Synchrotron X-ray Fluorescence Research Articles

Multimodal synchrotron X-ray fluorescence imaging reveals elemental distribution in seeds and seedlings of the Zn-Cd-Ni hyperaccumulator Noccaea caerulescens.

The molecular biology and genetics of the Ni–Cd–Zn hyperaccumulator Noccaea caerulescens has been extensively studied, but no information is yet available on Ni and Zn redistribution and mobilization during seed germination. Due to the different physiological functions of these elements, and their associated transporter pathways, we expected differential tissue distribution and different modes of translocation of Ni and Zn during germination. This study used synchrotron X-ray fluorescence tomography techniques as well as planar elemental X-ray imaging to elucidate elemental (re)distribution at various stages of the germination process in contrasting accessions of N. caerulescens. The results show that Ni and Zn are both located primarily in the cotyledons of the emerging seedlings and Ni is highest in the ultramafic accessions (up to 0.15 wt%), whereas Zn is highest in the calamine accession (up to 600 μg g–1). The distribution of Ni and Zn in seeds was very similar, and neither element was translocated during germination. The Fe maps were especially useful to obtain spatial reference within the seeds, as it clearly marked the vasculature. This study shows how a multimodal combination of synchrotron techniques can be used to obtain powerful insights about the metal distribution in physically intact seeds and seedlings.

Insights Into Pulp Biomineralization in Human Teeth

IntroductionMineralized pulp (MP) compromises tooth function and its causation is unknown. The hypothesis of this study is that pulp mineralization is associated with pulpal tissue adaptation, increased mineral densities, and decreased permeabilities of tubular dentin and cementum. Methods will include correlative spatial mapping of physicochemical and biochemical characteristics of pulp, and contextualize these properties within the dentin-pulp complex (DPC) to reveal the inherent vunerabilities of pulp.MethodsSpecimens (N = 25) were scanned using micro X-ray computed tomography (micro-XCT) to visualize MP and measure mineral density (MD). Elemental spatial maps of MP were acquired using synchrotron X-ray fluorescence microprobe (μXRF) and energy dispersive X-ray spectroscopy (EDX). Extracted pulp tissues were sectioned for immunolabelling and the sections were imaged using a light microscope. Microscale morphologies and nanoscale ultrastructures of MP were imaged using scanning electron (SEM) and scanning transmission electron microscopy (STEM) techniques.ResultsHeterogeneous distribution of MD from 200 to 2,200 mg/cc, and an average MD of 892 (±407) mg/cc were observed. Highly mineralized pulp with increased number of occluded tubules, reduced pore diameter in cementum, and decreased connectivity in lateral channels were observed. H&E, trichrome, and von Kossa staining showed lower cell and collagen densities, and mineralized regions in pulp. The biomolecules osteopontin (OPN), osteocalcin (OCN), osterix (OSX), and bone sialoprotein (BSP) were immunolocalized around PGP 9.5 positive neurovascular bundles in MP. SEM and STEM revealed a wide range of nano/micro particulates in dentin tubules and spherulitic mineral aggregates in the collagen with intrafibrillar mineral surrounding neurovascular bundles. EDX and μXRF showed elevated counts of Ca, P, Mg, and Zn inside pulp and at the dentin-pulp interface (DPI) in the DPC.ConclusionColocalization of physical and chemical, and biomolecular compositions in MP suggest primary and secondary biomineralization pathways in pulp and dentin at a tissue level, and altered fluid dynamics at an organ level. Elevated counts of Zn at the mineralizing front in MP indicated its role in pulp biomineralization. These observations underpin the inherent mechano- and chemo-responsiveness of the neurovascular DPC and help elucidate the clinical subtleties related to pulpitis, dentin-bridge, and pulp stone formation.

