@inproceedings{EllingerMeisterGrosaetal., author = {Ellinger, Frank and Meister, Tilo and Grosa, Patrick and Jamshidi, Kambiz and Ihle, David and Franchi, Norman and Wagner, Jens and Richter, Andreas and Fettweis, Gerhard and Fitzek, Frank and Kreissig, Martin and Klessig, Henrik and Kraemer, Rolf and Richter, Klaus and Frotzscher, Andreas and L{\"o}hr, Robert and Winkler, Wolfgang and Zoeke, Dominik and Carot, Alexander and Bluschke, Andreas}, title = {Project FAST - Fast Actuators Sensors \& Transceivers}, series = {Microwave Conference (LAMC), IEEE MTT-S Latin America, 12-14 Dec. 2016 Puerto Vallarta, Mexico}, booktitle = {Microwave Conference (LAMC), IEEE MTT-S Latin America, 12-14 Dec. 2016 Puerto Vallarta, Mexico}, publisher = {IEEE}, address = {Piscataway, NJ}, isbn = {978-1-5090-4287-6}, pages = {3}, language = {en} } @misc{EisenhauerFrankWeigeltetal., author = {Eisenhauer, Nico and Frank, Karin and Weigelt, Alexandra and Bartkowski, Bartosz and Beugnon, R{\´e}my and Liebal, Katja and Mahecha, Miguel and Quaas, Martin and Al-Halbouni, Djamil and Bastos, Ana and Bohn, Friedrich J. and Brito, Mariana Madruga de and Denzler, Joachim and Feilhauer, Hannes and Fischer, Rico and Fritsche, Immo and Guimaraes-Steinicke, Claudia and H{\"a}nsel, Martin and Haun, Daniel B. M. and Herrmann, Hartmut and Huth, Andreas and Kalesse-Los, Heike and Koetter, Michael and Kolleck, Nina and Krause, Melanie and Kretschmer, Marlene and Leit{\~a}o, Pedro J. and Masson, Torsten and Mora, Karin and M{\"u}ller, Birgit and Peng, Jian and P{\"o}hlker, Mira L. and Ratzke, Leonie and Reichstein, Markus and Richter, Solveig and R{\"u}ger, Nadja and S{\´a}nchez-Parra, Beatriz and Shadaydeh, Maha and Sippel, Sebastian and Tegen, Ina and Thr{\"a}n, Daniela and Umlauft, Josefine and Wendisch, Manfred and Wolf, Kevin and Wirth, Christian and Zacher, Hannes and Zaehle, S{\"o}nke and Quaas, Johannes}, title = {A belowground perspective on the nexus between biodiversity change, climate change, and human well-being}, series = {Journal of Sustainable Agriculture and Environment}, volume = {3}, journal = {Journal of Sustainable Agriculture and Environment}, number = {2}, publisher = {Wiley}, issn = {2767-035X}, doi = {10.1002/sae2.12108}, pages = {12}, abstract = {Soil is central to the complex interplay among biodiversity, climate, and society. This paper examines the interconnectedness of soil biodiversity, climate change, and societal impacts, emphasizing the urgent need for integrated solutions. Human-induced biodiversity loss and climate change intensify environmental degradation, threatening human well-being. Soils, rich in biodiversity and vital for ecosystem function regulation, are highly vulnerable to these pressures, affecting nutrient cycling, soil fertility, and resilience. Soil also crucially regulates climate, influencing energy, water cycles, and carbon storage. Yet, climate change poses significant challenges to soil health and carbon dynamics, amplifying global warming. Integrated approaches are essential, including sustainable land management, policy interventions, technological innovations, and societal engagement. Practices like agroforestry and organic farming improve soil health and mitigate climate impacts. Effective policies and governance are crucial for promoting sustainable practices and soil conservation. Recent technologies aid in monitoring soil biodiversity and implementing sustainable land management. Societal engagement, through education and collective action, is vital for environmental stewardship. By prioritizing interdisciplinary research and addressing key frontiers, scientists can advance understanding of the soil biodiversity-climate change-society nexus, informing strategies for environmental sustainability and social equity.