Specific ion effects ranking in the Hofmeister sequence are ubiquitous in biochemical, industrial, and atmospheric processes. In this experimental study specific ion effects inexplicable by the ...classical DLVO theory have been investigated at curved water–metal interfaces of gold nanoparticles synthesized by a laser ablation process in liquid in the absence of any organic stabilizers. Notably, ion-specific differences in colloidal stability occurred in the Hückel regime at extraordinarily low salinities below 50 μM, and indications of a direct influence of ion-specific effects on the nanoparticle formation process are found. UV–vis, zeta potential, and XPS measurements help to elucidate coagulation properties, electrokinetic potential, and the oxidation state of pristine gold nanoparticles. The results clearly demonstrate that stabilization of ligand-free gold nanoparticles scales proportionally with polarizability and antiproportionally with hydration of anions located at defined positions in a direct Hofmeister sequence of anions. These specific ion effects might be due to the adsorption of chaotropic anions (Br–, SCN–, or I–) at the gold/water interface, leading to repulsive interactions between the partially oxidized gold particles during the nanoparticle formation process. On the other hand, kosmotropic anions (F– or SO4 2–) seem to destabilize the gold colloid, whereas Cl– and NO3 – give rise to an intermediate stability. Quantification of surface charge density indicated that particle stabilization is dominated by ion adsorption and not by surface oxidation. Fundamental insights into specific ion effects on ligand-free aqueous gold nanoparticles beyond purely electrostatic interactions are of paramount importance in biomedical or catalytic applications, since colloidal stability appears to depend greatly on the type of salt rather than on the amount.
Harmful algal blooms (HABs) pose a major environmental concern across the globe. In abundance, cyanobacteria, or so-called green-blue algae can produce extremely dangerous cyanotoxins that harm ...humans and animals. This study focused on the mapping and distribution of intracellular macro-and micronutrients of the wide-spread freshwater cyanobacteria Microcystis aeruginosa (M. aeruginosa). Towards a better understanding of trace metal uptake and homeostasis throughout the cell cycle, we quantitatively mapped the spatial distribution of the elements P, K, Fe, Ca, Zn, Mn, and Cu across the ultrastructure of frozen-hydrated single cells using state-of-the-art X-ray nanofluorescence imaging at the Advanced Photon Source (APS) at Argonne National Laboratory. Bulk cellular nutrient and trace metal content correlated well with the total intracellular elemental content in individual cells obtained by quantitative synchrotron X-ray fluorescence measurements. Multi-dimensional mappings showed P and K atoms colocalized as discrete semicircular hotspots that were analyzed with respect to their stoichiometry. Elevated Cu and Ca concentrations were detected along division plane of cells. P and K were found to have similar spatial elemental distribution with about 65% and 69% of the total cellular P and K, respectively, located at the hotspots. The P and K colocalization were refined further using nanotomography, showing a K envelope surrounding the P core. Inorganic P and organic P compounds were specified using solution-state 31P nuclear magnetic resonance (NMR) spectroscopy from M. aeruginosa. Of the total extracted P determined by 31P NMR spectroscopy, 47% were found to be nucleotides while only 11% were polyphosphates. Multimodal X-ray imaging provides a better understanding of intracellular biochemical processes in cyanobacteria, helping us monitor and combat an emerging environmental threat.
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•Quantitative 2-3D elemental mappings obtained using synchrotron X-ray fluorescence.•Nanotomography distribution of P, K, Fe, and Ca.•P and K atoms colocalized as discrete semicircular hotspots.•Ca and Cu atoms present at division interface and on surface of the cells.•P compounds identified within Microcystis using solution-state 31P NMR spectroscopy.
Exosomes have gained recognition in cancer diagnostics and therapeutics. However, most exosome isolation methods are time-consuming, costly, and require bulky equipment, rendering them unsuitable for ...point-of-care (POC) settings. Microfluidics can be the key to solving these challenges. Here, we present a double filtration microfluidic device that can rapidly isolate exosomes via size-exclusion principles in POC settings. The device can efficiently isolate exosomes from 50-100 µL of plasma within 50 min. The device was compared against an already established exosome isolation method, polyethylene glycol (PEG)-based precipitation. The findings showed that both methods yield comparable exosome sizes and purity; however, exosomes isolated from the device exhibited an earlier miRNA detection compared to exosomes obtained from the PEG-based isolation. A comparative analysis of exosomes collected from membrane filters with 15 nm and 30 nm pore sizes showed a similarity in exosome size and miRNA detection, with significantly increased sample purity. Finally, TEM images were taken to analyze how the developed devices and PEG-based isolation alter exosome morphology and to analyze exosome sizes. This developed microfluidic device is cost-efficient and time-efficient. Thus, it is ideal for use in low-resourced and POC settings to aid in cancer and disease diagnostics and therapeutics.
