INMdok (Leibniz Institute for New Materials)
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High glucose enhances antigen-independent CTL killing via TRAIL
Get PDFCytotoxic T lymphocytes (CTLs) are involved in development of diabetes. However, the impact of excessive glucose on CTL-mediated antigen-independent killing remains elusive. Here, we report that TNF-related apoptosis inducing ligand (TRAIL) is substantially up- regulated in CTLs in environments with high glucose (HG) both in vitro and in vivo. The PI3K- Akt-NFκB axis and non-mitochondrial reactive oxygen species are essential in HG-induced TRAIL upregulation in CTLs. TRAILhigh CTLs induce apoptosis of pancreatic beta cell line 1.4E7. Metformin and Vitamin D synergistically reduce HG-enhanced expression of TRAIL in CTLs and coherently protect 1.4E7 cells from TRAIL-mediated apoptosis. Notably, in patients with diabetes, correlation between Vitamin D concentrations in plasma and glucose levels is linked to HG-enhanced TRAIL expression on CTLs. Microarray data reveal that OXCT2, an important enzyme in ketone body catabolism, is a promising target in response to vitamin D. Our work not only reveals a novel mechanism of CTL involvement in progression of diabetes, but also establishes CTLs as a target for combined metformin and vitamin D therapy to protect pancreatic beta cells of diabetic patients.Competing Interest StatementThe authors have declared no competing interest
o-Nitrobenzyl-based polymer materials with light-regulated multi-functions
Get PDFo-Nitrobenzyl (oNB)-based polymers have been used as photodegradable materials/surfaces, and responsive biomaterials. While previous studies have mainly focused on the photodegradation of the material by intercalating oNB derivatives in the polymer chains, this thesis pays attention to the utilization of oNB photolysis to tailor the properties of materials, including interface functions, network topology, and bulk properties. To this end, two kinds of oNB based molecules with multifunctional units were designed and synthesized: 2-bromo-N-(2-nitro-3, 4-dihydroxyphenethyl)-2-methylpropanamide (NO2-BDAM, nitrodapomine based initiator) and 2-((2-bromo-2-methylpropanoyl)oxy)ethyl 4-(4-(1-(acryloyloxy)ethyl)-2-methoxy-5-nitrophenoxy) butanoate (vinyl-oNB-Br, photolabile inimer). In part 1, NO2-BDAM, in combination with Mn2(CO)10 as a visible light-sensitive additive, was used to control the growth and detachment of polymer brushes independently. In part 2, vinyl-oNB-Br was introduced into a double network material for in situ regulating topology from connected double network (c-DN) to disconnected double network (d-DN) by light exposure. In the last part, vinyl-oNB-Br was used to graft and detach polymer brushes from a network, leading to the change of network topology and material toughness. These results contribute to the topic of functionalized oNB based polymer systems and tunable topological polymer networks, providing useful strategies both in chemistry and materials.o-Nitrobenzyl (oNB)-basierte Polymere wurden als photoabbaubare Materialien/Oberflächen und responsive Biomaterialien verwendet. Während sich frühere Studien hauptsächlich auf den Photoabbau des Materials durch die Interkalation von oNB-Derivaten in den Polymerketten konzentrierten, widmet sich diese Arbeit der Nutzung der oNB-Photolyse, um die Eigenschaften von Materialien, einschließlich Grenzflächenfunktionen, Netzwerktopologie und Volumeneigenschaften, anzupassen. Zu diesem Zweck wurden zwei Arten von oNB-basierten Molekülen mit multifunktionellen Einheiten entworfen und synthetisiert: 2-Brom-N-(2-nitro-3,4-dihydroxyphenethyl)-2-methylpropanamid (NO2-BDAM, Nitrodapomin-basierter Initiator) und 2 -((2-Brom-2-methylpropanoyl)oxy)ethyl 4-(4-(1-(Acryloyloxy)ethyl)-2-methoxy-5-nitrophenoxy)butanoat (vinyl-oNB-Br, photolabiles Inimer). In Teil 1 wurde NO2-BDAM in Kombination mit Mn2(CO)10 als Additiv für sichtbares Licht verwendet, um das Wachstum und die Ablösung von Polymerbürsten unabhängig voneinander zu kontrollieren. In Teil 2 wurde vinyl-oNB-Br in ein Doppelnetzwerkmaterial eingebracht, um die Topologie in situ vom verbundenen Doppelnetzwerk (c-DN) zum getrennten Doppelnetzwerk (d-DN) durch Lichteinwirkung zu regulieren. Im letzten Teil wurde Vinyl-oNB-Br zum Aufpfropfen und Ablösen von Polymerbürsten aus einem Netzwerk verwendet, was zu einer Änderung der Netzwerktopologie und Materialzähigkeit führte. Diese Ergebnisse tragen zum Thema funktionalisierte oNB-basierte Polymersysteme und abstimmbare topologische Polymernetzwerke bei und liefern nützliche Strategien sowohl in der Chemie als auch in den Materialien
