Scanning X-ray Fluorescence Microscopy Research Articles

Effect of treatment conditions on the morphology of date empty fruit bunch lignocellulosic fiber for biocomposite applications

The fiber of the empty date fruit is one of the waste products left after the date fruit is harvested from the date palm. Optimization of the treatment parameters as well as the economics of the treatment process are critical to the successful commercialization of the treatment of natural fibers for the production of biocomposites. Of the natural fiber treatment methods described in previous work, hot water and alkali treatments are the most cost-effective, which justified the choice of these treatment methods in this work. Here, date empty fruit bunch fibers were pulverized to a particle size of 0–500 µm and then treated with boiling water at 100 °C for 3 h or with sodium hydroxide at different concentrations (2, 5, 10%) for 3 h at room temperature with constant stirring at 800 rpm. To confirm the effect of temperature on the fiber treatment, another fiber sample was treated at a 5% concentration of sodium hydroxide solution at an elevated temperature of 80 °C for the same period and stirring condition. The untreated and treated DEFB fibers were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), X-ray fluorescence (XRF), and scanning electron microscopy (SEM). Chemical analysis of the fibers showed that DEFB fiber treated with 5% sodium hydroxide solution at room temperature had the highest cellulose content (52.0%), which was also confirmed by the XRD analysis. The DEFB fiber treated with boiling water exhibited higher thermal stability while the sodium hydroxide-treated fiber exhibited higher crystallinity index and cellulose content. Apparently, DEFB fiber treated with sodium hydroxide solution at 5% concentration for 3 h at room temperature for continuous stirring at 800 rpm offered the best properties. The treated fibers are expected to be viable reinforcement in the production of biocomposites with the goal of achieving energy efficiency. The developed materials could be used in industrial applications such as insulating building systems, automotive parts, and home furniture.

Probing Reaction Heterogeneity in Thick Electrodes: LiFePO4 Versus LiNi0.6Mn0.2Co0.2O2

Introducing thick electrodes is a sound practice for increasing the energy density of lithium-ion batteries by minimizing the ratio of inactive components at device level. However, the inferior rate performance of the thick electrodes, which is believed to be caused by the inhomogeneous reaction, limits their further applications. In this study, we investigate the reaction distribution in LiFePO4 and LiNi0.6Mn0.2Co0.2O2 thick electrodes with combined scanning X-ray fluorescence (XRF) microscopy and X-ray absorption near edge structure (XANES) spectroscopy. 2D XRF-XANES imaging shows discharge reaction is highly non-uniform in the LFP electrode’s depth direction, the degree of which increases with the discharge rate. In contrast, NMC retains a uniform SOC distribution up to 1C (or 1.5C) rate. The XRF-XANES observations are verified by ToF-SIMS measurements. The different reaction distributions observed in LFP and NMC is explained by P2D modeling and has a thermodynamic origin Figure 1

Microstructural and Microbiological Properties of Peloids and Clay Materials from Lixouri (Kefalonia Island, Greece) Used in Pelotherapy

Clays have been applied for centuries by people for many uses. From pottery to medicine, clays and clay minerals constitute part of individuals’ daily routines. Natural fine-grained earth material, commonly found at Xi beach coastal area of Lixouri in Kefalonia island, was used during the last few decades by local people as well as from tourists for pelotherapy, even though this material has never been examined for its suitability for this use. This work was conducted aiming to characterize this material and determine if it is harmless and beneficial for therapeutic purposes or skin care. Field work revealed that the material is not homogenous and, therefore, some of its parts could be characterized as suitable, non-suitable or even harmful. The collected samples from Kefalonia were characterized according to their petrographic and chemical features using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF) and Transmission Electron Microscopy (TEM). Moreover, the microbial burden of the material was assessed analyzing the bacterial and fungi load. This study indicates that this geomaterial can be suitable for natural mud/peloid applications, but only in some parts of this area.