Evidence for a Highly Cytokine‐Sensitive Network of Iron‐Associated Genes in Islets

Among the complex factors contributing to beta‐cell failure is inflammation. Elevated levels of proinflammatory cytokines in obese individuals, such as interleukin (IL)‐1beta and IL‐6, increases the risk of developing type‐2 diabetes (T2D), and there is evidence that these low levels of circulating cytokines lead to islet dysfunction. Iron is closely connected to both the inflammatory response and diabetes. High levels of dietary iron increase risk of developing T2D, and excessive iron uptake by beta‐cells can cause oxidative stress and inhibit function. In this study, islets were treated for 48h with 10 pg/mL IL‐1beta + 20 pg/mL IL‐6 as a model of low‐grade inflammation. Analysis of gene microarray data identified three iron‐associated genes among the most cytokine‐sensitive: HAMP, STEAP4, and LCN2. These proteins are all involved directly or indirectly with increasing and/or sequestering cellular iron. RT‐PCR following exposure to various stressors known to induce beta‐cell failure revealed upregulation of HAMP, STEAP4, and LCN2 to be cytokine‐specific. Overexpression of STEAP4 induced upregulation of HAMP and LCN2, while ferritin and ferroportin expression were unaffected. Beta‐cells scanned by synchrotron X‐Ray fluorescence provided data showing cytokine exposure alters iron distribution. Iron was found in discrete structures (area ~0.15‐0.45 µm2) that were significantly smaller and more iron‐dense in cytokine‐treated beta‐cells, consistent with the sequestering function of identified iron‐associated genes. These data suggest a network of iron‐regulating genes in beta‐cells plays a role in sequestering iron in response to low‐grade inflammation.

Natural nanoparticles of the critical element tellurium

Tellurium (Te) is a Critical Element that is toxic to microorganisms and humans alike, most notably in its soluble oxyanionic forms. To date, the biogeochemical behaviour of Te in Earth’s surface environment is largely unknown. Here, we report the discovery of elemental Te nanoparticles (Te NPs) in regolith samples using Single-Particle Inductively Coupled Plasma Mass Spectroscopy. Tellurium NPs were detected in both proximal and distal locations (bulk concentrations >4 ppm) relative to weathering Te ores. Synchrotron X-ray Fluorescence Mapping and X-ray Absorption Spectroscopy showed that bulk Te in the regolith is generally associated with Fe (oxyhydr)oxides and clay minerals, and mostly found in the oxidation states +IV and +VI. Although Te NPs account for less than 2 mol‰ of Te in our samples, their detection provides evidence for the active biogeochemical cycling of Te in surface environments. Te NPs are reactive and are likely to have formed in situ in distal samples, most likely via microbially-mediated reduction. Hence, the presence of Te NPs indicates the potential for release of toxic soluble forms of Te even in environments where most Te is “fixed” in forms such as Fe (oxyhydr)oxides that have low solubility and poor bioavailability.

In situ temperature measurements in sooting methane/air flames using synchrotron x-ray fluorescence of seeded krypton atoms.

Synchrotron x-ray fluorescence has been used to measure temperatures in optically dense gases where traditional methods would fail. These data provide a benchmark for stringent tests of computational fluid dynamics models for complex systems where physical and chemical processes are intimately linked. The experiments measured krypton number densities in a sooting, atmospheric pressure, nonpremixed coflow flame that is widely used in combustion research. The experiments not only form targets for the models, but the simulations also identify potential sources of uncertainties in the measurements, allowing for future improvements.

Contrasting patterns of nickel distribution in the hyperaccumulators Phyllanthus balgooyi and Phyllanthus rufuschaneyi from Malaysian Borneo.

Globally, the majority of Ni hyperaccumulator plants occur on ultramafic soils in tropical regions, and the genus Phyllanthus, from the Phyllanthaceae family, is globally the most represented taxonomical group. Two species from Sabah (Malaysia) are remarkable because Phyllanthus balgooyi can attain >16 wt% of Ni in its phloem exudate, while Phyllanthus rufuschaneyi reaches foliar concentrations of up to 3.5 wt% Ni, which are amongst the most extreme concentrations of Ni in any plant tissue. Synchrotron X-ray fluorescence microscopy, nuclear microbe (micro-PIXE+BS) and (cryo) scanning electron microscopy with energy dispersive spectroscopy were used to spatially resolve the elemental distribution in the plant organs of P. balgooyi and P. rufuschaneyi. The results show that P. balgooyi has extraordinary enrichment of Ni in the (secondary) veins of the leaves, whereas in contrast, in P. rufuschaneyi Ni occurs in interveinal areas. In the roots and stems, Ni is localized mainly in the cortex and phloem but is much lower in the xylem. The findings of this study show that, even within the same genus, the distribution of nickel and other elements, and inferred processes involved with metal hyperaccumulation, can differ substantially between species.

