Synchrotron X-ray Fluorescence Microscopy Research Articles

Microbial Mobilization and Reprecipitation of Transition Metals in Waste Rock from an Abandoned Pyrite Mine: Implications for Metal Recovery

Abstract The Pyrite Mines in Sulphide, Ontario are a collection of historic mine workings representing one of more than 6000 abandoned mines in Ontario. Historic mines are receiving renewed interest as potential sources of critical minerals for use in low carbon technologies. This study characterizes waste rock from the Pyrite Mines in the context of metal distribution, microbial activity, bioleaching, and acid mine drainage (AMD) bioremediation for the recovery of metals. Acidophilic Fe-oxidizing bacteria cultured from the waste rock produced schwertmannite [Fe8O8(OH)8−2x(SO4)x·nH2O] and ammoniojarosite [NH4Fe3(SO4)2(OH)6] with similar morphologies to those often observed in acidic sulfidic mine settings. Fe- and S-oxidizing bacteria found naturally in the waste rock were used in waste rock bioleaching column experiments that demonstrated AMD formation and metal mobilization. The columns produced acidic leachates (pH = 1.75) containing dissolved constituents, including sulfur (1577 mg/L), iron (547.7 mg/L), nickel (12.6 mg/L), manganese (7.3 mg/L), copper (2.3 mg/L), zinc (2.0 mg/L), chromium (1.5 mg/L), and titanium (0.7 mg/L). The proportion of metals successfully leached from the waste rock was variable, with leaching efficiencies calculated for nickel (31%), manganese (10.5%), iron (1.5%), chromium (1.4%), and titanium (0.02%). The leachates produced by the bioleaching columns were amended in subsequent bioremediation columns using sulfate reducing bacteria cultured from the mine site. Remediation efficiencies for elements of interest were calculated as cobalt (100%), chromium (100%), copper (100%), iron (90%), titanium (68%), nickel (52%), manganese (52%), and sulfur (43%). Mapping elemental distributions in thin sections from one of the bioleaching columns using synchrotron X-ray fluorescence microscopy revealed the heterogeneity of the waste rock. Iron was observed in both euhedral mineral grains, likely pyrite, and in secondary cements coating grains in the waste rock. Nickel, manganese, and chromium were primarily co-located with the iron. Titanium was primarily co-located with calcium in titanite (CaTiSiO5), making it challenging to target with bioleaching. This study demonstrates the heterogeneous nature of metal distribution in waste rock from this historic mine site. It indicates that successful metal recovery from legacy mine waste will require such materials to be treated as anthropogenic mineral deposits that require “exploration” and characterization much like naturally occurring ore deposits.

Habitat-specific allocations of elements in Atriplex lentiformis seeds hint at adaptation to metal toxicity.

Self-sustaining vegetation in metal-contaminated areas is essential for rebuilding the ecological resilience and community stability in degraded lands. Metal-tolerant plants originating from contaminated post-mining areas may hold the key to successful plant establishment and growth. Yet, little is known about the impact of metal toxicity on reproductive strategies, metal accumulation and allocation patterns at the seed stage. Our research focused on metal tolerant Atriplex lentiformis, examining the effects of toxic metal(loid) concentration in soils on variability in its reproductive strategies, including germination patterns, elemental uptake, and allocation within the seeds. We employed advanced imaging techniques like synchrotron X-ray Fluorescence Microscopy (XFM; 2D scans and 3D tomograms) combined with ICP-MS to reveal significant differences in metal(loid) concentration and distribution within the seed structures of A. lentiformis from contrasting habitats. Exclusive Zn hotspots of high concentrations were found in the seeds of the metallicolous accession, primarily in the sensitive tissues of shoot apical meristems and root zones of the seed embryos. The findings of this study offer novel insights into phenotypic variability, metal tolerance and accumulation in plants from extreme environments. This knowledge can be applied to enhance plant survival and performance in land restoration efforts.

