@article{ArreolaKeusgenSchoening2017,
  author    = {Arreola, Julio and Keusgen, Michael and Sch{\"o}ning, Michael Josef},
  title     = {Effect of O2 plasma on properties of electrolyte-insulator-semiconductor structures},
  series = {physica status solidi a : applications and materials sciences},
  volume    = {214},
  journal   = {physica status solidi a : applications and materials sciences},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1862-6319},
  doi       = {10.1002/pssa.201700025},
  pages     = {Artikel 1700025},
  year      = {2017},
  abstract  = {Prior to immobilization of biomolecules or cells onto biosensor surfaces, the surface must be physically or chemically activated for further functionalization. Organosilanes are a versatile option as they facilitate the immobilization through their terminal groups and also display self-assembly. Incorporating hydroxyl groups is one of the important methods for primary immobilization. This can be done, for example, with oxygen plasma treatment. However, this treatment can affect the performance of the biosensors and this effect is not quite well understood for surface functionalization. In this work, the effect of O2 plasma treatment on EIS sensors was investigated by means of electrochemical characterizations: capacitance-voltage (C-V) and constant capacitance (ConCap) measurements. After O2 plasma treatment, the potential of the EIS sensor dramatically shifts to a more negative value. This was successfully reset by using an annealing process.},
  language  = {en}
}
@article{ArreolaKeusgenSchoening2019,
  author    = {Arreola, Julio and Keusgen, Michael and Sch{\"o}ning, Michael Josef},
  title     = {Toward an immobilization method for spore-based biosensors in oxidative environment},
  series = {Electrochimica Acta},
  volume    = {302},
  journal   = {Electrochimica Acta},
  publisher = {Elsevier},
  address   = {Amsterdam},
  doi       = {10.1016/j.electacta.2019.01.148},
  pages     = {394 -- 401},
  year      = {2019},
  language  = {en}
}
@article{ArreolaKeusgenWagneretal.2019,
  author    = {Arreola, Julio and Keusgen, Michael and Wagner, Torsten and Sch{\"o}ning, Michael Josef},
  title     = {Combined calorimetric gas- and spore-based biosensor array for online monitoring and sterility assurance of gaseous hydrogen peroxide in aseptic filling machines},
  series = {Biosensors and Bioelectronics},
  volume    = {143},
  journal   = {Biosensors and Bioelectronics},
  number    = {111628},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0956-5663},
  doi       = {10.1016/j.bios.2019.111628},
  year      = {2019},
  language  = {en}
}
@article{ArreolaMaetzkowDuranetal.2016,
  author    = {Arreola, Julio and M{\"a}tzkow, Malte and Dur{\´a}n, Marlena Palomar and Greeff, Anton and Keusgen, Michael and Sch{\"o}ning, Michael Josef},
  title     = {Optimization of the immobilization of bacterial spores on glass substrates with organosilanes},
  series = {Physica status solidi (A) : Applications and materials science},
  volume    = {213},
  journal   = {Physica status solidi (A) : Applications and materials science},
  number    = {6},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1862-6319},
  doi       = {10.1002/pssa.201532914},
  pages     = {1463 -- 1470},
  year      = {2016},
  abstract  = {Spores can be immobilized on biosensors to function as sensitive recognition elements. However, the immobilization can affect the sensitivity and reproducibility of the sensor signal. In this work, three different immobilization strategies with organosilanes were optimized and characterized to immobilize Bacillus atrophaeus spores on glass substrates. Five different silanization parameters were investigated: nature of the solvent, concentration of the silane, silanization time, curing process, and silanization temperature. The resulting silane layers were resistant to a buffer solution (e.g., Ringer solution) with a polysorbate (e.g., Tween®80) and sonication.},
  language  = {en}
}
@article{ArreolaOberlaenderMaetzkowetal.2017,
  author    = {Arreola, Julio and Oberl{\"a}nder, Jan and M{\"a}tzkow, M. and Keusgen, Michael and Sch{\"o}ning, Michael Josef},
  title     = {Surface functionalization for spore-based biosensors with organosilanes},
  series = {Electrochimica Acta},
  volume    = {241},
  journal   = {Electrochimica Acta},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0013-4686},
  doi       = {10.1016/j.electacta.2017.04.157},
  pages     = {237 -- 243},
  year      = {2017},
  abstract  = {In the present work, surface functionalization of different sensor materials was studied. Organosilanes are well known to serve as coupling agent for biomolecules or cells on inorganic materials. 3-aminopropyltriethoxysilane (APTES) was used to attach microbiological spores time to an interdigitated sensor surface. The functionality and physical properties of APTES were studied on isolated sensor materials, namely silicon dioxide (SiO2) and platinum (Pt) as well as the combined material on sensor level. A predominant immobilization of spores could be demonstrated on SiO2 surfaces. Additionally, the impedance signal of APTES-functionalized biosensor chips has been investigated.},
  language  = {en}
}
@article{BronderJessingPoghossianetal.2018,
  author    = {Bronder, Thomas and Jessing, Max P. and Poghossian, Arshak and Keusgen, Michael and Sch{\"o}ning, Michael Josef},
  title     = {Detection of PCR-Amplified Tuberculosis DNA Fragments with Polyelectrolyte-Modified Field-Effect Sensors},