}, language = {en} } @inproceedings{AmneusTunerMaussetal., author = {Amn{\´e}us, Per and Tun{\´e}r, Martin and Mauß, Fabian and Collin, Robert and Nygren, Jenny and Richter, Mattias and Ald{\´e}n, Marcus and Kraft, Markus and Bhave, Amit and Hildingsson, Leif and Johansson, Bengt}, title = {"Formaldehyd and Hydroxyl Radicals in an HCCI Engine - Calculations and Measurements"}, doi = {10.4271/2007-01-0049}, language = {en} } @techreport{HirschlReusswigWeissetal., author = {Hirschl, Bernd and Reusswig, Fritz and Weiß, Julika and B{\"o}lling, Lars and Bost, Mark and Flecken, Ursula and Haag, Leilah and Heiduk, Philipp and Klemm, Patrick and Lange, Christoph and Lass, Wiebke and Richter, Paul-Martin and Rupp, Johannes and Salecki, Steven and Schwarz, Uwe and Weyer, Gregor and Voigt, Rainer}, title = {Entwurf f{\"u}r ein Berliner Energie - und Klimaschutzprogramm (BEK), Endbericht, November 2015}, address = {Berlin}, pages = {418}, abstract = {Der Berliner Senat hat sich zum Ziel gesetzt bis 2050 klimaneutral zu werden. Das I{\"O}W war bereits an der Machbarkeitsstudie „Klimaneutrales Berlin 2050" beteiligt. Darauf aufbauend wurde nun das Berliner Energie- und Klimaschutzprogramm entwickelt. Unter der Gesamtprojektleitung des I{\"O}W wurden hierf{\"u}r gemeinsam mit sieben Partnerinstitutionen konkrete Strategien f{\"u}r die Handlungsfelder Energieversorgung, Geb{\"a}ude und Stadtentwicklung, Wirtschaft, private Haushalte und Konsum sowie Verkehr erarbeitet. Das Projekt zeichnet sich durch einen breit angelegten Beteiligungsprozess aus, in den sowohl ausgew{\"a}hlte Akteure der Fach{\"o}ffentlichkeit im Rahmen von Workshops, als auch die breite {\"O}ffentlichkeit, haupts{\"a}chlich in Form eines Online-Dialoges, miteingebunden werden. Der Entwurf wurde im Auftrag der Senatsverwaltung f{\"u}r Stadtentwicklung und Umwelt durch ein vom I{\"O}W gef{\"u}hrtes Projektteam im Rahmen einer etwa einj{\"a}hrigen Bearbeitungszeit unter Einbeziehung der Berliner Stadtgesellschaft erarbeitet. Er dient als Vorlage f{\"u}r ein vom Senat zu verabschiedendes Programm, welches nach Vorgabe und zur Erg{\"a}nzung des geplanten Berliner Energiewendegesetzes (EWG Bln) zu erstellen ist. Bei der hier vorliegenden Ver{\"o}ffentlichung handelt es sich um den Endbericht dieses BEK-Entwurfs, der s{\"a}mtliche Maßnahmenvorschl{\"a}ge und deren Bewertung beinhaltet.}, language = {de} } @techreport{HirschlReusswigWeissetal., author = {Hirschl, Bernd and Reusswig, Fritz and Weiß, Julika and B{\"o}lling, Lars and Bost, Mark and Flecken, Ursula and Haag, Leilah and Heiduk, Philipp and Klemm, Patrick and Lange, Christoph and Lass, Wiebke and Richter, Paul-Martin and Rupp, Johannes and Salecki, Steven and Schwarz, Uwe and Weyer, Gregor and Voigt, Rainer}, title = {Entwurf f{\"u}r ein Berliner Energie- und Klimaschutzprogramm (BEK) - Technischer Anhang B}, publisher = {Senatsverwaltung f{\"u}r Stadtentwicklung und Umwelt}, address = {Berlin}, url = {http://nbn-resolving.de/urn:nbn:de:101:1-201601205042}, pages = {236}, abstract = {Der Berliner Senat hat sich zum Ziel gesetzt bis 2050 klimaneutral zu werden. Das I{\"O}W war in diesem Zuge bereits an der Machbarkeitsstudie „Klimaneutrales Berlon 2050" beteiligt. Darauf aufbauend wurde nun das Berliner Energie- und Klimaschutzprogramm entwickelt. Unter der Gesamtprojektleitung des I{\"O}W wurden hierf{\"u}r gemeinsam mit sieben Partnerinstitutionen konkrete Strategien f{\"u}r die Handlungsfelder Energieversorgung, Geb{\"a}ude und Stadtentwicklung, Wirtschaft, private Haushalte und Konsum sowie Verkehr erarbeitet. Das Projekt zeichnet sich durch einen breit angelegten Beteiligungsprozess aus, in den sowohl ausgew{\"a}hlte Akteure der Fach{\"o}ffentlichkeit im Rahmen von Workshops, als auch die breite {\"O}ffentlichkeit, haupts{\"a}chlich in Form eines Online-Dialoges, miteingebunden werden. Der Entwurf wurde im Auftrag der Senatsverwaltung f{\"u}r Stadtentwicklung und Umwelt durch ein vom I{\"O}W gef{\"u}hrtes Projektteam im Rahmen einer etwa einj{\"a}hrigen Bearbeitungszeit unter Einbeziehung der Berliner Stadtgesellschaft erarbeitet. Er dient als Vorlage f{\"u}r ein vom Senat zu verabschiedendes Programm, welches nach Vorgabe und zur Erg{\"a}nzung des geplanten Berliner Energiewendegesetzes (EWG Bln) zu erstellen ist. Der technische Anhang bietet einen zus{\"a}tzlichen Einblick in die methodische Herangehensweise als Erg{\"a}nzung zum Hauptbericht und Anhang A.