Zinc and iron dynamics in human islet amyloid polypeptide-induced diabetes mouse model

Metal homeostasis is tightly regulated in cells and organisms, and its disturbance is frequently observed in some diseases such as neurodegenerative diseases and metabolic disorders. Previous studies suggest that zinc and iron are necessary for the normal functions of pancreatic β cells. However, the distribution of elements in normal conditions and the pathophysiological significance of dysregulated elements in the islet in diabetic conditions have remained unclear. In this study, to investigate the dynamics of elements in the pancreatic islets of a diabetic mouse model expressing human islet amyloid polypeptide (hIAPP): hIAPP transgenic (hIAPP-Tg) mice, we performed imaging analysis of elements using synchrotron scanning X-ray fluorescence microscopy and quantitative analysis of elements using inductively coupled plasma mass spectrometry. We found that in the islets, zinc significantly decreased in the early stage of diabetes, while iron gradually decreased concurrently with the increase in blood glucose levels of hIAPP-Tg mice. Notably, when zinc and/or iron were decreased in the islets of hIAPP-Tg mice, dysregulation of glucose-stimulated mitochondrial respiration was observed. Our findings may contribute to clarifying the roles of zinc and iron in islet functions under pathophysiological diabetic conditions.

Vanadium Speciation in Ancient Shales Revealed through Synchrotron-Based X-ray Spectroscopy

Redox-sensitive trace elements, such as vanadium, are frequently used as paleoredox proxies to infer the redox status of ancient marine depositional environments. When applied to vanadium, this approach relies on an accurate understanding of vanadium geochemistry in marine sediments. This, in turn, requires the application of analytical techniques capable of providing reliable chemical information on vanadium host phases of vanadium and thus the ability to distinguish authigenic from detrital phases. The increasing availability of synchrotron-based X-ray spectroscopic techniques capable of providing chemical speciation information at both the bulk and micro-scale presents an opportunity to refine our understanding of vanadium geochemistry in ancient marine sediments. Here, we show the utility of synchrotron-based X-ray absorption near-edge structure (XANES) spectroscopy and scanning X-ray fluorescence microscopy (SXFM) for investigating vanadium host phases in ancient marine sediments. The studied samples from the 1400 Ma Xiamaling Formation came from strongly contrasting depositional settings (ranging from oxic to euxinic) with a wide range of vanadium enrichments (enrichment factors from 0.7 to 9.6), yet vanadium speciation determined by XANES was consistently found to be phyllosilicate-hosted vanadium (III). High-resolution elemental imaging by SXFM coupled with global statistical colocalization analyses revealed strong associations between vanadium and potassium, consistent with vanadium hosted by potassium-rich clay minerals. These findings, while demonstrating the power of synchrotron-based X-ray methods, imply that differentiating authigenic and detrital vanadium in ancient marine sediments is unlikely to be possible given that post-depositional processes result in similar chemical speciation for both fractions. This will also limit the reliability of vanadium isotope system studies that depend on differentiating authigenic and detrital fractions using selective extraction procedures.

Otoliths of marine fishes record evidence of low oxygen, temperature and pH conditions of deep Oxygen Minimum Zones

The deep-sea is rapidly losing oxygen, with profound implications for marine organisms. Within Eastern Boundary Upwelling Systems, such as the California and the Benguela Current Ecosystems, an important question is how the ongoing expansion, intensification and shoaling of Oxygen Minimum Zones (OMZs) will affect deep-sea fishes throughout their lifetimes. One of the first steps to filling this knowledge gap is through the development of tools and techniques to track fishes’ exposure to hypoxic (<45 μmol kg-1), low-temperature (∼4–10°C) and low-pH (∼7.5) waters when inhabiting OMZs. Here, we examine if the otoliths of deep-sea fishes living in OMZs exhibit distinct patterns of elemental and isotopic composition, which could be used to monitor their exposure history to severely hypoxic and low-pH waters. We hypothesize that the unique biogeochemistry of OMZs (i.e., low-oxygen, low-pH, and the presence of dissolved elements) will impart unique elemental and isotopic signatures upon the otoliths of both long-lived and short-lived deep-sea fishes living within it. We analyzed the otoliths of six deep-sea fish species from three OMZ regions: the Southern California Bight and the Gulf of California in the Northeast Pacific Ocean, and the Namibian shelf in the Southeast Atlantic Ocean. Three complementary techniques were applied: laser ablation inductively coupled plasma mass spectrometry, secondary ion mass spectrometry and scanning X-ray fluorescence microscopy. We observed that deep-water OMZ-dwelling fishes spanning a range of life-history traits (e.g., longevity, maximum size, growth rate, parental investment and thermal history inferred by δ18O) exhibited a common elemental fingerprint (with respect to Sr:Ca, Mn:Ca, Ba:Ca, Cu:Ca and Mg:Ca) when compared to a shallow-water marine fish from better-oxygenated waters. Our findings suggest that the underlying mechanism for the common elemental fingerprinting of otoliths of OMZ-dwelling fishes is attributed to the unique biogeochemistry found on the margins of these highly productive upwelling systems as well as the physiological constraints resident organisms are perennially exposed to, including low oxygen, pH and temperature conditions.