Impact of Pyrite Textures Prevalence on Flotation Performance in Mount Isa Copper Orebodies

ABSTRACT Pyrite, the most abundant sulfide mineral in base-metal deposits, presents significant challenges in mineral processing due to its deleterious effects when not properly managed. Its undesirable association with valuable minerals leads to low-quality concentrates, hindering smelting processes. Pyrite’s distinct textures and variable elemental compositions affect its floatability, with complex textures challenging to depress. Moreover, since multiple textures can be present within an orebody, their relative proportion in the ore could affect the overall flotation performance. Therefore, understanding the types of pyrite present, their abundance, and how they affect the flotation behavior of the ore is critical for an efficient depression and possible reclamation of pyrite. At the Mount Isa copper deposit, framboidal or ‘carbonaceous’ pyrite has been an ongoing challenge to the copper concentration operation, reducing the flotation circuit’s efficiency. Previous work by Yenial-Arslan et al. showed that high pyrite recoveries could be strongly linked to the prevalence of fine-grained pyrite. However, samples belonging to the coarse pyrite domain exhibited low natural floatability. This study further investigates the effect of the prevalence of pyrite textures on the flotation performance of copper orebodies at the Mount Isa deposit. The prevalence of pyrite textures was quantified and statistically linked to the natural floatability of pyrite, proving that fine-grained and framboidal pyrite greatly influence pyrite’s overall recovery. Furthermore, various mineral characterization techniques, such as synchrotron X-ray fluorescence microscopy (XFM) analysis, were used to explore how the natural floatability of pyrite was affected.

Trace Element Distribution and Arsenic Speciation in Toenails as Affected by External Contamination and Evaluation of a Cleaning Protocol.

Trace element concentrations in toenail clippings have increasingly been used to measure trace element exposure in epidemeological research. Conventional methods such as inductively coupled plasma mass spectrometry (ICP-MS) and high-performance liquid chromatography ICP-MS (HPLC-ICP-MS) are commonly used to measure trace elements and their speciation in toenails. However, the impact of the removal of external contamination on trace element quantification has not been thoroughly studied. In this work, the microdistribution of trace elements (As, Ca, Co, Cu, Fe, K, Mn, Ni, Rb, S, Sr, Ti, and Zn) in dirty and washed toenails and the speciation of As in situ in toenails were investigated using synchrotron X-ray fluorescence microscopy (XFM) and laterally resolved X-ray absorption near edge spectroscopy (XANES). XFM showed different distribution patterns for each trace element, consistent with their binding properties and nail structure. External (terrestrial) contamination was identified and distinguished from the endogenous accumulation of trace elements in toenails─contaminated areas were characterized by the co-occurrence of Co, Fe, and Mn with elements such as Ti and Rb (i.e., indicators of terrestrial contamination). The XANES spectra showed the presence of one As species in washed toenails, corresponding to As bound to sulfhydryl groups. In dirty specimens, a mixed speciation was found in localized areas, containing AsIII-S species and AsV species. ArsenicV is thought to be associated with surface contamination and exogenous As. These findings provide new insights into the speciation of arsenic in toenails, the microdistribution of trace elements, and the effectiveness of a cleaning protocol in removing external contamination.

Tracking element-mineral associations with unsupervised learning and dimensionality reduction in chemical and optical image stacks of thin sections

In-situ chemical analysis on thin sections is a cornerstone of geochemical research. Despite massive advances in digital image analysis, the interpretation of such data within the optical petrological context of the thin section has largely remained an analogue task in geochemistry. In this contribution, we registered optical and micro-chemical images from large thin section areas. Chemical datasets from scanning electron microscopy energy dispersive spectrometry (SEM-EDX) and Synchrotron X-ray fluorescence microscopy (S-XFM) were exported from proprietary software. We then evaluated two dimensionality reduction techniques against false-colour images and phase maps to test whether previously unnoticed features became discoverable. Principal component analysis (PCA) and deep sparse autoencoder (DSA) neural networks were used to summarise the multi-channel SEM-EDX and S-XFM into one single red-green-blue (RGB) representation each.Applied to an oceanic gabbro, a cratonic peridotite, and a pelagic limestone, the PCA-based dimensionality reduction was found to produce crisp RGB maps of phases with less noise than false-colour three-element RGB maps. They were registered with optical images to form a simple multi-channel input for pixel-based classification into classes (i.e., semantic segmentation). This was fast and worked well for typical igneous and metamorphic rocks (1–3 h routine). In the chemically quite homogenous limestone, the combined optical and S-XFM PCA input was successfully classified into many phases that were unclassifiable on the conventional SEM-EDX phase map. From the segmented optical and S-XFM PCA map, we exported pixel locations of classified accessory phases back into the original proprietary S-XFM software. This allowed quantification of trace elements whose X-ray peaks were invisible in the original S-XFM quantification.The DSA-based approach yielded phase maps with greater noise, but the technique was very strong at detecting subtle features. In the gabbro sample, the DSA image identified cryptic relict cores in clinopyroxene more clearly than in the previously used Cr concentration map. A DSA training set can be obtained on a small ROI to generate a consistent large area DSA image from which more fragmental cores were observed. For a ROI on the gabbro thin section, the DSA representation map and the blended optical image were segmented and inspected with a loupe tool. This allowed us to generate interactive histograms and bin-scatter concentration plots of selected phases and to search for co-variations of element concentrations. This approach can be expanded to include data from any in situ geochemical acquisition tools and may help discover previously unseen features in complex elemental imagery.