}, language = {de} } @incollection{SpechtBehrensRichter, author = {Specht, Dieter and Behrens, Stefan and Richter, Martin}, title = {Strategische Planung mit Roadmaps - M{\"o}glichkeiten f{\"u}r das Innovationsmanagement, die Personalbedarfs- und die Fabrikplanung}, series = {Technologie-Roadmapping}, booktitle = {Technologie-Roadmapping}, editor = {M{\"o}hrle, Martin G. and Isenmann, Ralf}, publisher = {Springer}, address = {Berlin [u.a.]}, isbn = {978-3-662-52708-5}, doi = {10.1007/978-3-662-52709-2_5}, pages = {65 -- 82}, language = {de} } @incollection{SpechtBehrensRichter, author = {Specht, Dieter and Behrens, Stefan and Richter, Martin}, title = {Integration der Technologieplanung in die strategische Gesch{\"a}ftsfeldplanung mit Hilfe von Roadmaps}, series = {Technologie-Roadmapping}, booktitle = {Technologie-Roadmapping}, editor = {M{\"o}hrle, Martin G. and Isenmann, Ralf}, publisher = {Springer}, address = {Berlin [u.a.]}, isbn = {978-3-662-52708-5}, doi = {10.1007/978-3-662-52709-2_10}, pages = {159 -- 168}, language = {de} } @inproceedings{LehmannVossMartinetal., author = {Lehmann, Mario and Voß, Fr{\"a}nzi and Martin, Frank and Richter, Heiko and Anderer, Ursula}, title = {Chondrogenic microtissues with a lower differentiation degree used as in vitro transplants show improved integration in the tissue repair process in an in vitro therapy culture system}, series = {Regenerative Medicine}, volume = {10}, booktitle = {Regenerative Medicine}, number = {7S}, issn = {1746-0751}, pages = {S. 53}, language = {en} } @inproceedings{RichterWinkler, author = {Richter, Martin and Winkler, Herwig}, title = {Flow Shop Scheduling Optimization in the Chipboard Industry: A Simulation-based Analysis using Priority Dispatching Rules}, series = {24th International Conference on Production Research (ICPR 2017)}, booktitle = {24th International Conference on Production Research (ICPR 2017)}, publisher = {DEStech Publications}, address = {Lancaster, Pennsylvania}, isbn = {978-1-60595-507-0}, doi = {10.12783/dtetr/icpr2017/17625}, pages = {296 -- 301}, abstract = {This paper gives insights on the usability of single priority and multi-criteria dispatching rules for production scheduling based on the results for a German chipboard manufacturing plant. A discrete-event simulation of the manufacturing process has been modeled to compare different priority rules with an expert-based sequence for a real set of jobs. The simulation results show that using one single or multi criteria priority dispatching rule on the total production system basically leads to a poor performance, whereas using different rules for each machine will enhance the overall performance. Higher performance can be achieved by the expert based scheduling and individual multi criteria dispatching rules. Hence, a dynamic modification of the production schedule by switching the dispatching rules according to the current performance is proposed, considering unforeseen disturbances.}, language = {en} } @misc{RichterWinklerKaucheretal., author = {Richter, Martin and Winkler, Herwig and Kaucher, Christian and Sarram, Amirhossein}, title = {Investigation and analysis of accumulators for the use of electrochemical storage in hybrid shunting locomotives}, series = {Procedia CIRP}, volume = {81}, journal = {Procedia CIRP}, issn = {2212-8271}, doi = {10.1016/j.procir.2019.03.243}, pages = {1010 -- 1015}, abstract = {This paper evaluates storage batteries with respect to usage in hybrid shunting locomotives. Topics are the status quo of existing technologies as well as future electrochemical storage technologies. A target system is used to evaluate the technologies. Furthermore, relevant battery characteristics for the usage in hybrid shunting locomotives have been identified. The necessary data have been retrieved from current literature (document analysis) and by a survey made with scientific and industrial experts. The results of the study show, that batteries of the lithium-ion-technology with a lithium-titanate anode and a lithium-iron-phosphate cathode are currently the most suitable batteries for the use in hybrid shunting locomotives. Promising future technologies are under investigation, but these technologies are several years away from their market entry.