Life history strategies of Mekong pangasiid catfishes revealed by otolith microchemistry

Fourteen species of pangasiid catfish are found in the Mekong River. They are key components of both capture fisheries and aquaculture, although little is known about their migratory ecology, which is particularly important as some species are in decline. In order to examine the life-history strategies of key pangasiid catfishes in the Mekong River, we collected otoliths from 126 specimens belonging to four species in the Lower Mekong Basin. We analysed the otolith microchemical structure using two methods (Laser Ablation – Inductively Coupled Plasma Mass Spectrometry and Scanning X-ray Fluorescence Microscopy) to identify evidence of diadromy (movements between the ocean and upstream waters). We followed an established method of examining patterns of strontium to calcium (Sr:Ca) and barium to calcium (Ba:Ca) ratios along otolith transect profiles to interpret whether fish were in fresh or salt water at various stages of their life. We confirmed anadromy in two species (Pangasius krempfi and P. mekongensis; spawning in river but growing in marine waters) with at least three migratory tactics identified for each species, thus highlighting more diverse life history strategies than previously thought. Based on locations where we collected fish, we can infer these species migrate up to 700 km (P. mekongensis) and 1400 km (P. krempfi) from the sea into the Mekong River for spawning. The other two catfishes (P. elongatus and P. bocourti) appeared to be freshwater species that occasionally strayed into the estuary. Long-distance migratory species require free flowing rivers to connect critical habitats used at different life stages. Any activity disrupting these migratory pathways and disconnecting these habitats must be carefully considered. Conservation and management of transboundary species require international agreements to protect them from the impacts of river development, and the evidence presented here is pertinent for catfish in the Mekong River.

Synchrotron‐Based Nano‐X‐Ray Absorption Near‐Edge Structure Revealing Intracellular Heterogeneity of Iron Species in Magnetotactic Bacteria

Magnetotactic bacteria (MTB) sequester iron from the environment to biomineralize magnetite or greigite nanoparticles in magnetosome organelles, though the necessity of intracellular iron storage for the formation process is still in question. Understanding the role of iron storage would make clear the contribution of MTB in geochemical iron cycling and its potential importance during the biosynthesis of application‐relevant magnetic nanoparticles. Herein, how scanning X‐ray fluorescence microscopy (SXFM) and nanoscale X‐ray absorption near‐edge structure (nano‐XANES) mapping can spatially and chemically identify intracellular iron species is reported, creating an opportunity to examine the role of iron storage in magnetite biomineralization at the single‐cell level. Fe K‐edge nano‐XANES measurements of Magnetospirillum gryphiswaldense in varied iron media conditions and iron storage capacity reveal a significant quantity of intracellular iron heterogeneities through a distinction between formed magnetosomes and intracellular iron material. This intracellular iron component is found in both early and late stages of biomineralization. The capabilities of nano‐XANES in providing an experimental advantage in the multidisciplinary field of biomineralization are highlighted.