Nanoporous Block Copolymer Membranes with Enhanced Solvent Resistance Via UV-Mediated Cross-Linking Strategies
Get PDFIn this work, a block copolymer (BCP) consisting of poly((butyl methacrylate-co-benzophenone methacrylate-co-methyl methacrylate)-block-(2-hydroxyethyl methacrylate)) (P(BMA-co-BPMA-co-MMA)-b-P(HEMA)) is prepared by a two-step atom-transfer radical polymerization (ATRP) procedure. BCP membranes are fabricated applying the self-assembly and nonsolvent induced phase separation (SNIPS) process from a ternary solvent mixture of tetrahydrofuran (THF), 1,4-dioxane, and dimethylformamide (DMF). The presence of a porous top layer of the integral asymmetric membrane featuring pores of about 30 nm is confirmed via scanning electron microscopy (SEM). UV-mediated cross-linking protocols for the nanoporous membrane are adjusted to maintain the open and isoporous top layer. The swelling capability of the noncross-linked and cross-linked BCP membranes is investigated in water, water/ethanol mixture (1:1), and pure ethanol using atomic force microscopy, proving a stabilizing effect of the UV cross-linking on the porous structures. Finally, the influence of the herein described cross-linking protocols on water-flux measurements for the obtained membranes is explored. As a result, an increased swelling resistance for all tested solvents is found, leading to an increased water flux compared to the pristine membrane. The herein established UV-mediated cross-linking protocol is expected to pave the way to a new generation of porous and stabilized membranes within the fields of separation technologies
T cell stiffness is enhanced upon formation of immunological synapse
Get PDFT cells are activated by target cells via an intimate contact, termed immunological synapse (IS). Cellular mechanical properties, especially stiffness, are essential to regulate cell functions. However, T cell stiffness at a subcellular level at the IS still remains largely elusive. In this work, we established an atomic force microscopy (AFM)-based elasticity mapping method on whole T cells to obtain an overview of the stiffness with a resolution of ~60 nm. Using primary human CD4+ T cells, we show that when T cells form IS with stimulating antibody-coated surfaces, the lamellipodia are stiffer than the cell body. Upon IS formation, T cell stiffness is enhanced both at the lamellipodia and on the cell body. Chelation of intracellular Ca2+ abolishes IS-induced stiffening at the lamellipodia but has no influence on cell-body-stiffening, suggesting different regulatory mechanisms of IS-induced stiffening at the lamellipodia and the cell body
Monitoring the thermally induced transition from sp3-hybridized into sp2-hybridized carbons
Get PDFThe preparation of carbons for technical applications is typically based on a treatment of a precursor, which is transformed into the carbon phase with the desired structural properties. During such treatment the material passes through several different structural stages, for example, starting from precursor molecules via an amorphous phase into crystalline-like phases. While the structure of non-graphitic and graphitic carbon has been well studied, the transformation stages from molecular to amorphous and non-graphitic carbon are still not fully understood. Disordered carbon often contains a mixture of sp3-, sp2-and sp1-hybridized bonds, whose analysis is difficult to interpret. We systematically address this issue by studying the transformation of purely sp3-hybridized carbons, that is, nanodiamond and adamantane, into sp2-hybridized non-graphitic and graphitic carbon. The precursor materials are thermally treated at different temperatures and the transformation stages are monitored. We employ Raman spectroscopy, WAXS and TEM to characterize the structural changes. We correlate the intensities and positions of the Raman bands with the lateral crystallite size La estimated by WAXS analysis. The behavior of the D and G Raman bands characteristic for sp2-type material formed by transforming the sp3-hybridized precursors into non-graphitic and graphitic carbon agrees well with that observed using sp2-structured precursors
