18 research outputs found
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Fuelling an immune response: an ultrastructural study of immune-stimulated lymph nodes
A growing body of evidence suggests that adipocytes, and the triacylglycerol fatty acids within them, play an important role in supporting the inflammatory immune response. Inflammatory cytokines produced by an activated lymph node cause the release of fatty acids from neighbouring adipocytes, and the fatty acids are taken up into lymph node lymphoid cells, where they can be used as precursors for eicosanoid and plasma membrane synthesis, or as a fuel source. The mechanism of transport of fatty acids from adipocytes across the lymph node capsule and into lymphoid cells remains to be elucidated. Here we present evidence from light and electron microscopy that small fat-filled cells are found within the lymph node, and that 24 hours after an immune challenge they are associated with dendritic cells. The small adipocytes express S100 protein and insulin receptor, characteristics of mature adipocytes. Our observations suggest a mechanism for delivering triacylglycerol fatty acids directly to their site of use in supplying components for an immune response
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Membrane Scaffolds Enhance the Responsiveness and Stability of DNA-Based Sensing Circuits.
Target-induced DNA strand displacement is an excellent candidate for developing analyte-responsive DNA circuitry to be used in clinical diagnostics and synthetic biology. While most available technologies rely on DNA circuitry free to diffuse in bulk, here we explore the use of liposomes as scaffolds for DNA-based sensing nanodevices. Our proof-of-concept sensing circuit responds to the presence of a model target analyte by releasing a DNA strand, which in turn activates a fluorescent reporter. Through a combination of experiments and coarse-grained Monte Carlo simulations, we demonstrate that the presence of the membrane scaffold accelerates the process of oligonucleotide release and suppresses undesired leakage reactions, making the sensor both more responsive and robust
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Ionic liquid facilitated melting of the metal-organic framework ZIF-8.
Hybrid glasses from melt-quenched metal-organic frameworks (MOFs) have been emerging as a new class of materials, which combine the functional properties of crystalline MOFs with the processability of glasses. However, only a handful of the crystalline MOFs are meltable. Porosity and metal-linker interaction strength have both been identified as crucial parameters in the trade-off between thermal decomposition of the organic linker and, more desirably, melting. For example, the inability of the prototypical zeolitic imidazolate framework (ZIF) ZIF-8 to melt, is ascribed to the instability of the organic linker upon dissociation from the metal center. Here, we demonstrate that the incorporation of an ionic liquid (IL) into the porous interior of ZIF-8 provides a means to reduce its melting temperature to below its thermal decomposition temperature. Our structural studies show that the prevention of decomposition, and successful melting, is due to the IL interactions stabilizing the rapidly dissociating ZIF-8 linkers upon heating. This understanding may act as a general guide for extending the range of meltable MOF materials and, hence, the chemical and structural variety of MOF-derived glasses
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Sodium Ion Conductivity in Superionic IL-Impregnated Metal-Organic Frameworks: Enhancing Stability Through Structural Disorder
Abstract: Metal-organic frameworks (MOFs) are intriguing host materials in composite electrolytes due to their ability for tailoring host-guest interactions by chemical tuning of the MOF backbone. Here, we introduce particularly high sodium ion conductivity into the zeolitic imidazolate framework ZIF-8 by impregnation with the sodium-salt-containing ionic liquid (IL) (Na0.1EMIM0.9)TFSI. We demonstrate an ionic conductivity exceeding 2 × 10−4 S · cm−1 at room temperature, with an activation energy as low as 0.26 eV, i.e., the highest reported performance for room temperature Na+-related ion conduction in MOF-based composite electrolytes to date. Partial amorphization of the ZIF-backbone by ball-milling results in significant enhancement of the composite stability towards exposure to ambient conditions, up to 20 days. While the introduction of network disorder decelerates IL exudation and interactions with ambient contaminants, the ion conductivity is only marginally affected, decreasing with decreasing crystallinity but still maintaining superionic behavior. This highlights the general importance of 3D networks of interconnected pores for efficient ion conduction in MOF/IL blends, whereas pore symmetry is a less stringent condition
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Polymorphism in M(H2PO2)3 (M = V, Al, Ga) compounds with the perovskite-related ReO3 structure.
