Entwicklung einer tropfenbasierten mikrofluidischen Plattform für das High-Throughput-Screening multizellulärer Systeme

Im Bereich der tropfenbasierten Mikrofluidik werden medizinische, biologische oder auch chemische Experimente in diskrete Reaktionsräume überführt. Diese als Tropfen bezeichneten Reaktionsräume besitzen als seriell angeordnete Mikroreaktoren ein hohes Anwendungspotenzial, sei es zur Optimierung von Screening-Prozessen für die Medikamentenentwicklung oder zur Manipulation von Zellen und 3D Zellstrukturen. Für solche Anwendungen bieten die derzeit existierenden Konzepte jedoch nicht die erforderliche Zuverlässigkeit und Praktikabilität. Vor allem die Aufrechterhaltung reproduzierbarer und stabiler Prozessbedingungen sind ausschlaggebende Faktoren als Voraussetzung für einen Durchbruch dieser Technologie am Markt. Insbesondere bei Anwendungen mit multizellulären Systemen wie nativen Gewebefragmenten oder in vitro kultivierten Sphäroiden sind besondere Voraussetzungen zu erfüllen. Beispielsweise ist die Verwendung oberflächenaktiver Substanzen (Tenside), die bei der Mehrzahl tropfenbasierter mikrofluidischer Applikationen zur Stabilisierung der Tropfen eingesetzt werden, nachteilig für Untersuchungen dieser Proben. Der Verzicht auf Tenside ist ein wichtiger Schritt in Richtung einer grundlegenden Akzeptanz tropfenbasierter Verfahren. Die in dieser Arbeit präsentierten Ergebnisse zeigen eine Alternative auf, bei der für das Handling und die Kultivierung multizellulärer Systeme auf die Verwendung von Tensiden verzichtet werden kann. Das im Rahmen der Forschungsarbeiten entwickelte technische System beruht auf neuartigen, mikrofluidischen Komponenten, die die hohen Ansprüche für das Handling multizellulärer Systeme erfüllen. Neben der Beschreibung der Systementwicklung steht die Charakterisierung der Einflussfaktoren auf die Tropfengenerierung im Mittelpunkt der Arbeit. Relevante Einflussgrößen wie die Kanalanordnung und deren Oberflächenbeschaffenheit sowie der Einfluss der Volumenströme und unterschiedlicher Probenmedien auf die Tropfengenerierung wurden untersucht. Die Arbeit beschreibt weiterhin die Entwicklung eines biomimetischen Ansatzes zur Steigerung der Stabilität der Tropfengenerierung durch die Verringerung des Adhäsionspotenzials wässriger Proben mit den Kanaloberflächen der Mikrosysteme. Damit ist die im Rahmen dieser Arbeit entwickelte mikrofluidische Plattform insbesondere für Anwendungen im Bereich der Biowissenschaften prädestiniert.In droplet-based microfluidics, medical, biological or chemical experiments take place in discrete reaction spaces named “droplets”. The droplet-based microfluidics offers a considerable potential for applications like optimization of screening processes for the development of drugs or for the manipulation of cells and 3D cell structures, respectively. However, for such applications the currently available concepts do not provide the necessary reliability and practicability. In particular, the maintenance of reproducible and stable process conditions are decisive factors for a breakthrough of this technology on the market. Applying multicellular systems like native tissue or spheroids cultivated in vitro, special requirements have to be fulfilled. For example, the use of surface-active substances (surfactants), which are applied for stabilizing the droplets in the majority of droplet-based microfluidics applications, is disadvantageous for investigations of cells and 3D cell structures in droplets. The abandonment of surface-active substances is an important step towards a fundamental acceptance of droplet-based microfluidic processes. The results presented in this work show an alternative to avoid the use of surface-active substances for the handling and cultivation of cells and 3D cell structures in droplets. The technical system developed as part of the research work is based on novel microfluidic components and meets the high demands on reproducibility and stability for handling cells and 3D cell structures. The results of the research work include the development of the entire droplet-based system as well as the investigations on the droplet generation process. This includes the investigation of basic parameters like surface properties of the microfluidic channels, the arrangement of the channels, the fluid flow conditions, and the kind of sample medium. Partial aspects of the extensive experiments that were performed to analyze the influence of the above mentioned parameters were also investigated by numerical simulations. In addition, the work describes the development of a biomimetic approach to increase the stability of droplet generation and to reduce the adhesion of aqueous droplets to the microchannel surfaces of the polymer chips. This approach succeeded even with samples containing anticoagulated whole blood. Concluding, the newly developed and characterized droplet-based microfluidic system points out a high application potential for the life sciences and especially for the field of individual medicine

Global fire emissions buffered by the production of pyrogenic carbon

Landscape fires burn 3–5 million km2 of the Earth’s surface annually. They emit 2.2 Pg of carbon per year to the atmosphere, but also convert a significant fraction of the burned vegetation biomass into pyrogenic carbon. Pyrogenic carbon can be stored in terrestrial and marine pools for centuries to millennia and therefore its production can be considered a mechanism for long-term carbon sequestration. Pyrogenic carbon stocks and dynamics are not considered in global carbon cycle models, which leads to systematic errors in carbon accounting. Here we present a comprehensive dataset of pyrogenic carbon production factors from field and experimental fires and merge this with the Global Fire Emissions Database to quantify the global pyrogenic carbon production flux. We found that 256 (uncertainty range: 196–340) Tg of biomass carbon was converted annually into pyrogenic carbon between 1997 and 2016. Our central estimate equates to 12% of the annual carbon emitted globally by landscape fires, which indicates that their emissions are buffered by pyrogenic carbon production. We further estimate that cumulative pyrogenic carbon production is 60 Pg since 1750, or 33–40% of the global biomass carbon lost through land use change in this period. Our results demonstrate that pyrogenic carbon production by landscape fires could be a significant, but overlooked, sink for atmospheric CO2