Characterization of immune cell migration using microfabrication
Get PDFThe immune system provides our defense against pathogens and aberrant cells, including tumorigenic and infected cells. Motility is one of the fundamental characteristics that enable immune cells to find invading pathogens, control tissue damage, and eliminate primary developing tumors, even in the absence of external treatments. These processes are termed “immune surveillance.” Migration disorders of immune cells are related to autoimmune diseases, chronic inflammation, and tumor evasion. It is therefore essential to characterize immune cell motility in different physiologically and pathologically relevant scenarios to understand the regulatory mechanisms of functionality of immune responses. This review is focused on immune cell migration, to define the underlying mechanisms and the corresponding investigative approaches. We highlight the challenges that immune cells encounter in vivo, and the microfabrication methods to mimic particular aspects of their microenvironment. We discuss the advantages and disadvantages of the proposed tools, and provide information on how to access them. Furthermore, we summarize the directional cues that regulate individual immune cell migration, and discuss the behavior of immune cells in a complex environment composed of multiple directional cues
Reversible magnetism switching of iron oxide nanoparticle dispersions by controlled agglomeration
Get PDFThe controlled agglomeration of superparamagnetic iron oxide nanoparticles (SPIONs) was used to rapidly switch their magnetic properties. Small-angle X-ray scattering (SAXS) and dynamic light scattering showed that tailored iron oxide nanoparticles with phase-changing organic ligands shells agglomerate at temperatures between 5 °C and 20 °C. We observed the concurrent change in magnetic properties using magnetic particle spectroscopy (MPS) with a temporal resolution at the order of seconds and found reversible switching of magnetic properties of SPIONs by changing their agglomeration state. The non-linear correlation between magnetization amplitude from MPS and agglomeration degree from SAXS data indicated that the agglomerates’ size distribution affected magnetic properties
Breakdown of continuum models for spherical probe adhesion tests on micropatterned surfaces
Get PDFThe adhesion of fibrillar dry adhesives, mimicking nature's principles of contact splitting, is commonly characterized by using axisymmetric probes having either a flat punch or spherical geometry. When using spherical probes, the adhesive pull-off force measured depends strongly on the compressive preload applied when making contact and on the geometry of the probe. Together, these effects complicate comparisons of the adhesive performance of micropatterned surfaces measured in different experiments. In this work we explore these issues, extending previous theoretical treatments of this problem by considering a fully compliant backing layer with an array of discrete elastic fibrils on its surface. We compare the results of the semi-analytical model presented to existing continuum theories, particularly with respect to determining a measurement system- and procedure-independent metric for the local adhesive strength of the fibrils from the global pull-off force. It is found that the discrete nature of the interface plays a dominant role across a broad range of relevant system parameters. Accordingly, a convenient tool for simulation of a discrete array is provided. An experimental procedure is recommended for use in conjunction with this tool in order to extract a value for the local adhesive strength of the fibrils, which is independent of the other system properties (probe radius, backing layer thickness, and preload) and thus is suitable for comparison across experimental studies