Micro-scale structural and chemical characterisation of deformed rocks with simultaneous in-situ synchrotron X-ray fluorescence and backscatter diffraction mapping

In-situ measurements of structural and chemical information on deformed rocks are required to understand microphysical deformation mechanisms, the relative timing of tectono-metamorphic events, and the interplay between deformation, fluid flow, and mineral reactions. Scanning-electron microscopy is commonly used for this purpose, because it can provide compositional information (via energy- or wavelength-dispersive spectroscopy and backscattered electron imaging) and crystallographic orientation data (via electron backscatter diffraction) for large fractions of thin sections down to nanometre resolution. However, elemental and crystal-structural data are usually acquired independently, introducing the need for registration of maps with different information and increasing instrument time. In addition, measuring element concentrations to levels below 1000 ppm increases acquisition times significantly, rendering the mapping of centimetre-scale areas with micrometre-resolution or below time-costly. Here, we introduce an alternative method using coeval synchrotron X-ray fluorescence microscopy (XFM) and X-ray backscatter diffraction mapping (XBDM) for the rapid acquisition of structural and compositional information down to the ppb level on whole rock sections with a spatial resolution down to ∼1 μm per pixel. We illustrate the principles of XFM/XBDM mapping on a sample of granitic mylonite. As example for the scientific potential of the new method, it is shown that the Ti distribution in quartz and feldspar can be accurately correlated with physical structure. A discussion of the limitations and opportunities of XFM/XBDM mapping for studying deformed rocks concludes this article.

Size-Dependent Penetration of Nanoparticles in Tumor Spheroids: A Multidimensional and Quantitative Study of Transcellular and Paracellular Pathways.

Tumor penetration of nanoparticles is crucial in nanomedicine, but the mechanisms of tumor penetration are poorly understood. This work presents a multidimensional, quantitative approach to investigate the tissue penetration behavior of nanoparticles, with focuses on the particle size effect on penetration pathways, in an MDA-MB-231 tumor spheroid model using a combination of spectrometry, microscopy, and synchrotron beamline techniques. Quasi-spherical gold nanoparticles of different sizes are synthesized and incubated with 2D and 3D MDA-MB-231 cells and spheroids with or without an energy-dependent cell uptake inhibitor. The distribution and penetration pathways of nanoparticles in spheroids are visualized and quantified by inductively coupled plasma mass spectrometry, two-photon microscopy, and synchrotron X-ray fluorescence microscopy. The results reveal that 15nm nanoparticles penetrate spheroids mainly through an energy-independent transcellular pathway, while 60nm nanoparticles penetrate primarily through an energy-dependent transcellular pathway. Meanwhile, 22nm nanoparticles penetrate through both transcellular and paracellular pathways and they demonstrate the greatest penetration ability in comparison to other two sizes. The multidimensional analytical methodology developed through this work offers a generalizable approach to quantitatively study the tissue penetration of nanoparticles, and the results provide important insights into the designs of nanoparticles with high accumulation at a target site.

Cadmium alters whole animal ionome and promotes the re-distribution of iron in intestinal cells of Caenorhabditis elegans.