  series = {Analytical Chemistry},
  volume    = {90},
  journal   = {Analytical Chemistry},
  number    = {12},
  publisher = {ACS Publications},
  address   = {Washington, DC},
  issn      = {0003-2700},
  doi       = {10.1021/acs.analchem.8b01807},
  pages     = {7747 -- 7753},
  year      = {2018},
  abstract  = {Field-effect-based electrolyte-insulator-semiconductor (EIS) sensors were modified with a bilayer of positively charged weak polyelectrolyte (poly(allylamine hydrochloride) (PAH)) and probe single-stranded DNA (ssDNA) and are used for the detection of complementary single-stranded target DNA (cDNA) in different test solutions. The sensing mechanism is based on the detection of the intrinsic molecular charge of target cDNA molecules after the hybridization event between cDNA and immobilized probe ssDNA. The test solutions contain synthetic cDNA oligonucleotides (with a sequence of tuberculosis mycobacteria genome) or PCR-amplified DNA (which origins from a template DNA strand that has been extracted from Mycobacterium avium paratuberculosis-spiked human sputum samples), respectively. Sensor responses up to 41 mV have been measured for the test solutions with DNA, while only small signals of ∼5 mV were detected for solutions without DNA. The lower detection limit of the EIS sensors was ∼0.3 nM, and the sensitivity was ∼7.2 mV/decade. Fluorescence experiments using SybrGreen I fluorescence dye support the electrochemical results.},
  language  = {en}
}
@article{BronderPoghossianJessingetal.2019,
  author    = {Bronder, Thomas and Poghossian, Arshak and Jessing, Max P. and Keusgen, Michael and Sch{\"o}ning, Michael Josef},
  title     = {Surface regeneration and reusability of label-free DNA biosensors based on weak polyelectrolyte-modified capacitive field-effect structures},
  series = {Biosensors and Bioelectronics},
  volume    = {126},
  journal   = {Biosensors and Bioelectronics},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0956-5663},
  doi       = {10.1016/j.bios.2018.11.019},
  pages     = {510 -- 517},
  year      = {2019},
  language  = {en}
}
@article{BronderPoghossianKeusgenetal.2017,
  author    = {Bronder, Thomas and Poghossian, Arshak and Keusgen, Michael and Sch{\"o}ning, Michael Josef},
  title     = {Label-free detection of double-stranded DNA molecules with polyelectrolyte-modified capacitive field-effect sensors},
  series = {tm - Technisches Messen},
  volume    = {84},
  journal   = {tm - Technisches Messen},
  number    = {10},
  publisher = {De Gruyter},
  address   = {Oldenbourg},
  doi       = {10.1515/teme-2017-0015},
  pages     = {628 -- 634},
  year      = {2017},
  abstract  = {In this study, polyelectrolyte-modified field-effect-based electrolyte-insulator-semiconductor (EIS) devices have been used for the label-free electrical detection of double-stranded deoxyribonucleic acid (dsDNA)molecules. The sensor-chip functionalization with a positively charged polyelectrolyte layer provides the possibility of direct adsorptive binding of negatively charged target DNA oligonucleotides onto theSiO2-chip surface.EIS sensors can be utilized as a tool to detect surface-charge changes; the electrostatic adsorption of oligonucleotides onto the polyelectrolyte layer leads to a measureable surface-potential change. Signals of 39mV have been recorded after the incubation with the oligonucleotide solution. Besides the electrochemical experiments, the successful adsorption of dsDNA onto the polyelectrolyte layer has been verified via fluorescence microscopy. The presented results demonstrate that the signal recording of EISchips, which are modified with a polyelectrolyte layer, canbe used as a favorable approach for a fast, cheap and simple detection method for dsDNA.},
  language  = {en}
}
@article{BronderPoghossianSchejaetal.2015,
  author    = {Bronder, Thomas and Poghossian, Arshak and Scheja, Sabrina and Wu, Chunsheng and Keusgen, Michael and Mewes, Dieter and Sch{\"o}ning, Michael Josef},
  title     = {DNA Immobilization and Hybridization Detection by the Intrinsic Molecular Charge Using Capacitive Field-Effect Sensors Modified with a Charged Weak Polyelectrolyte Layer},
  series = {Applied Materials \& Interfaces},
  volume    = {36},
  journal   = {Applied Materials \& Interfaces},
  number    = {7},
  publisher = {American Chemical Society},
  address   = {Washington, DC},
  doi       = {10.1021/acsami.5b05146},
  pages     = {20068 -- 20075},
  year      = {2015},
  abstract  = {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.},
  language  = {en}
}
@article{JablonskiMuenstermannNorketal.2021,
  author    = {Jablonski, Melanie and M{\"u}nstermann, Felix and Nork, Jasmina and Molinnus, Denise and Muschallik, Lukas and Bongaerts, Johannes and Wagner, Torsten and Keusgen, Michael and Siegert, Petra and Sch{\"o}ning, Michael Josef},
  title     = {Capacitive field-effect biosensor applied for the detection of acetoin in alcoholic beverages and fermentation broths},
  series = {physica status solidi (a) applications and materials science},
  volume    = {218},
  journal   = {physica status solidi (a) applications and materials science},
  number    = {13},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1862-6319},
  doi       = {10.1002/pssa.202000765},
  pages     = {7 Seiten},
  year      = {2021},
  abstract  = {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.},
  language  = {en}
}