Bio-inspired photonic surfaces by enhanced Two-Photon Lithography
Get PDF2D and 3D photonic crystals active in the visible wave range are highly interesting for applications, such as waveguiding elements, sensors, or counterfeiting features. However, the tuneable production of such crystals with the current processes is challenging. Two-photon lithography (TPL), which is mainly used to manufacture microstructures, offers this versatility but currently suffers from insufficient structure resolution and mechanical stability for sub-micrometre structures. In the course of this work several novel approaches including an improved development and standing wave enhanced two-photon lithography are presented. These approaches improve the structure resolution and quality, and thus, allow stable features sizes down to 120 nm in horizontal and 45 nm in vertical direction. The new capabilities were used to fabricate distinct photonic crystals inspired by the 2D-pillar grating found on the moth eye and the 3D ‘Christmas tree’-like structures covering the wings of the Morpho-butterflies. Resulting structures were analysed in detail regarding their sizes and optical properties, showing highly effective diffraction, promising anti-reflection properties, and outstanding angle independent iridescence. The experimental work is supported by correlated simulations investigating the optical properties, structures sizes, and the influences of different experimental parameter settings relevant for the fabrication.2D und 3D photonische Kristalle, die mit sichtbarem Licht interagieren, finden zunehmend Verwendung in Wellenleitelementen, bei Sensoren oder Sicherheitsmerkmalen. Jedoch ist die Herstellung solcher Kristalle mit den derzeitigen Methoden herausfordernd und komplex. Eine vielversprechende Technik wäre die Zweiphotonenlithografie, die gegenwärtig für die flexible Herstellung von Mikrostrukturen eingesetzt wird. Für die Fertigung von photonischen Kristallen, die hochqualitative Strukturen im Nanometerbereich voraussetzen, besitzt diese Technik jedoch keine ausreichende Strukturauflösung. In dieser Arbeit werden neue Verfahren wie ein verbesserter Entwicklungsprozess oder die Zweiphotonenlithograpie mit integrierter stehender Welle präsentiert. Diese Methoden erlauben die Herstellung von Submikrometerstrukturen mit einem Limit von 120 nm in horizontaler und 45°nm in vertikaler Richtung. Diese verbesserte Auflösung wurde genutzt, um zwei natürliche photonische Kristalle, die 2D optischen Gitter der Mottenaugen und die geschichteten 3D Strukturen der Morpho-Schmetterlinge, künstlich nachzuahmen. Die Untersuchung der optischen Eigenschaften dieser Strukturen zeigten hocheffektive Beugungs- und vielversprechende Antireflexeigenschaften sowie eine herausragende, winkelunabhängige Strukturfarbe. Die experimentelle Arbeit wurde durch Simulationen wie die der optischen Eigenschaften, der erwarteten Strukturgrößen und der Einflüsse von Prozessparametern auf die Herstellung unterstützt
Structural and chemical characterization of MoO 2 /MoS 2 triple-hybrid materials using electron microscopy in up to three dimensions
Get PDFThis work presents the synthesis of MoO2/MoS2 core/shell nanoparticles within a carbon nanotube network and their detailed electron microscopy investigation in up to three dimensions. The triple-hybrid core/shell material was prepared by atomic layer deposition of molybdenum oxide onto carbon nanotube networks, followed by annealing in a sulfur-containing gas atmosphere. High-resolution transmission electron microscopy together with electron diffraction, supported by chemical analysis via energy dispersive X-ray and electron energy loss spectroscopy, gave proof of a MoO2 core covered by few layers of a MoS2 shell within an entangled network of carbon nanotubes. To gain further insights into this complex material, the analysis was completed with 3D electron tomography. By using Z-contrast imaging, distinct reconstruction of core and shell material was possible, enabling the analysis of the 3D structure of the material. These investigations showed imperfections in the nanoparticles which can impact material performance, i.e. for faradaic charge storage or electrocatalysis