The chronic exposure of humans to the toxic metal cadmium (Cd), either occupational or from food and air, causes various diseases, including neurodegenerative conditions, dysfunction of vital organs, and cancer. While the toxicology of Cd and its effect on the homeostasis of biologically relevant elements is increasingly recognized, the spatial distribution of Cd and other elements in Cd toxicity-caused diseases is still poorly understood. Here, we use Caenorhabditis elegans as a non-mammalian multicellular model system to determine the distribution of Cd at the tissue and cellular resolution and its effect on the internal levels and the distribution of biologically relevant elements. Using inductively coupled plasma-mass spectrophotometry (ICP-MS), we show that exposure of worms to Cd not only led to its internal accumulation but also significantly altered the C. elegans ionome. Specifically, Cd treatment was associated with increased levels of toxic elements such as arsenic (As) and rubidium (Rb) and a decreased accumulation of essential elements such as zinc (Zn), copper (Cu), manganese (Mn), calcium (Ca), cobalt (Co) and, depending on the Cd-concentration used in the assay, iron (Fe). We regarded these changes as an ionomic signature of Cd toxicity in C. elegans. We also show that supplementing nematode growth medium with Zn but not Cu, rescues Cd toxicity and that mutant worms lacking Zn transporters CDF-1 or SUR-7, or both are more sensitive to Cd toxicity. Finally, using synchrotron X-Ray fluorescence Microscopy (XRF), we showed that Cd significantly alters the spatial distribution of mineral elements. The effect of Cd on the distribution of Fe was particularly striking: while Fe was evenly distributed in intestinal cells of worms grown without Cd, in the presence of Cd, Fe, and Cd co-localized in punctum-like structures in the intestinal cells. Together, this study advances our understanding of the effect of Cd on the accumulation and distribution of biologically relevant elements. Considering that C. elegans possesses the principal tissues and cell types as humans, our data may have important implications for future therapeutic developments aiming to alleviate Cd-related pathologies in humans.

Elemental Mapping in a Preclinical Animal Model Reveals White Matter Copper Elevation in the Acute Phase of Central Nervous System Trauma.

Understanding the chemical events following trauma to the central nervous system could assist in identifying causative mechanisms and potential interventions to protect neural tissue. Here, we apply a partial optic nerve transection model of injury in rats and use synchrotron X-ray fluorescence microscopy (XFM) to perform elemental mapping of metals (K, Ca, Fe, Cu, Zn) and other related elements (P, S, Cl) in white matter tracts. The partial optic nerve injury model and spatial precision of microscopy allow us to obtain previously unattained resolution in mapping elemental changes in response to a primary injury and subsequent secondary effects. We observed significant elevation of Cu levels at multiple time points following the injury, both at the primary injury site and in neural tissue near the injury site vulnerable to secondary damage, as well as significant changes in Cl, K, P, S, and Ca. Our results suggest widespread metal dyshomeostasis in response to central nervous system trauma and that altered Cu homeostasis may be a specific secondary event in response to white matter injury. The findings highlight metal homeostasis as a potential point of intervention in limiting damage following nervous system injury.

Vibrational spectroscopy methods for investigation of the animal models of glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most common and devastating primary brain tumor among adults. It is highly lethal disease, as only 25% of patients survive longer than 1 year and only 5% more than 5 years from the diagnosis. To search for the new, more effective methods of treatment, the understanding of mechanisms underlying the process of tumorigenesis is needed.The new light on this problem may be shed by the analysis of biochemical anomalies of tissues affected by tumor growth. Therefore, in the present work, we applied the Fourier transform infrared (FTIR) and Raman microspectroscopy to evaluate changes in the distribution and structure of biomolecules appearing in the rat brain as a result of glioblastoma development. In turn, synchrotron X-ray fluorescence microscopy was utilized to determine the elemental anomalies appearing in the nervous tissue. To achieve the assumed goals of the study animal models of GBM were used. The rats were subjected to the intracranial implantation of glioma cells with different degree of invasiveness. For spectroscopic investigation brain slices taken from the area of cancer cells administration were used.The obtained results revealed, among others, the decrease content of lipids and compounds containing carbonyl groups, compositional and structural changes of proteins as well as abnormalities in the distribution of low atomic number elements within the region of tumor.