Development of scanning X-ray fluorescence microscope using KB mirror and white synchrotron radiation at SAGA Light Source

A scanning X-ray fluorescence microscope that uses a Kirkpatrick-Baez (KB) mirror and white synchrotron radiation (SR) was developed for obtaining detailed elemental maps within a micro-meter order. The KB mirror is a total reflection mirror, and the white X-rays are focused at a focus point without chromatic aberration. Therefore, the proposed microscope can use strong white and/or pink SR and enable elemental mapping within a practical measurement time at small synchrotron facilities. A feasibility study on the developed microscope was performed by using white SR at the SAGA Light Source in Tosu, Japan. By using the developed microscope, an X-ray microbeam 1 μm in diameter was successfully formed, and a fine elemental map of a Cu mesh and a seed of eustoma were obtained.

Nanofocused Scanning X-ray Fluorescence Microscopy Revealing an Effect of Heterozygous Hemoglobin S and C on Biochemical Activities in Plasmodium falciparum-Infected Erythrocytes.

While there is ample evidence suggesting that carriers of heterozygous hemoglobin S and C are protected from life-threatening malaria, little is known about the underlying biochemical mechanisms at the single cell level. Using nanofocused scanning X-ray fluorescence microscopy, we quantify the spatial distribution of individual elements in subcellular compartments, including Fe, S, P, Zn, and Cu, in Plasmodium falciparum-infected (P. falciparum-infected) erythrocytes carrying the wild type or variant hemoglobins. Our data indicate that heterozygous hemoglobin S and C significantly modulate biochemical reactions in parasitized erythrocytes, such as aberrant hemozoin mineralization and a delay in hemoglobin degradation. The label-free scanning X-ray fluorescence imaging has great potential to quantify the spatial distribution of elements in subcellular compartments of P. falciparum-infected erythrocytes and unravel the biochemical mechanisms underpinning disease and protective traits.

Unmasking continental natal homing in goliath catfish from the upper Amazon

Abstract Amazonian goliath catfishes are widespread in the Amazon Basin. Recently, otolith 87Sr:86Sr analyses using laser ablation–multi‐collector–inductively coupled plasma mass spectrometry (LA‐MC‐ICPMS) revealed a &gt;8,000 km trans‐Amazonian natal homing in Brachyplatystoma rousseauxii among fish caught and hatched in the largest Amazon River tributary, the upper Madeira basin. Although also suspected for fish in the upper Amazon, homing could not be demonstrated owing to less distinct environmental 87Sr:86Sr gradients along the Amazon mainstem. Using scanning X‐ray fluorescence microscopy (SXFM), a separate study provided evidence that Se:Ca and Sr:Ca are useful markers for identifying migration into Andean headwaters and the estuarine environment. We analysed otoliths of known 87Sr:86Sr profiles using SXFM mapping to test if Sr:Ca and Se:Ca patterns could demonstrate natal homing for three fish caught in the upper Amazon, using as reference two individuals that were natal homers and two forced residents (hatched after the construction of hydroelectric dams on the Madeira River) from the upper Madeira River. As hypothesised, although the Sr isotope profiles of the upper Amazon individuals were uninformative, two of them presented similar alternating mirror patterns of Sr:Ca and Se:Ca to those of the upper Madeira natal homers, indicating migrations out of the Andean region and into the estuary area. Both were therefore natal homers from the upper Amazon. The third individual from the upper Amazon presented similar Sr:Ca and Se:Ca patterns to those of the upper Madeira residents, suggesting it was a natural resident from the upper Amazon. By combining the results of 87Sr:86Sr analyses (LA‐MC‐ICPMS) and Sr:Ca and Se:Ca mappings (SXFM) that are completely independent of one another, we demonstrated that B. rousseauxii also performs natal homing in the upper Amazon. Our results indicate that the life cycle of B. rousseauxii is more complex than previous literature hypothesised, with the existence of partial migration, even in absence of physical barriers. Quantifying the relative importance of these different life‐history strategies will have important implications for fisheries management. Our results also lay the groundwork for conservation efforts in the context of hydropower development in the Amazon Basin and set testable hypotheses of the potential impacts of the Madeira River dams.

X-ray fluorescence imaging

Over the past two decades, numerous X-ray micro-beam studies have been published addressing the nondestructive investigation of chemical element distribution in condensed heterogeneous media. Based on this literature, some aspects of the field are discussed in this paper, including X-ray focusing methods and various elemental imaging techniques: scanning and confocal X-ray fluorescence microscopy, full-field X-ray fluorescence microscopy, X-ray fluorescence tomography, and prospects for combining X-ray fluorescence imaging with other physical methods rested on using synchrotron radiation.