Size fractionation as a tool for separating charcoal of different fuel source and recalcitrance in the wildfire ash layer

Charcoal is a heterogeneous material exhibiting a diverse range of properties. This variability represents a serious challenge in studies that use the properties of natural charcoal for reconstructing wildfires history in terrestrial ecosystems. In this study, we tested the hypothesis that particle size is a sufficiently robust indicator for separating forest wildfire combustion products into fractions with distinct properties. For this purpose, we examined two different forest environments affected by contrasting wildfires in terms of severity: an eucalypt forest in Australia, which experienced an extremely severe wildfire, and a Mediterranean pine forest in Italy, which burned to moderate severity. We fractionated the ash/charcoal layers collected on the ground into four size fractions (>2, 2–1, 1–0.5, <0.5 mm) and analysed them for mineral ash content, elemental composition, chemical structure (by IR spectroscopy), fuel source and charcoal reflectance (by reflected-light microscopy), and chemical/thermal recalcitrance (by chemical and thermal oxidation). At both sites, the finest fraction (<0.5 mm) had, by far, the greatest mass. The C concentration and C/N ratio decreased with decreasing size fraction, while pH and the mineral ash content followed the opposite trend. The coarser fractions showed higher contribution of amorphous carbon and stronger recalcitrance. We also observed that certain fuel types were preferentially represented by particular size fractions. We conclude that the differences between ash/charcoal size fractions were most likely primarily imposed by fuel source and secondarily by burning conditions. Size fractionation can therefore serve as a valuable tool to characterise the forest wildfire combustion products, as each fraction displays a narrower range of properties than the whole sample. We propose the mineral ash content of the fractions as criterion for selecting the appropriate number of fractions to analyse

Development of a microfluidic platform for the synthesis of MPI tracer materials

To avoid the disadvantages of classical batch-wise coprecipitation in the synthesis of iron oxide nanoparticles we developed a microfluidic synthesis platform with continuous flow mode which enables a faster and more efficient adjustment of relevant parameters like pH-value, temperature and educt concentration. Initial results of the electrostatically stabilized particles demonstrate the high potential for the use as tracer in magnetic particle imaging or contrast agent in magnetic resonance imaging outperforming the efficacy of the current gold-standard Resovist®. &nbsp; Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009007, DOI: 10.18416/IJMPI.2020.200900

Flexible Toolbox of High-Precision Microfluidic Modules for Versatile Droplet-Based Applications

Although the enormous potential of droplet-based microfluidics has been successfully demonstrated in the past two decades for medical, pharmaceutical, and academic applications, its inherent potential has not been fully exploited until now. Nevertheless, the cultivation of biological cells and 3D cell structures like spheroids and organoids, located in serially arranged droplets in micro-channels, has a range of benefits compared to established cultivation techniques based on, e.g., microplates and microchips. To exploit the enormous potential of the droplet-based cell cultivation technique, a number of basic functions have to be fulfilled. In this paper, we describe microfluidic modules to realize the following basic functions with high precision: (i) droplet generation, (ii) mixing of cell suspensions and cell culture media in the droplets, (iii) droplet content detection, and (iv) active fluid injection into serially arranged droplets. The robustness of the functionality of the Two-Fluid Probe is further investigated regarding its droplet generation using different flow rates. Advantages and disadvantages in comparison to chip-based solutions are discussed. New chip-based modules like the gradient, the piezo valve-based conditioning, the analysis, and the microscopy module are characterized in detail and their high-precision functionalities are demonstrated. These microfluidic modules are micro-machined, and as the surfaces of their micro-channels are plasma-treated, we are able to perform cell cultivation experiments using any kind of cell culture media, but without needing to use surfactants. This is even more considerable when droplets are used to investigate cell cultures like stem cells or cancer cells as cell suspensions, as 3D cell structures, or as tissue fragments over days or even weeks for versatile applications

Early histological, microbiological, radiological, and clinical response to cemented and screw-retained all-ceramic single crowns

To assess the early histological, microbiological, radiological, and clinical response to cemented and screw-retained all-ceramic single-tooth implant-supported reconstructions

Generation of Cardiomyocytes in Pipe-Based Microbioreactor Under Segmented Flow

Background/Aims: Embryonic stem (ES) cells have got a broad range differentiation potential. The differentiation is initiated via aggregation of non-differentiated ES cells into embryoid body (EB) capable of multi-lineage development. However experimental variables present in standard differentiation techniques lead to high EB heterogeneity, affecting development into the cells of desired lineage, and do not support the process automatization and scalability. Methods: Here we present a novel pipe based microbioreactor (PBM) setup based on segmented flow, designed for spatial maintenance of temperature, nutrition supply, gas supply and sterility. Results: We verified PBM feasibility for continuous process generating cardiac cells starting from single ES cell suspension followed by EB formation for up to 10 days. The ES cells used in the study were genetically modified for cardiac-specific EGFP expression allowing optical monitoring of cardiomyocytes while EBs remained within PBM for up to 10 days. Efficiency of cardiac cells formation within PBM was similar compared to a standard hanging drop based protocol. Conclusion: Our findings ensure further development of microfluidic bioreactor technology to enable robust cardiomyocytes production for needs of drug screening, tissue engineering and other applications. (C) 2016 The Author(s) Published by S. Karger AG, Base