Spatial distribution of elements during osteoarthritis disease progression using synchrotron X-ray fluorescence microscopy

The osteochondral interface is a thin layer that connects hyaline cartilage to subchondral bone. Subcellular elemental distribution can be visualised using synchrotron X-ray fluorescence microscopy (SR-XFM) (1 μm). This study aims to determine the relationship between elemental distribution and osteoarthritis (OA) progression based on disease severity. Using modified Mankin scores, we collected tibia plates from 9 knee OA patients who underwent knee replacement surgery and graded them as intact cartilage (non-OA) or degraded cartilage (OA). We used a tape-assisted system with a silicon nitride sandwich structure to collect fresh-frozen osteochondral sections, and changes in the osteochondral unit were defined using quantified SR-XFM elemental mapping at the Australian synchrotron's XFM beamline. Non-OA osteochondral samples were found to have significantly different zinc (Zn) and calcium (Ca) compositions than OA samples. The tidemark separating noncalcified and calcified cartilage was rich in zinc. Zn levels in OA samples were lower than in non-OA samples (P = 0.0072). In OA samples, the tidemark had less Ca than the calcified cartilage zone and subchondral bone plate (P < 0.0001). The Zn–strontium (Sr) colocalisation index was higher in OA samples than in non-OA samples. The lead, potassium, phosphate, sulphur, and chloride distributions were not significantly different (P > 0.05). In conclusion, SR-XFM analysis revealed spatial elemental distribution at the subcellular level during OA development.

Examining the inorganic elemental composition of lobster phyllosoma (Panulirus ornatus) with X-ray fluorescence microscopy.

The ornate spiny rock lobster, Panulirus ornatus, is an attractive candidate for aquaculture. The larval stages of spiny lobsters, known as phyllosoma, are complex with many developmental stages. Very little is known about the inorganic element composition of phyllosoma. In this study, a novel method using synchrotron X-ray fluorescence microscopy (XFM) was applied to investigate the distributions of metals potassium (K), calcium (Ca), copper (Cu), zinc (Zn), the metalloid arsenic (As), and nonmetal bromine (Br) within individual phyllosoma at stages 3, 4, and 8 of their development. For the first time, 1µm resolution synchrotron XFM images of whole phyllosoma as well as closer examinations of their eyes, mouths, setae, and tails were obtained. Elements accumulated in certain locations within phyllosoma, providing insight into their likely biological role for these organisms. This information may be useful for the application of dietary supplementation in the future to closed larval cycle lobster aquaculture operations.

Proof of principle study: synchrotron X-ray fluorescence microscopy for identification of previously radioactive microparticles and elemental mapping of FFPE tissues

Biobanks containing formalin-fixed, paraffin-embedded (FFPE) tissues from animals and human atomic-bomb survivors exposed to radioactive particulates remain a vital resource for understanding the molecular effects of radiation exposure. These samples are often decades old and prepared using harsh fixation processes which limit sample imaging options. Optical imaging of hematoxylin and eosin (H&E) stained tissues may be the only feasible processing option, however, H&E images provide no information about radioactive microparticles or radioactive history. Synchrotron X-ray fluorescence microscopy (XFM) is a robust, non-destructive, semi-quantitative technique for elemental mapping and identifying candidate chemical element biomarkers in FFPE tissues. Still, XFM has never been used to uncover distribution of formerly radioactive micro-particulates in FFPE canine specimens collected more than 30 years ago. In this work, we demonstrate the first use of low-, medium-, and high-resolution XFM to generate 2D elemental maps of ~ 35-year-old, canine FFPE lung and lymph node specimens stored in the Northwestern University Radiobiology Archive documenting distribution of formerly radioactive micro-particulates. Additionally, we use XFM to identify individual microparticles and detect daughter products of radioactive decay. The results of this proof-of-principle study support the use of XFM to map chemical element composition in historic FFPE specimens and conduct radioactive micro-particulate forensics.

Cooper Basin REM gas shales after CO2 storage or acid reactions: Metal mobilisation and methane accessible pore changes