Localized zinc distribution in shark vertebrae suggests differential deposition during ontogeny and across vertebral structures.

The development of shark vertebrae and the possible drivers of inter- and intra-specific differences in vertebral structure are poorly understood. Shark vertebrae are used to examine life-history traits related to trophic ecology, movement patterns, and the management of fisheries; a better understanding of their development would be beneficial to many fields of research that rely on these calcified structures. This study used Scanning X-ray Fluorescence Microscopy to observe zinc distribution within vertebrae of ten shark species from five different orders. Zinc was mostly localised within the intermedialis and was generally detected at levels an order of magnitude lower in the corpus calcareum. In most species, zinc concentrations were higher pre-birth mark, indicating a high rate of pre-natal zinc deposition. These results suggest there are inter-specific differences in elemental deposition within vertebrae. Since the deposition of zinc is physiologically-driven, these differences suggest that the processes of growth and deposition are potentially different in the intermedialis and corpus calcareum, and that caution should be taken when extrapolating information such as annual growth bands from one structure to the other. Together these results suggest that the high inter-specific variation in vertebral zinc deposition and associated physiologies may explain the varying effectiveness of ageing methodologies applied to elasmobranch vertebrae.

Quantitative X-ray fluorescence computed tomography for low-Z samples using an iterative absorption correction algorithm

X-ray fluorescence computed tomography is often used to measure trace element distributions within low-Z samples, using algorithms capable of X-ray absorption correction when sample self-absorption is not negligible. Its reconstruction is more complicated compared to transmission tomography, and therefore not widely used. We describe in this paper a very practical iterative method that uses widely available transmission tomography reconstruction software for fluorescence tomography. With this method, sample self-absorption can be corrected not only for the absorption within the measured layer but also for the absorption by material beyond that layer. By combining tomography with analysis for scanning X-ray fluorescence microscopy, absolute concentrations of trace elements can be obtained. By using widely shared software, we not only minimized the coding, took advantage of computing efficiency of fast Fourier transform in transmission tomography software, but also thereby accessed well-developed data processing tools coming with well-known and reliable software packages. The convergence of the iterations was also carefully studied for fluorescence of different attenuation lengths. As an example, fish eye lenses could provide valuable information about fish life-history and endured environmental conditions. Given the lens’s spherical shape and sometimes the short distance from sample to detector for detecting low concentration trace elements, its tomography data are affected by absorption related to material beyond the measured layer but can be reconstructed well with our method. Fish eye lens tomography results are compared with sliced lens 2D fluorescence mapping with good agreement, and with tomography providing better spatial resolution.

Generation of apodized X-ray illumination and its application to scanning and diffraction microscopy.

X-ray science has greatly benefited from the progress in X-ray optics. Advances in the design and the manufacturing techniques of X-ray optics are key to the success of various microscopic and spectroscopic techniques practiced today. Here the generation of apodized X-ray illumination using a two-stage deformable Kirkpatrick-Baez mirror system is presented. Such apodized illumination is marked by the suppression of the side-lobe intensities of the focused beam. Thus generated apodized illumination was employed to improve the image quality in scanning X-ray fluorescence microscopy. Imaging of a non-isolated object by coherent X-ray diffractive imaging with apodized illumination in a non-scanning mode is also presented.

Nuclear incorporation of iron during the eukaryotic cell cycle.

Scanning X-ray fluorescence microscopy has been used to probe the distribution of S, P and Fe within cell nuclei. Nuclei, which may have originated at different phases of the cell cycle, are found to show very different levels of Fe present with a strongly inhomogeneous distribution. P and S signals, presumably from DNA and associated nucleosomes, are high and relatively uniform across all the nuclei; these agree with X-ray phase contrast projection microscopy images of the same samples. Possible reasons for the Fe incorporation are discussed.

Imaging of intracellular fatty acids by scanning X-ray fluorescence microscopy.