}, language = {en} } @misc{UlrichKohlerFachetal., author = {Ulrich, Hanna-Sophie and Kohler, Emma and Fach, Eva-Maria and Spallek, Jacob and Richter, Matthias and Mlinarić, Martin}, title = {Healthcare needs among unaccompanied minor refugees: a study protocol of a qualitative study explaining access and utilisation across place and gender}, series = {BMJ Open}, volume = {10}, journal = {BMJ Open}, number = {9}, issn = {2044-6055}, doi = {10.1136/bmjopen-2020-038882}, pages = {8}, abstract = {Introduction: Several studies have identified that unaccompanied minor refugees (UMRs) are allegedly 'vulnerable' and belong to a high-risk group in terms of psychological distress and post-traumatic stress disorder due to their preflight, periflight and postflight experiences. Psychosocial care (PSC) is of high importance for UMRs, but little is known about barriers to access and utilisation of PSC across place and gender. The aims of this gender-sensitive qualitative study will be to build on the existing body of literature and to provide qualitative evidence on the contexts and mechanisms of PSC for male and female UMRs in Germany by comparing two German regions. Methods and analysis: Following the study preparing realist review, a qualitative study will be undertaken in Berlin and Central German cities. Approximately 24 experts from the field of PSC and 12 lay UMRs will participate in face-to-face, semistructured interviews. Data will be transcribed and analysed based on the grounded theory research paradigm. Ethics and dissemination: Only participants who have been informed in both German and their native tongue and who have signed a declaration of consent will be included in the study. The study will comply rigorously with German data protection standards. Approval from the Ethical Review Committee at Martin Luther University Halle-Wittenberg, Germany has been obtained and granted. The results of the study will be presented at several conferences and will be published in high-quality, peer-reviewed international journals. The results will display a differentiated picture of the PSC of UMRs in Germany. Such knowledge is a precondition for a 'science of change' that translates explanations into practical recommendations on how to improve healthcare policies.}, language = {en} } @misc{LangeErnstTeubneretal., author = {Lange, Felix and Ernst, Owen C. and Teubner, Thomas and Richter, Carsten and Schmidbauer, Martin and Skibitzki, Oliver and Schroeder, Thomas and Schmidt, Peer and Boeck, Torsten}, title = {In-plane growth of germanium nanowires on nanostructured Si(001)/SiO2 substrates}, series = {Nano Futures}, volume = {4}, journal = {Nano Futures}, number = {3}, issn = {2399-1984}, doi = {10.1088/2399-1984/ab82a0}, pages = {1 -- 8}, abstract = {Germanium (Ge) nanowires (NWs) were grown in-plane on nano-structured Si(001)/SiO2 substrates by molecular beam epitaxy using gold (Au) as the solvent. The site-selective NW growth was enabled by a rectangular array of gold droplets on silicon (Si) tips with an Au nuclei density below 0.25 μm-2 on the surrounding silicon oxide (SiO2). The initial growth of Ge NWs starting from Si-Au droplets with SixGe1-x nucleation from ternary alloy is discussed from a thermodynamic point of view. The in-plane NW elongation occurred within ⟨110⟩ directions on the substrate and NWs were mainly bounded by two 55◦ inclined 111 facets and a less pronounced planar (001) top facet. Fully relaxed crystal lattices of Ge NWs were observed from two-dimensional reciprocal space maps of x-ray diffraction measurements.