Altering the localization and toxicity of arsenic in rice grain

Previous work has shown that inorganic As localizes in rice bran whereas DMA localizes in the endosperm, but less is known about co-localization of As and S species and how they are affected by growing conditions. We used high-resolution synchrotron X-ray fluorescence imaging to image As and S species in rice grain from plants grown to maturity in soil (field and pot) and hydroponically (DMA or arsenite dosed) at field-relevant As concentrations. In hydroponics, arsenite was localized in the ovular vascular trace (OVT) and the bran while DMA permeated the endosperm and was absent from the OVT in all grains analyzed, and As species had no affect on S species. In pot studies, soil amended with Si-rich rice husk with higher DMA shifted grain As into the endosperm for both japonica and indica ecotypes. In field-grown rice from low-As soil, As localized in the OVT as arsenite glutathione, arsenite, and DMA. Results support a circumferential model of grain filling for arsenite and DMA and show Si-rich soil amendments alter grain As localization, potentially lessening risk to rice consumers.

Sr distribution as proxy for Ca distribution at depth in SXRF analysis of mm‐sized carbonaceous chondrites: Implications for asteroid sample return missions

AbstractReliable identification of chondrules, calcium‐aluminum‐rich inclusions (CAIs), carbonate grains, and Ca‐phosphate grains at depth within untouched, unprepared chondritic samples by a nondestructive analytical method, such as synchrotron X‐ray fluorescence (SXRF) computed tomography (CT), is an essential first step before intrusive analytical and sample preparation methods are performed. The detection of a local Ca‐enrichment could indicate the presence of such a component, all of which contain Ca as major element and/or Ca‐bearing minerals, allowing it to be precisely located at depth within a sample. However, the depth limitation from which Ca‐K fluorescence can travel through a chondrite sample (e.g., ∼115 µm through material of 1.5 g cm−3) to XRF detectors leaves many Ca‐bearing components undetected at deeper depths. In comparison, Sr‐K lines travel much greater distances (∼1700 µm) through the same sample density and are, thus, detected from much greater depths. Here, we demonstrate a clear, positive, and preferential correlation between Ca and Sr and conclude that Sr‐detection can be used as proxy for the presence of Ca (and, thus, Ca‐bearing components) throughout mm‐sized samples of carbonaceous chondritic material. This has valuable implications, especially for sample return missions from carbonaceous C‐type asteroids, such as Ryugu or Bennu. Reliable localization, identification, and targeted analysis by SXRF of Ca‐bearing chondrules, CAIs, and carbonates at depth within untouched, unprepared samples in the initial stages of a multianalysis investigation insures the valuable information they hold of pre‐ and post‐accretion processes in the early solar system is neither corrupted nor destroyed in subsequent processing and analyses.

Targeted Positioning of Quantum Dots Inside 3D Silicon Photonic Crystals Revealed by Synchrotron X-ray Fluorescence Tomography.

It is a major outstanding goal in nanotechnology to precisely position functional nanoparticles, such as quantum dots, inside a three-dimensional (3D) nanostructure in order to realize innovative functions. Once the 3D positioning is performed, the challenge arises how to nondestructively verify where the nanoparticles reside in the 3D nanostructure. Here, we study 3D photonic band gap crystals made of Si that are infiltrated with PbS nanocrystal quantum dots. The nanocrystals are covalently bonded to polymer brush layers that are grafted to the Si–air interfaces inside the 3D nanostructure using surface-initiated atom transfer radical polymerization (SI-ATRP). The functionalized 3D nanostructures are probed by synchrotron X-ray fluorescence (SXRF) tomography that is performed at 17 keV photon energy to obtain large penetration depths and efficient excitation of the elements of interest. Spatial projection maps were obtained followed by tomographic reconstruction to obtain the 3D atom density distribution with 50 nm voxel size for all chemical elements probed: Cl, Cr, Cu, Ga, Br, and Pb. The quantum dots are found to be positioned inside the 3D nanostructure, and their positions correlate with the positions of elements characteristic of the polymer brush layer and the ATRP initiator. We conclude that X-ray fluorescence tomography is very well suited to nondestructively characterize 3D nanomaterials with photonic and other functionalities.

Preservation of Terrestrial Microorganisms and Organics Within Alteration Products of Chondritic Meteorites from the Nullarbor Plain, Australia.