Shale - water - CO2 reactions may occur during CO2 geological storage, enhanced gas recovery, enhanced oil recovery, or supercritical CO2 fracturing. Shale-acid reactions occur during fracturing or acid stimulation. The mobilisation of metals from these processes can be an environmental concern if production water leaks or is released at surface. In addition, reactions may cause changes at the pore scale and affect gas or fluid flow. Three gas shales from the Australian Cooper Basin REM sequence were characterised for metals in minerals by synchrotron X-ray fluorescence microscopy. Metals including Zn, As, Ni, Cr were hosted in sphalerite associated with organic matter, Pb was in pyrite cement, and Mn was hosted in siderite. The shales were separately reacted with brine and supercritical CO2, with CO2-SO2, with dilute HCl, or with N2 at 100 °C and 20 MPa in batch reactors. The solution pH decreased during mineral reactions releasing metals to solution with the general concentrations from reaction with HCl > CO2-SO2 > CO2 > N2 and brine. Of the total available Pb, As, Li, and Zn in the shales, from 0 to 17%, 0.3 to 23%, 3 to 13%, and 0.4 to 28% was released to solution respectively. Corrosion of siderite and ankerite was observed after the CO2 reactions, with precipitation of Fe-oxides. After CO2-SO2 reaction siderite and ankerite were dissolved with pyrite, barite, and Fe-rich precipitates. HCl reactions resulted in complete dissolution of carbonates, with dissolution pits and no mineral precipitation observed. The changes to the fractions of gas accessible mesopores were characterised by small angle neutron scattering (SANS). The Epsilon Formation had the greatest fraction of open accessible pores in the SANS range of 10 to 150 nm, followed by the Murteree and Roseneath shale samples. After CO2 or CO2-SO2 reactions a small decrease in pore accessibility was more pronounced in the Murteree and Roseneath shales, consistent with mineral precipitation. HCl reaction resulted in opening of pores at 150 nm and closing of the smallest measured pores at 10 nm. Metals were mobilised from siderite, ankerite and sulphide minerals mainly, and were dependent on the mineral and metal content but also on the injected gas stream or fluid composition. CO2 based fluids may result in cleaner flow back water, than HCl based fluids. Geochemical reactions during CO2 storage or acid treatment in reactive shales cause pore changes that can affect gas migration. Mineral precipitation during CO2 and CO2-SO2 reactions can result in favourable self-sealing.

The use of synchrotron X-ray fluorescent imaging to study distribution and content of elements in chemically fixed single cells: a case study using mouse pancreatic beta-cells.

Synchrotron X-ray fluorescence microscopy (SXRF) presents a valuable opportunity to study the metallome of single cells because it simultaneously provides high-resolution subcellular distribution and quantitative cellular content of multiple elements. Different sample preparation techniques have been used to preserve cells for observations with SXRF, with a goal to maintain fidelity of the cellular metallome. In this case study, mouse pancreatic beta-cells have been preserved with optimized chemical fixation. We show that cell-to-cell variability is normal in the metallome of beta-cells due to heterogeneity and should be considered when interpreting SXRF data. In addition, we determined the impact of several immunofluorescence (IF) protocols on metal distribution and quantification in chemically fixed beta-cells and found that the metallome of beta-cells was not well preserved for quantitative analysis. However, zinc and iron qualitative analysis could be performed after IF with certain limitations. To help minimize metal loss using samples that require IF, we describe a novel IF protocol that can be used with chemically fixed cells after the completion of SXRF.

Spatiotemporal Visualization and Chemical Identification of the Metal Diffusion Layer at the Electrochemical Interface

The diffusion layer created by transition metal (TM) dissolution is ubiquitous at the electrochemical solid-liquid interface and plays a key role in determining electrochemical performance. Tracking the spatiotemporal dynamics of the diffusion layer has remained an unresolved challenge. With spatially resolved synchrotron X-ray fluorescence microscopy and micro-X-ray absorption spectroscopy, we demonstrate the in situ visualization and chemical identification of the dynamic diffusion layer near the electrode surface under electrochemical operating conditions. Our method allows for direct mapping of the reactive electrochemical interface and provides insights into engineering the diffusion layer for improving electrochemical performance.

Synchrotron XFM tomography for elucidating metals and metalloids in hyperaccumulator plants.

Visualizing the endogenous distribution of elements within plant organs affords key insights in the regulation of trace elements in plants. Hyperaccumulators have extreme metal(loid) concentrations in their tissues, which make them useful models for studying metal(loid) homeostasis in plants. X-ray-based methods allow for the nondestructive analysis of most macro and trace elements with low limits of detection. However, observing the internal distributions of elements within plant organs still typically requires destructive sample preparation methods, including sectioning, for synchrotron X-ray fluorescence microscopy (XFM). X-ray fluorescence microscopy-computed tomography (XFM-CT) enables "virtual sectioning" of a sample thereby entirely avoiding artefacts arising from destructive sample preparation. The method can be used on frozen-hydrated samples, as such preserving "life-like" conditions. Absorption and Compton scattering maps obtained from synchrotron XFM-CT offer exquisite detail on structural features that can be used in concert with elemental data to interpret the results. In this article we introduce the technique and use it to reveal the internal distribution of hyperaccumulated elements in hyperaccumulator plant species. XFM-CT can be used to effectively probe the distribution of a range of different elements in plant tissues/organs, which has wide ranging applications across the plant sciences.