}, language = {en} } @misc{UlrichKohlerSpalleketal., author = {Ulrich, Hanna-Sophie and Kohler, Emma and Spallek, Jacob and Richter, Matthias and Clauß, Daniel and Mlinarić, Martin}, title = {Explaining psychosocial care among unaccompanied minor refugees: a realist review}, series = {European child \& adolescent psychiatry}, volume = {31(2022)}, journal = {European child \& adolescent psychiatry}, number = {12}, issn = {1435-165X}, doi = {10.1007/s00787-021-01762-1}, pages = {1857 -- 1870}, abstract = {Research on the psychosocial care (PSC) of unaccompanied minor refugees (UMRs) has mainly taken a socioepidemiological approach and has focused on the perspectives of experts in the field. In contrast, the knowledge concerning the differing context factors and the underlying mechanisms of current PSC which could inform policy recommendations is scant. The study aims at unravelling the contexts, mechanisms and outcomes of PSC for UMRs. For a realist review (RR), scientific evidence and gray literature were synthesised consistent with the RAMESES publication standards for realist synthesis. Based on an iterative keyword search in electronic databases (e.g., PubMed) and screening, 34 works from 2005 to 2019 were included in a realist synthesis. Theory-informed context-mechanism-outcome configurations (CMOs) were extracted, to explain underlying processes and mechanisms. Characterised by their interrelatedness, the dominant CMOs included the UMRs' intersections of transitions (e.g., adolescence and migration), their needs for culture-, and gender-sensitive PSC, and the undersupply of PSC. These contexts and outcomes are mediated by pre-, peri- and post-migratory stressors as well as care structures and are moreover influenced by overarching discourses and concepts. They comprise adverse and beneficial mechanisms in the PSC of UMRs. The existing literature grasps the PSC of UMRs by different disciplines and approaches but does not offer a comprehensive overview on micro-macro intersections and included discourses. The inclusion of lay perspectives and an intersectional approach could inform health service research. The reflection of UMR-related categorical constructs of resilience and vulnerability, discourses of othering, as well as restrictive health policies may guide policy recommendations.}, language = {en} } @misc{StrobelAlvaradoChavarinLeszczynskietal., author = {Strobel, Carsten and Alvarado Chavarin, Carlos and Leszczynski, Sebastian and Richter, Karola and Knaut, Martin and Reif, Johanna and V{\"o}lkel, Sandra and Albert, Matthias and Wenger, Christian and Bartha, Johann Wolfgang and Mikolajick, Thomas}, title = {Improved Graphene-base Heterojunction Transistor with Different Collector Semi-conductors for High-frequency Applications}, series = {Advanced Materials Letters}, volume = {13}, journal = {Advanced Materials Letters}, number = {1}, issn = {0976-3961}, doi = {10.5185/amlett.2022.011688}, abstract = {A new kind of transistor device with a graphene monolayer embedded between two n-type silicon layers is fabricated and characterized. The device is called graphene-base heterojunction transistor (GBHT). The base-voltage controls the current of the device flowing from the emitter via graphene to the collector. The transit time for electrons passing by the ultrathin graphene layer is extremely short which makes the device very promising for high frequency RF-electronics. The output current of the device is saturated and clearly modulated by the base voltage. Further, the silicon collector of the GBHT is replaced by germanium to improve the device performance. This enabled the collector current to be increased by almost three orders of magnitude. Also, the common-emitter current gain (Ic/Ib) increased from 10-3 to approximately 0.3 for the newly designed device. However, the ON-OFF ratio of the improved germanium based GBHT has so far been rather low. Further optimizations are necessary in order to fully exploit the potential of the graphene-base heterojunction transistor.