Meteorites that fall to Earth quickly become contaminated with terrestrial microorganisms. These meteorites are out of chemical equilibrium in the environments where they fall, and equilibration promotes formation of low-temperature alteration minerals that can entomb contaminant microorganisms and thus preserve them as microfossils. Given the well-understood chemistry of meteorites and their recent discovery on Mars by rovers, a similarly weathered meteorite on Mars could preserve organic and fossil evidence of a putative past biosphere at the martian surface. Here, we used several techniques to assess the potential of alteration minerals to preserve microfossils and biogenic organics in terrestrially weathered ordinary chondrites from the Nullarbor Plain, Australia. We used acid etching of ordinary chondrites to reveal entombed fungal hyphae, modern biofilms, and diatoms within alteration minerals. We employed synchrotron X-ray fluorescence microscopy of alteration mineral veins to map the distribution of redox-sensitive elements of relevance to chemolithotrophic organisms, such as Mn-cycling bacteria. We assessed the biogenicity of fungal hyphae within alteration veins using a combination of Fourier-transform infrared spectroscopy and pyrolysis gas chromatography-mass spectrometry, which showed that alteration minerals sequester and preserve organic molecules at various levels of decomposition. Our combined analyses results show that fossil microorganisms and the organic molecules they produce are preserved within calcite-gypsum admixtures in meteorites. Furthermore, the distributions of redox-sensitive elements (e.g., Mn) within alteration minerals are localized, which qualitatively suggests that climatically or microbially facilitated element mobilization occurred during the meteorite's residency on Earth. If returned as part of a sample suite from the martian surface, ordinary chondrites could preserve similar, recognizable evidence of putative past life and/or environmental change.

In Situ X-ray Fluorescence Evaluation of Metal Ion Adsorption on Ferric Oxyhydroxide in Frozen Solutions

Cryosphere plays an important role in the global circulation of various chemical substances through the chemical processes that occur therein. Metal ions are adsorbed on adsorbents, such as ferric (oxy)hydroxides (FeOxH) and iron manganese oxides, and can be accumulated in the frozen phases. The metal ions can be supplied from the cryosphere to the hydrosphere in the bioavailable form by the desorption of metal ions during ice melting. Therefore, quantitative evaluation of the adsorption of metal ions in the frozen state is important to understand their exchange between the frozen and solution phases. Here, we propose in situ synchrotron X-ray fluorescence (XRF) as an appropriate method to quantitatively measure the adsorption of metal ions on FeOxH in a frozen solution. When NaCl solution freezes, a freeze-concentrated solution (FCS) is separated from ice. XRF imaging confirms that the first-row transition metal ions, that is, Mn2+, Co2+, Cu2+, and Zn2+, are enriched with FeOxH in the FCS. While in the presence of tris(hydroxymethyl)aminomethane (tris), Cu2+ forms a stable tris-complex and does not adsorb on FeOxH, other metal ions are partially adsorbed on FeOxH. Therefore, Cu2+ is always dissolved in the FCS, but other metal ions are distributed in both FCS and FeOxH. The linear correlations between the normalized XRF intensity of Cu2+ and those of other metal ions dissolved in the FCS are confirmed. Also, the normalized XRF intensity of Fe in FeOxH is proportional to those of the adsorbed metal ions. Thus, the XRF signals of Cu and Fe are considered to represent the other metal ions contained in the FCS and those adsorbed on FeOxH, respectively. The multivariate regression analysis provides the relative contributions of these two different states of the metal ion in frozen samples. From the regression coefficients, the adsorption ratio of the metal ion in the frozen phase can be estimated. The time change in the adsorption ratio is also successfully evaluated using this method.

A bimodal probe for fluorescence and synchrotron X-ray fluorescence imaging of dopaminergic neurons in the brain.

A bimodal probe, the erythrosine B (EB) conjugated immunoglobulin G complex (EB/IgG), has been developed for the fluorescence and synchrotron X-ray fluorescence (SXRF) imaging of dopaminergic neurons in the brain.