Correlative nano-imaging of metals and proteins in primary neurons by synchrotron X-ray fluorescence and STED super resolution microscopy: Experimental validation

BackgroundIt is becoming increasingly clear that biological metals such as iron, copper or zinc are involved in synaptic functions, and in particular in the mechanisms of synaptogenesis and subsequent plasticity. Understanding the role of metals on synaptic functions is a difficult challenge due to the very low concentration of these elements in neurons and to the submicrometer size of synaptic compartments. New methodTo address this challenge we have developed a correlative nano-imaging approach combining metal and protein detection. First, stimulated emission depletion (STED) microscopy, a super resolution optical microscopy technique, is applied to locate fluorescently labeled proteins. Then, synchrotron radiation induced X-ray fluorescence (SXRF) is performed on the same regions of interest, e.g. synaptic compartments. ResultsWe present here the principle scheme that allows this correlative nano-imaging and its experimental validation. We applied this correlative nano-imaging to the study of the physiological distribution of metals in synaptic compartments of primary rat hippocampal neurons. We thus compared the nanometric distribution of metals with that of synaptic proteins, such as PSD95 or cytoskeleton proteins. Comparison with existing method(s)Compared to correlative imaging approaches currently used to characterize synaptic structures, such as electron microscopy correlated with optical fluorescence, our approach allows for ultra-sensitive detection of trace metals using highly focused synchrotron radiation beams. ConclusionWe provide proof-of-principle for correlative imaging of metals and proteins at the synaptic scale and discuss the present limitations and future developments in this area.

Composite Structural Supercapacitors: High-Performance Carbon Nanotube Supercapacitors through Ionic Liquid Localisation.

Composite structural supercapacitors (SSC) are an attractive technology for aerospace vehicles; however, maintaining strength whilst adding energy storage to composite structures has been difficult. Here, SSCs were manufactured using aerospace-grade composite materials and CNT mat electrodes. A new design methodology was explored where the supercapacitor electrolyte was localised within the composite structure, achieving good electrochemical performance within the active region, whilst maintaining excellent mechanical performance elsewhere. The morphologies of these localised SSC designs were characterised with synchrotron X-ray fluorescence microscopy and synchrotron X-ray micro-computed tomography and could be directly correlated with both electrochemical and mechanical performance. One configuration used an ionogel with an ionic liquid (IL) electrolyte, which assisted localisation and achieved 2640 mW h kg−1 at 8.37 W kg−1 with a corresponding short beam shear (SBS) strength of 71.5 MPa in the active area. A separate configuration with only IL electrolyte achieved 758 mW h kg−1 at 7.87 W kg−1 with SBS strength of 106 MPa in the active area. Both configurations provide a combined energy and strength superior to results previously reported in the literature for composite SSCs.

Cellular-level distribution of manganese in Macadamia integrifolia, M. ternifolia, and M. tetraphylla from Australia.

Macadamia integrifolia and M. tetraphylla, unlike M. ternifolia, are known for their edible nuts. All three species over-accumulate the trace metal nutrient manganese (Mn) in their shoots. This study seeks to examine tissue- and cellular-level distribution of Mn and other plant nutrients in the three Macadamia species. The distribution of Mn, calcium, iron, and potassium were investigated in whole leaves and cross-sections of roots, petioles, and leaves using synchrotron-based X-ray fluorescence microscopy (XFM) in M. integrifolia, M. tetraphylla, and M. ternifolia. The results show Mn sequestration primarily in the leaf and midrib palisade mesophyll cells of all three species. Leaf interveinal regions, root cortical cells, and phloem cells were also found to be Mn loaded. The current study confirms earlier findings but further reveals that Mn is concentrated in the vacuoles of mesophyll cells owing to the exceptional resolution of the synchrotron XFM data, and the fact that fresh hydrated samples were used. New insights gained here into Mn compartmentalization in these highly Mn-tolerant Macadamias expand knowledge about potentially toxic over-accumulation of an essential micronutrient, which ultimately stands to inform strategies around farming edible species in particular.