}, language = {en} } @misc{StrobelAlvaradoChavarinRichteretal., author = {Strobel, Carsten and Alvarado Chavarin, Carlos and Richter, Karola and Knaut, Martin and Reif, Johanna and Völkel, Sandra and Jahn, Andreas and Albert, Matthias and Wenger, Christian and Kirchner, Robert and Bartha, Johann Wolfgang and Mikolajick, Thomas}, title = {Novel Graphene Adjustable-Barrier Transistor with Ultra-High Current Gain}, series = {ACS Applied Materials \& Interfaces}, volume = {14}, journal = {ACS Applied Materials \& Interfaces}, number = {34}, issn = {1944-8244}, doi = {10.1021/acsami.2c10634}, pages = {39249 -- 39254}, abstract = {A graphene-based three terminal barristor device was proposed to overcome the low on/off ratios and insufficient current saturation of conventional graphene field effect transistors. In this study, we fabricated and analyzed a novel graphene-based transistor, which resembles the structure of the barristor but uses a different operating condition. This new device, termed graphene adjustable-barriers transistor (GABT), utilizes a semiconductor-based gate rather than a metal-insulator gate structure to modulate the device currents. The key feature of the device is the two graphene-semiconductor Schottky barriers with different heights that are controlled simultaneously by the gate voltage. Due to the asymmetry of the barriers, the drain current exceeds the gate current by several orders of magnitude. Thus, the GABT can be considered an amplifier with an alterable current gain. In this work, a silicon-graphene-germanium GABT with an ultra-high current gain (ID/IG up to 8 × 106) was fabricated, and the device functionality was demonstrated. Additionally, a capacitance model is applied to predict the theoretical device performance resulting in an on-off ratio above 106, a swing of 87 mV/dec, and a drivecurrent of about 1 × 106 A/cm2.}, language = {en} } @misc{KarnapkeRichterWerner, author = {Karnapke, Reinhardt and Richter, Martin and Werner, Matthias}, title = {Virtualization in robot swarms: past, present, and future}, series = {2024 IEEE 21st Consumer Communications \& Networking Conference (CCNC)}, journal = {2024 IEEE 21st Consumer Communications \& Networking Conference (CCNC)}, publisher = {IEEE}, isbn = {979-8-3503-0457-2}, doi = {10.1109/CCNC51664.2024.10454838}, pages = {1 -- 6}, abstract = {Robot swarms have come a long way since the first mobile sensor/actuator networks. Since then, we have seen the rise of operating systems for robots and swarm operating systems that ease the use of robots, and especially of large swarms of them, a lot. Still, the description of a task is often not easy and best done by experts. In this paper we envision future swarm operating systems, where task descriptions take a form which can be realized by non-experts. We describe our idea of hugely increased virtualization in the swarm and how this can be used to realize the aforementioned vision.}, language = {en} } @misc{RichterKarnapkeWerner, author = {Richter, Martin and Karnapke, Reinhardt and Werner, Matthias}, title = {Utilizing sensor and actuator virtualization to achieve a systemic view of mobile heterogeneous cyber-physical systems}, series = {Proceedings of the 14th International Conference on Simulation and Modeling Methodologies, Technologies and Applications}, journal = {Proceedings of the 14th International Conference on Simulation and Modeling Methodologies, Technologies and Applications}, publisher = {SCITEPRESS - Science and Technology Publications}, isbn = {978-989-758-708-5}, doi = {10.5220/0012715800003758}, pages = {207 -- 214}, abstract = {When programming cyber-physical systems, application developers currently utilize physical sensors and actuators individually to achieve the desired observations and impacts within the physical world. This is an error-prone and complex task given the size, heterogeneity, and mobility of prevailing cyber-physical systems. We introduce an application model that allows the application developers to take a physical perspective. By means of this model, the programmers describe desired observations and influences with respect to the physical world without directly referencing physical devices. We present an additional model for a runtime environment that transparently utilizes the available physical devices to reach the application developers' targets. We show that an implementation of our models is functional via simulation.