Nickel distribution in

Context Hyperaccumulator plants are of considerable interest for their extreme physiology. Stackhousia tryonii is a nickel (Ni) hyperaccumulator plant endemic to ultramafic outcrops in Queensland (Australia) capable of attaining up to 41 300 μg g−1 foliar Ni. Aims This study sought to elucidate the distribution of Ni in S. tryonii by using synchrotron X-ray fluorescence micro-computed tomography (XFM-CT), complemented with elemental maps acquired from physically sectioned plant organs. Its Ni-enriched cylindrical photosynthetic stems make them particularly well suited samples for synchrotron XFM-CT. Methods XFM-CT enables ‘virtual sectioning’ of a sample, avoiding artefacts arising from physical sample preparation. The method can be used on fresh samples that are frozen during the analysis, which preserves ‘life-like’ conditions by limiting radiation damage. It also prevents/minimises other artefacts. Key results The results showed that Ni is mainly concentrated in the apoplastic space surrounding epidermal cells, and in some epidermal cell vacuoles. This finding is significant because this ‘free’ solute Ni is likely to be lost during physical sectioning. Conclusions and implications This case study has highlighted the utility of the XFM-CT approach for visualising metals within intact plant organs, which may be used across the plant sciences.

Core characterisation and predicted CO2 reactivity of sandstones and mudstones from an Australian oil field

CO2 geological storage has been proposed as one method to mitigate climate change. Storage of CO2 in depleted oil or gas fields is one option, potentially following enhanced recovery. Understanding the potential impacts of CO2 water rock reactions is an important aspect of storage feasibility studies. Drill core samples of sandstones and mudstones from the Jurassic Moonie oil field, Australia, were characterised. In the Precipice Sandstone reservoir samples pore throats had broad size distributions, with mercury intrusion porosities 6.2 to 14.6%. Evergreen Formation samples were more variable with 1.2 to 16.1% porosity. Porosities measured by QEMSCAN were in reasonable agreement at 8.6 to 15.3% for Precipice Sandstones, and 0.6 to 21.5 for the Evergreen Formation. Sandstones had larger pore throat sizes and lower threshold pressures indicative of good reservoir rocks. Calcite cemented sandstones had truncated pore throat distributions, and the coal and clay rich mudstones had pore throats <0.1 μm with higher threshold pressures likely to seal or baffle CO2. Quartz grains were naturally fractured, with silica, apatite, rutile, calcite, and siderite cements filling porosity in some samples. Feldspars had been weathered producing secondary porosity but also resulting in kaolinite and illite filling intergranular porosity. Pyrite and barite were mainly associated with coals. Synchrotron X-ray fluorescence mapping showed Sr was mainly hosted in calcite cement, apatite and barite; with Rb in both plagioclase and K-feldspars. Calcite mainly hosted Mn; while Zn and Cu were mainly in sulphides. Sulphide minerals in coal also hosted As in one core. Kinetic geochemical CO2-water-rock modelling using the characterisation data over 30 or 1000 years indicated reaction of carbonate minerals where present, and alteration of mainly plagioclase, K-feldspar and chlorite. Net precipitation of ankerite, calcite or siderite mineral trapped 0.23 to 1.28 kg/m3 of CO2 after 1000 years in the different rock packages and was highest in Evergreen Formation rocks. The predicted pH was in the range 5.0 to 5.4 after 1000 years, or higher at 5.2 to 7.1 in lower CO2 fugacity models. Sandstone reactivity was overall low over 30 years indicating a low likelihood of reservoir scaling which would be favourable, with mineral trapping likely in the overlying Evergreen Formation.

Imaging the structural organization of chemical elements in growth cones of developing hippocampal neurons.

During neurodevelopment, neurons form growth cones, F-actin rich extensions located at the distal end of the neurites. Growth cones allow dendrites and axons to build synaptic connections through a process of neurite guidance whose mechanisms have not been fully elucidated. Calcium is an important element in this process by inducing F-actin reorganization. We hypothesized that other biologically active elements might be involved in the growth cone-mediated neurite guidance mechanisms. We performed super resolution and confocal microscopy of F-actin, followed by synchrotron X-ray fluorescence microscopy of phosphorous, sulfur, chlorine, potassium, calcium, iron and zinc on growth cones from primary rat hippocampal neurons. We identified two main patterns of element organization. First, active growth cones presenting an asymmetric distribution of Ca co-localized with the cytoskeleton protein F-actin. In active growth cones, we found that the distributions of P, S, Cl, K, and Zn are correlated with Ca. This correlation is lost in the second pattern, quiescent growth cones, exhibiting a spread elemental distribution. These results suggest that Ca is not the only element required in the F-actin rich active regions of growth cones. In addition, highly concentrated Fe spots of submicrometer size were observed in calcium-rich areas of active growth cones. These results reveal the need for biological active elements in growth cones during neural development and may help explain why early life deficiencies of elements, such as Fe or Zn, induce learning and memory deficits in children.