The accumulation and amyloid formation of amyloid-β (Aβ) peptides is closely associated with the pathology of Alzheimer's disease. The physiological environment wherein Aβ aggregation happens is ...crowded with a large variety of metal ions including Zn2+. In this study, we investigated the role of Zn2+ in regulating the aggregation kinetics of Aβ40 peptide. Our results show that Zn2+ can shift a typical single sigmoidal aggregation kinetics of Aβ40 to a biphasic aggregation process. Zn2+ aids in initiating the rapid self-assembly of monomers to form oligomeric intermediates, which further grow into amyloid fibrils in the first aggregation phase. The presence of Zn2+ also retards the appearance of the second aggregation phase in a concentration dependent manner. In addition, our results show that a natural dipeptide, carnosine, can greatly alleviate the effect of Zn2+ on Aβ aggregation kinetics, most likely by coordinating with the metal ion to form chelates. These results suggest a potential in vivo protective effect of carnosine against the cytotoxicity of Aβ by suppressing Zn2+-induced rapid formation of Aβ oligomers.
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•Zn2+ shifts a typical single sigmoidal aggregation kinetics of Aβ40 to a biphasic process.•Zn2+ facilitates the rapid formation oligomers in the first aggregation phase.•Zn2+ retards the second aggregation phase in a concentration dependent manner.•Carnosine greatly reduces the effect of Zn2+ on Aβ aggregation by coordinating with Zn2+.
Harmful levels of environmental contaminants, such as arsenic (As), persist readily in the environment, threatening safe drinking water supplies in many parts of the world. In this paper, we present ...a straightforward and cost-effective filtration technology for the removal of arsenate from potable water. Biocomposite filters comprised of nanocrystalline iron oxides or oxyhydroxides mineralized within lignocellulose scaffolds constitute a promising low cost, low-tech avenue for the removal of these contaminants. Two types of iron oxide mineral phases, 2-line ferrihydrite (Fh) and magnetite (Mt), were synthesized within highly porous balsa wood using an environmentally benign modification process and studied in view of their effective removal of As from contaminated water. The mineral deposition pattern, minerology, as well as crystallinity, were assessed using scanning electron microscopy, transmission electron microscopy, micro-computed X-ray tomography, confocal Raman microscopy, infrared spectroscopy, and X-ray powder diffraction. Our results indicate a preferential distribution of the Fh mineral phase within the micro-porous cell wall and radial parenchyma cells of rays, while Mt is formed primarily at the cell wall/lumen interface of vessels and fibers. Water samples of known As concentrations were subjected to composite filters in batch incubation and gravity-driven flow-through adsorption tests. Eluents were analyzed using microwave plasma optical emission spectroscopy (MP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). By subjecting the filters to a flow of contaminated water, the time for As uptake was reduced to minutes rather than hours, while immobilizing the same amount of As. The retention of As within the composite filter was further confirmed through energy-dispersive X-ray mappings. Apart from addressing dangerously high levels of arsenate in potable water, these versatile iron oxide lignocellulosic filters harbor tremendous potential for addressing current and emerging environmental contaminants that are known to adsorb on iron oxide mineral phases, such as phosphate, polycyclic aromatic hydrocarbons or heavy metals.
Harmful levels of environmental contaminants, such as arsenic (As), persist in the environment, threatening drinking water supplies in parts of the world. Nanocrystalline iron hydroxide wood filters can remove As from running and standing water.
Inspired by natural matrix-mediated biomineralisation, we present an artificial calcification approach for wood, which predominately targets the hardly accessible nanoporous cell wall structure ...rather than the micron-sized void system of the cell lumina. CaCO sub(3) can be deposited with this method deep inside the wood structure. Mineralisation of the wood cell wall architecture with CaCO sub(3) offers a green alternative to conventional fire-retardant systems.
Wood can be considered as a highly porous, three-dimensional organic scaffold. It can be mineralized to create hierarchically structured organic-inorganic hybrid materials with novel properties. In ...the present paper, the precipitation of CaCO
mineral in Norway spruce and European beech wood has been studied by alternating impregnation with aqueous and alcoholic electrolyte solutions. Microstructural imaging by SEM and confocal Raman microscopy shows the distribution of calcite and vaterite as two CaCO
polymorphs, which are deposited deep inside the cellular structure of the wood. The confined microenvironment of the wood cell wall seems to favor a formation of vaterite, as visible by XRD and Raman spectroscopy. In view of a practical application, the mineralization of wood opens up ways for sustainable wood-based hybrid materials with a significantly improved fire resistance, as proven
pyrolysis combustion flow calorimetry and cone calorimetry tests. Beyond that, this versatile solute-exchange approach provides an opportunity for the incorporation of a broad range of different mineral phases into wood for novel material property combinations.
A “grafting‐from” polymerization approach within and at the complex and heterogeneous macromolecular assembly of wood cell walls is shown. The approach allows for the implementation of novel ...functionalities in renewable and functional wood‐based materials. The native wood structure is retained and used as a hierarchical multiscale framework for a modular two‐step polymerization process. The versatility and potential of the approach is shown by a polymerization of either hydrophobic or hydrophilic and pH‐responsive monomers in the wood structure. Characterization of the modified wood reveals the presence of polymer in the cell wall, and the new properties of these wood materials are discussed.
Towards smart wood‐based materials: The natural wood structure is used as a support to graft vinyl and acrylate monomers. The hydroxyls groups from wood are functionalized with azo‐based initiators, which can further initiate polymerization in/from the cell wall structure. The versatile technique yields wood‐based materials with new functionalities, and opens the way to new utilizations for bulk wood.
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