Fatty acids are taken up by cells and incorporated into complex lipids such as neutral lipids and glycerophospholipids. Glycerophospholipids are major constituents of cellular membranes. More than 1000 molecular species of glycerophospholipids differ in their polar head groups and fatty acid compositions. They are related to cellular functions and diseases and have been well analyzed by mass spectrometry. However, intracellular imaging of fatty acids and glycerophospholipids has not been successful due to insufficient resolution using conventional methods. Here, we developed a method for labeling fatty acids with bromine (Br) and applied scanning X-ray fluorescence microscopy (SXFM) to obtain intracellular Br mapping data with submicrometer resolution. Mass spectrometry showed that cells took up Br-labeled fatty acids and metabolized them mainly into glycerophospholipids in CHO cells. Most Br signals observed by SXFM were in the perinuclear region. Higher resolution revealed a spot-like distribution of Br in the cytoplasm. The current method enabled successful visualization of intracellular Br-labeled fatty acids. Single-element labeling combined with SXFM technology facilitates the intracellular imaging of fatty acids, which provides a new tool to determine dynamic changes in fatty acids and their derivatives at the single-cell level.—Shimura, M., Shindou, H., Szyrwiel, L., Tokuoka, S. M., Hamano, F., Matsuyama, S., Okamoto, M., Matsunaga, A., Kita, Y., Ishizaka, Y., Yamauchi, K., Kohmura, Y., Lobinski, R., Shimizu, I., Shimizu, T. Imaging of intracellular fatty acids by scanning X-ray fluorescence microscopy.

Strontium mineralization of shark vertebrae.

Determining the age of sharks using vertebral banding is a vital component of management, but the causes of banding are not fully understood. Traditional shark ageing is based on fish otolith ageing methods where growth bands are assumed to result from varied seasonal calcification rates. Here we investigate these assumptions by mapping elemental distribution within the growth bands of vertebrae from six species of sharks representing four different taxonomic orders using scanning x-ray fluorescence microscopy. Traditional visual growth bands, determined with light microscopy, were more closely correlated to strontium than calcium in all species tested. Elemental distributions suggest that vertebral strontium bands may be related to environmental variations in salinity. These results highlight the requirement for a better understanding of shark movements, and their influence on vertebral development, if confidence in age estimates is to be improved. Analysis of shark vertebrae using similar strontium-focused elemental techniques, once validated for a given species, may allow more successful estimations of age on individuals with few or no visible vertebral bands.

A novel branched TAT(47-57) peptide for selective Ni(2+) introduction into the human fibrosarcoma cell nucleus.

A TAT47-57 peptide was modified on the N-terminus by elongation with a 2,3-diaminopropionic acid residue and then by coupling of two histidine residues on its N-atoms. This branched peptide could bind to Ni under physiological conditions as a 1 : 1 complex. We demonstrated that the complex was quantitatively taken up by human fibrosarcoma cells, in contrast to Ni(2+) ions. Ni localization (especially at the nuclei) was confirmed by imaging using both scanning X-ray fluorescence microscopy and Newport Green fluorescence. A competitive assay with Newport Green showed that the latter displaced the peptide ligand from the Ni-complex. Ni(2+) delivered as a complex with the designed peptide induced substantially more DNA damage than when introduced as a free ion. The availability of such a construct opens up the way to investigate the importance of the nucleus as a target for the cytotoxicity, genotoxicity or carcinogenicity of Ni(2+).

Scanning Hard X-ray Microscopy Imaging Modalities for Geobiological Samples

Modern scanning X-ray microscopy can help to unravel the spatial context between biotic and abiotic compounds of geobiological assemblies with the aim to finally link chemical pathways to biological activities at the nanometre scale. This work presents some multi-modal imaging techniques provided by hard X-ray microscopes at synchrotron radiation sources to address analytical needs in geobiological research. Using the examples of 1) a calcified basal skeleton of the demosponge Astrosclera willeyana, 2) an anaerobic methane-oxidizing microbial mat and 3) a bacterial sulfur-oxidizing consortium, we illustrate the potential of scanning X-ray fluorescence and scanning transmission X-ray microscopy, and a novel quantitative approach of ptychographic imaging at single cell level.