High energy synchrotron X-ray fluorescence trace element study of a millimeter-sized asteroidal particle in preparation for the Hayabusa2 return sample analyses

The trace element content and distribution - including rare Earth elements (REEs) - measured in mm-sized asteroidal samples returned by JAXA's Hayabusa2 mission are important chemical parameters to decipher asteroid Ryugu's chronology of formation linked to early Solar System processes. In order to identify and analyze ancient Solar Nebula components, such as calcium‑aluminum-rich inclusions (CAIs), by their trace element and REE content, a synchrotron beam with an incident energy of 90 keV is used to optimize the XRF signal and increase the information depth in the sample. The application of a (sub-)microscopic X-ray beam with such a high excitation energy not only allows for the detection of a wide range of heavy elements, but also to study their 3-dimensional distribution in mm-sized samples by means of X-ray fluorescence computed tomography (XRF-CT). The experiment was performed in anticipation of the initial analysis of the Hayabusa2 return samples at beamline ID15a of the European Synchrotron Radiation Facility (ESRF), Grenoble, France. The samples were analyzed with a focused beam of 0.5 × 0.5 μm2, achieving limit of detection values as low as 0.5 ppm with an acquisition time of 1 s. Here we present results of scanning XRF(-CT) analysis of a mm-sized sample of the Murchison meteorite, a Mighei type chondrite (CM2), wherein a 9.6 × 11.5 × 8.2 μm3 CAI phase was detected and analyzed. The CAI grain is shown to be detectable throughout the entire sample volume (~700 μm) during an XRF-CT scan over a full 360° angular range, thus proving the applicability of the method to study the microscopic distribution of high-Z elements at trace level concentration within millimeter-sized asteroidal particles.

Copper and Trace Elements in Gallbladder form Patients with Wilson's Disease Imaged and Determined by Synchrotron X-ray Fluorescence.

Investigations about suspected tissue alterations and the role of gallbladder in Wilson’s disease (WD)—an inherited genetic disease with impaired copper metabolism—are rare. Therefore, tissue from patients with genetically characterised WD was investigated by microscopic synchrotron X-ray fluorescence (µSRXRF). For two-dimensional imaging and quantification of elements, X-ray spectra were peak-fitted, and the net peak intensities were normalised to the intensity of the incoming monochromatic beam intensity. Concentrations were calculated by fundamental parameter-based program quant and external standardisation. Copper (Cu), zinc (Zn) and iron (Fe) along with sulphur (S) and phosphorus (P) mappings could be demonstrated in a near histological resolution. All these elements were increased compared to gallbladder tissue from controls. Cu and Zn and Fe in WD-GB were mostly found to be enhanced in the epithelium. We documented a significant linear relationship with Cu, Zn and sulphur. Concentrations of Cu/Zn were roughly 1:1 while S/Cu was about 100:1, depending on the selected areas for investigation. The significant linear relationship with Cu, Zn and sulphur let us assume that metallothioneins, which are sulphur-rich proteins, are increased too. Our data let us suggest that the WD gallbladder is the first in the gastrointestinal tract to reabsorb metals to prevent oxidative damage caused by metal toxicity.

Extreme-resolution synchrotron X-Ray fluorescence mapping of ore samples

In order to maximise profit and sustainability of a mining operation, knowledge of the chemistry, mineralogy, texture, and structure of the ore is essential. Continuous advancements in analytical techniques enable studying these features with increasing detail. Synchrotron radiation X-ray fluorescence is unparalleled in its simultaneously high spatial resolution and detection range. Yet, its application in ore geology research and the mining industry is still in its infancy. This study investigated opportunities of extreme-resolution synchrotron X-ray fluorescence mapping of ore samples. Analysis was performed at the NanoMAX beamline at the MAX IV synchrotron facility in Lund, Sweden. The samples investigated are from the Liikavaara Östra Cu-(W-Au) deposit, northern Sweden. Analysis covered areas of several hundreds of μm2 in grains of molybdenite, pyrite, and native Bi. Key results included successful mapping of the lattice-bound distribution of Re, Se, and W in molybdenite at 200 nm spot/step size and detection of nanometre inclusions of Au in native Bi at 50 nm spot/step size. Challenges were encountered concerning data acquisition and processing. In order to achieve satisfactory resolution of both light and heavy elements and to limit mapping artefacts, repeated scans of the same area with varied experimental parameters and very thin (quasi-2d) samples are required. For complex geological samples, the software used for analysing spectral data (PyMCA) requires a considerable degree of human examination, which may be a source of error. Overall, synchrotron X-ray fluorescence mapping has a strong analytical potential for ore geology research, in analysing and imaging trace elements that would constitute potential by-products in mining operations. Detailed knowledge of how trace elements occur in the ores will inform the development of appropriate metal extraction programs thus ensuring that a larger part of the ore may then be utilized.

