structures with nanofilms is presented. Layers of polyallylamine hydrochloride (PAH) and graphene oxide (GO) with the compound polyaniline:poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PANI:PAAMPSA) are deposited onto a p-Si/SiO2 chip using the layer-by-layer technique (LbL). Two different enzymes (urease and penicillinase) are separately immobilized on top of a five-bilayer stack of the PAH:GO/PANI:PAAMPSA-modified EIS chip, forming a biosensor for detection of urea and penicillin, respectively. Electrochemical characterization is performed by constant capacitance (ConCap) measurements, and the film morphology is characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). An increase in the average sensitivity of the modified biosensors (EIS–nanofilm–enzyme) of around 15% is found in relation to sensors, only carrying the enzyme but without the nanofilm (EIS–enzyme). In this sense, the nanofilm acts as a stable bioreceptor onto the EIS chip improving the output signal in terms of sensitivity and stability.
KW  - capacitive electrolyte–insulator–semiconductor sensors
KW  - graphene oxide
KW  - layer-by-layer technique
KW  - nanomaterials
KW  - polyaniline
Y1  - 2021
U6  - http://dx.doi.org/10.1002/pssa.202000747
SN  - 1862-6319
N1  - Corresponding author: José R. Siqueira Jr & Michael J. Schöning
VL  - 218
IS  - 13
SP  - 1
EP  - 9
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Welden, Rene
A1  - Nagamine Komesu, Cindy A.
A1  - Wagner, Patrick H.
A1  - Schöning, Michael Josef
A1  - Wagner, Torsten
T1  - Photoelectrochemical enzymatic penicillin biosensor: A proof-of-concept experiment
JF  - Electrochemical Science Advances
N2  - Photoelectrochemical (PEC) biosensors are a rather novel type of biosensors thatutilizelighttoprovideinformationaboutthecompositionofananalyte,enablinglight-controlled multi-analyte measurements. For enzymatic PEC biosensors,amperometric detection principles are already known in the literature. In con-trast, there is only a little information on H+-ion sensitive PEC biosensors. Inthis work, we demonstrate the detection of H+ions emerged by H+-generatingenzymes, exemplarily demonstrated with penicillinase as a model enzyme on atitanium dioxide photoanode. First, we describe the pH sensitivity of the sensorand study possible photoelectrocatalytic reactions with penicillin. Second, weshow the enzymatic PEC detection of penicillin.
KW  - enzymatic biosensor
KW  - penicillin
KW  - penicillinase
KW  - photoelectrochemistry
KW  - titanium dioxide photoanode
Y1  - 2021
U6  - http://dx.doi.org/10.1002/elsa.202100131
SN  - 2698-5977
N1  - Corresponding auhtor: Michael J. Schöning
VL  - 2
IS  - 4
SP  - 1
EP  - 5
PB  - Wiley-VCH
CY  - Weinheim
ER  -