}, language = {en} } @misc{MartinNeubertLutteretal., author = {Martin, Frank and Neubert, Annemarie and Lutter, Anne-Helen and Scholka, Jenny and Hentschel, Erik and Richter, Heiko and Anderer, Ursula}, title = {MTS, WST-8, and ATP viability assays in 2D and 3D cultures: Comparison of methodologically different assays in primary human chondrocytes}, series = {Clinical Hemorheology and Microcirculation}, volume = {88}, journal = {Clinical Hemorheology and Microcirculation}, publisher = {IOS Press}, issn = {ISSN 1386-0291}, doi = {10.3233/CH-248101}, pages = {3 -- 19}, abstract = {BACKGROUND: Tissue engineering enables the production of three-dimensional microtissues which mimic naturally occurring conditions in special tissues. These 3D culture systems are particularly suitable for application in regenerative medicine or experimental pharmacology and toxicology. Therefore, it is important to analyse the cells in their 3D microenvironment with regard to viability and differentiation. Tetrazolium assays (WST-8 and MTS) are still the methods of choice for estimating the number of living, metabolically active cells, with WST-8 being cell-impermeable compared to MTS. In contrast to these methods, the ATP assay is an endpoint method based on the luciferase-induced reaction of ATP with luciferin after cell lysis. OBJECTIVE:We compared three methodologically different proliferation/toxicity assays (MTS, WST-8, ATP) in monolayer (2D) and 3D culture systems to improve the technically challenging determination of the number of viable cells. METHODS: Chondrocytes were isolated from human articular cartilage. Three different test systems (MTS, WST-8, ATP) were applied to monolayer cells (2D, varying cell numbers) and spheroids (3D, different sizes) in 96-well plates. The intracellular ATP concentration was determined by luciferase-induced reaction of ATP with luciferin using a luminometer. Formazan formation was measured spectrophotometrically after different incubation periods. Evaluation was performed by phase contrast microscopy (toxicity), correlation of cell count and ATP concentration or absorption signal (Gompertz function) and propidium iodide (PI) staining to proof the cell lysis of all cells in spheroids. RESULTS: In 2D culture, all three assays showed a good correlation between the number of seeded cells and the ATP concentration or absorption data, whereas the MTS-assay showed the lowest specificity. In 3D culture, the spheroid sizes were directly related to the number of cells seeded. The absorption data of the WST-8 and MTS assay correlated only for certain spheroid size ranges, whereas the MTS-assay showed again the lowest specificity. Only the measured intracellular ATP content showed a linear correlation with all spheroid sizes ranging from 100-1000 µm. The WST-8 assay revealed the second-best sensitivity which allows the measurement of spheroids larger than 240 µm. Phase contrast observation of monolayer cells showed toxic effects of MTS after 6 h incubation and no signs of toxicity of WST-8. Staining with propidium iodide showed complete lysis of all cells in a spheroid in the ATP assay. CONCLUSION: Among tetrazolium-based assays, WST-8 is preferable to MTS because of its non-toxicity and better sensitivity. When determining the number of viable cells in the 2D system, caution is advised when using the ATP assay because of its two-phase slope of the correlation graph concerning cell number and intracellular ATP. In 3D systems of human chondrocytes, the ATP-assay is superior to the other two test systems, as the correlation graph between cell number and intracellular ATP is biphasic. Since differentiation processes or other metabolic events can influence the results of proliferation and toxicity assays (determination of viable cells), this should be taken into account when using these test systems.}, language = {en} }