Distribution of Pb and Se in mouse brain following subchronic Pb exposure by using synchrotron X-ray fluorescence

Lead (Pb) is a well-known neurotoxicant and environmental hazard. Recent experimental evidence has linked Pb exposure with neurological deterioration leading to neurodegenerative diseases, such as Alzheimer’s disease. To understand brain regional distribution of Pb and its interaction with other metal ions, we used synchrotron micro-x-ray fluorescence technique (μ-XRF) to map the metal distribution pattern and to quantify metal concentrations in mouse brains. Lead-exposed mice received oral gavage of Pb acetate once daily for 4 weeks; the control mice received sodium acetate. Brain tissues were cut into slices and subjected for analysis. Synchrotron μ-XRF scans were run on the PETRA III P06 beamline (DESY). Coarse scans of the entire brain were performed to locate the cortex and hippocampus, after which scans with higher resolution were run in these areas. The results showed that: a) the total Pb intensity in Pb-exposed brain slices was significantly higher than in control brain; b) Pb typically deposited in localized particles of <10 um2 in both the Pb-exposed and control brain slices, with more of these particles in Pb-exposed samples; c) selenium (Se) was significantly correlated with Pb in these particles in the cortex and hippocampus/corpus callosum regions in the Pb-exposed samples, and the molar ratio of the Se and Pb in these particles is close to 1:1. These results indicated that Se may play a crucial role in Pb-induced neurotoxicity. Our findings call for further studies to investigate the relationship between Pb exposure and possible Se detoxification responses, and the implication in the etiology of Alzheimer’s disease.

On 2D-FTIR-XRF microscopy – A step forward correlative tissue studies by infrared and hard X-ray radiation

Correlative Fourier Transform Infra-Red (FTIR) and hard X-Ray Fluorescence (XRF) microscopy studies of thin biological samples have recently evolved as complementary methods for biochemical fingerprinting of animal/human tissues. These are seen particularly useful for tracking the mechanisms of neurological diseases, i.e., in Alzheimer/Parkinson disease, in the brain where mishandling of trace metals (Fe, Cu, Zn) seems to be often associated with ongoing damage to molecular components via, among others, oxidative/reductive stress neurotoxicity. Despite substantial progress in state-of-the-art detection and data analysis methods, combined FTIR-XRF experiments have never benefited from correlation and co-localization analysis of molecular moieties and chemical elements, respectively. We here propose for the first time a completely novel data analysis pipeline, utilizing the idea of 2D correlation spectrometry for brain tissue analysis. In this paper, we utilized combined benchtop FTIR - synchrotron XRF mapping experiments on thin brain samples mounted on polypropylene membranes. By implementing our recently developed Multiple Linear Regression Multi-Reference (MLR-MR) algorithm, along with advanced image processing, artifact-free 2D FTIR-XRF spectra could be obtained by mitigating the impact of spectral artifacts, such as Etalon fringes and mild scattering Mie-like signatures, in the FTIR data. We demonstrated that the method is a powerful tool for co-localizing and correlating molecular arrangements and chemical elements (and vice versa) using visually attractive 2D correlograms. Moreover, the methods’ applicability for fostering the identification of distinct (biological) materials, involving chemical elements and molecular arrangements, is also shown. Taken together, the 2D FTIR-XRF method opens up for new measures for in-situ investigating hidden complex biochemical correlations, and yet unraveled mechanisms in a biological sample. This step seems crucial for developing new strategies for facilitating the research on the interaction of metals/nonmetals with organic components. This is particularly important for enhancing our understanding of the diseases associated with metal/nonmetal mishandling.