Trivalent metal hypophosphites with the general formula M(H2PO2)3 (M = V, Al, Ga) adopt the ReO3 structure, with each compound displaying two structural polymorphs. High-pressure synchrotron X-ray studies reveal a pressure-driven phase transition in Ga(H2PO2)3 that can be understood on the basis of ab initio thermodynamics
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Metal-organic framework and inorganic glass composites
Abstract: Metal-organic framework (MOF) glasses have become a subject of interest as a distinct category of melt quenched glass, and have potential applications in areas such as ion transport and sensing. In this paper we show how MOF glasses can be combined with inorganic glasses in order to fabricate a new family of materials composed of both MOF and inorganic glass domains. We use an array of experimental techniques to propose the bonding between inorganic and MOF domains, and show that the composites produced are more mechanically pliant than the inorganic glass itself
Tuning the Morphological Appearance of Iron(III) Fumarate: Impact on Material Characteristics and Biocompatibility
Iron(III) fumarate materials are well suited for biomedical applications as they feature biocompatible building blocks, porosity, chemical functionalizability, and magnetic resonance imaging (MRI) activity. The synthesis of these materials however is difficult to control, and it has been challenging to produce monodisperse particle sizes and morphologies that are required in medical use. Here, we report the optimization of iron(III) fumarate nano- and microparticle synthesis by surfactant-free methods, including room temperature, solvothermal, microwave, and microfluidic conditions. Four variants of iron(III) fumarate with distinct morphologies were isolated and are characterized in detail. Structural characterization shows that all iron(III) fumarate variants exhibit the metal–organic framework (MOF) structure of MIL-88A. Nanoparticles with a diameter of 50 nm were produced, which contain crystalline areas not exceeding 5 nm. Solvent-dependent swelling of the crystalline particles was monitored using in situ X-ray diffraction. Cytotoxicity experiments showed that all iron(III) fumarate variants feature adequate biotolerability and no distinct interference with cellular metabolism at low concentrations. Magnetic resonance relaxivity studies using clinical MRI equipment, on the other hand, proved that the MRI contrast characteristics depend on particle size and morphology. All in all, this study demonstrates the possibility of tuning the morphological appearance of iron(III) fumarate particles and illustrates the importance of optimizing synthesis conditions for the development of new biomedical materials
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Structure and Ionic Conductivity Properties of Ionic Liquid@Metal—Organic Framework Composites
IL@MOF (IL: ionic liquid; MOF: metal-organic framework) materials have been proposed as a candidate for solid-state electrolytes, combining the inherent non-flammability, high ionic conductivity, and high thermal and chemical stability of the ionic liquid with the host-guest interactions of the MOF. Although
there is a large degree of chemical tunability of the MOF and IL components, the ionic conductivity of the
IL in the composite is greatly reduced compared to the bulk due to the nanoconfinement of the IL within
the nanopores of the MOF. In the literature, studies have been limited to modifications to the organic
linkers or metal ions of the MOF, however, the structuring of the pore architecture can be modified in
several ways, explored in this thesis. Firstly, the addition of disordered mesopores from sol-gel synthesis conditions resulted in a hierarchically porous MOF superstructure containing both micropores (innate to the MOF) and mesopores (formed by controlled drying of the sol-gel system) and affords greater IL filling capacities as measured by nitrogen gas sorption experiments. Electrochemical impedance spectroscopy was used to compare the ionic conductivities of hierarchically porous IL@MOF composite with a standard microcrystalline IL@MOF composite. The theme of superstructures was further explored by utilising artificial opal polystyrene templates to generate ordered (inverse opal) and disordered macroporous networks within the MOF particles. The limited mechanical stability of the inverse opal MOF structure meant that gentle IL infiltration conditions were required for successful composite formation. Finally, a study on how the interaction between the IL and MOF components affects the structural transitions in ‘breathing’ MOF materials using variable temperature X-ray diffraction was carried out. In particular, the presence of the ionic liquid was demonstrated to lead to a distinct crystal structure which undergoes a similar phase transformation, but at a lower temperature
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Research data supporting Comparison of the ionic conductivity properties of microporous and mesoporous MOFs infiltrated with a Na-ion containing IL mixture
This repository contains the raw data necessary to reproduce figures and results from the published manuscript. The zipped data represents all of the techniques reported in this publication, including: Electrochemical Impedance Spectroscopy, Elemental Analysis, Nitrogen Gas Sorption, Proton Nuclear Magnetic Resonance, Scanning Electron Microscopy, Thermogravimetric Analysis, Transmission Electron Microscopy and X-ray Diffraction.
The folder_directory.txt included contains a detailed explanation of the filetypes and the contents of each folder and subfolder
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Adipocytes: a role in immunological memory?
Many reports in the literature suggest the involvement of perinodal adipocytes in inflammatory immune responses taking place in immune-challenged lymph nodes. Triacylglycerols (TAG) from the diet accumulate in adipocytes, and pass to lymph node lymphoid cells where they are used to provision immune responses. These adipocytes are specialised: TAG in perinodal adipose tissue are relatively enriched in polyunsaturated fatty acids compared with adipocytes that are not in proximity to lymphoid tissue. Polyunsaturated fatty acids can be used as precursors of eicosanoids and other regulatory molecules, as well as for membrane biosynthesis and energy. Thus perinodal adipocytes are specialized to provision immune cell metabolism.
Dendritic cells are well known as antigen presenting cells. They are migratory and are found in lymph nodes, and in significant numbers among perinodal adipocytes. Their numbers are modulated by dietary fatty acids. Dendritic cells can induce primary immune responses and allow the establishment of immunological memory. They are known to interact with adipocytes in various situations such as Crohn’s disease, and it has been reported that developing dendritic cells accumulate lipid, which may derive from adipocytes. Thus dendritic cells are candidates for involvement in the transfer of TAG to lymphoid cells mounting an immune response.
Here we show by light and electron microscopy that small adipocyte-like cells are normal residents of the lymph node, and that following an immune challenge they are observed in association with dendritic cells deep within the stimulated node.
We also show in an in vitro co-culture system that both adipocytes and lymphoid cells exhibit altered metabolic activities when they are cultured together compared to when they are cultured alone. This is indirect evidence for a functional molecular interaction in vivo.
We propose that this co-localisation and putative interaction is the basis for provisioning a rapid immune response by dendritic cells. This phenomenon may therefore represent part of the mechanism for the development and/or deployment of immunological memory