The effect of a dam on the copper accumulation in estuarine sediment and associated nematodes in a Mekong estuary.

Dam construction across the main flow of an estuary can greatly contribute to a high accumulation of inorganic contaminants. However, it remains unknown to what extend externally available heavy metals are incorporated into biota living in those contaminated environments. In this study, the heavy metal copper was investigated both in the sediment and in the tissues of nematodes taken from the subtidal zone in the Ba Lai estuary where a dam is present, and compared with samples from the dam-free Ham Luong estuary, both part of the Mekong Delta. Samples were taken in the dry season of 2017 in four stations in the Ba Lai estuary with two stations in the downstream part from the dam and two upstream. Similar locations with respect to the distance were sampled in the dam-free estuary. The internal copper concentration in nematodes was measured by applying micro X-ray fluorescence. The results showed that both internal and sediment copper concentrations were different between the two estuaries and among estuarine sections. The highest copper concentration in nematodes was found in the upstream section of Ba Lai estuary where the greatest accumulation of sedimentary copper was observed, while the dammed downstream part was lowest in internal copper accumulation. Moreover, there was more variation in the copper levels between the two sections within the dammed estuary compared to those in Ham Luong. These observations might point to the contribution of the Ba Lai dam to the increase of copper contaminants in the benthic environment leading to accumulation in nematodes.

Monte Carlo Simulation Aided Quantitative Laboratory X-ray Fluorescence Analysis and Its Application in Provenancing Studies for Geo-Archeological Samples.

A laboratory-based X-ray fluorescence (XRF) methodology is presented for standardless quantified analysis based on a monochromatic X-ray spectrometer coupled to Monte Carlo aided quantification. This procedure will be valuable for many scientific fields (e.g. archaeology, geology, etc.) where the unique nature of the investigated samples calls for the application of non-destructive techniques. To illustrate the value of the methodology, a case study is presented where flint artefacts from the Scheldt basin are analyzed in an attempt to provenance them. So far, little geochemical research has been done in this area. Our results contribute to the creation of a database that will help assign lithic artefacts to specific geological outcrops and will aid further research in this field.

Quantitative Reconstruction of Polychromatic X-ray Fluorescence Computed Tomography Using Transmission Tomography.

Through measuring the intensity of the fluorescence X-rays emitted by the elements of interest, X-ray fluorescence computed tomography (XFCT) is capable of mapping the elemental distribution inside an object without destructively sectioning it. With the recent advances in XFCT utilizing polychromatic microfocus X-ray sources, it is expected that the popularity of such imaging modality will rise further. However, XFCT suffers from self-absorption effects, which make it challenging to reconstruct the elemental distribution inside the sample accurately. For this reason, polychromatic XFCT is mainly used to retrieve the distribution of elements with a relatively high atomic number (Z) when compared to the matrix of the sample. To enable the quantitative reconstruction of trace and low Z elements with polychromatic XFCT, a novel reconstruction method has been proposed in this manuscript. Through examining the proposed method on both simulation data and experimental data, its capacity on retrieving the density distribution of relatively low Z elements has been confirmed.

Dynamic performance of a fungal biofilter packed with perlite for the abatement of hexane polluted gas streams using SIFT-MS and packing characterization with advanced X-ray spectroscopy.

The use of Fusarium solani fungi in an expanded perlite packed biofilter was investigated for the treatment of a hexane polluted waste gas stream using selected ion flow tube mass spectrometry (SIFT-MS). The latter analytical technique proved to be of utmost importance to evaluate the performance of the biofilter at high time resolution (seconds) under various transient conditions, analogous to industrial situations. The biofilter was operational for 277 days with inlet loads varying between 1 and 14 g m-3 h-1 and applying an empty bed residence time of 116 s. The results showed a positive behaviour of the biofilter against different types of disruptions such as: (i) changes in the relative humidity of the inlet gas, (ii) stopping the carbon supply for 1, 5 and 10 days, (iii) varying the inlet hexane concentration (step increases and intermittent pulses) and (iv) limiting the availability of nutrients. X-ray imaging (both conventional 2D µCT and X-ray fluorescence, XRF) was applied for the first time on biofilter media in order to get insight in the internal structure of expanded perlite and to visualise the biomass growth. The latter in combination with online porosity measurements using SIFT-MS provides fundamental information regarding the biofiltration process.

Correlations between As in Earthworms' Coelomic Fluid and As Bioavailability in Highly Polluted Soils as Revealed by Combined Laboratory X-ray Techniques.

Combined X-ray-based spectroscopy techniques were applied to investigate arsenic (As) bioaccumulation in earthworms (Eisenia andrei) exposed to six field-collected polluted soils (58-13 330 mg As kg-1). After 14 days of exposure to the arsenious soils, the As distribution in earthworms was examined by micro-X-ray fluorescence spectroscopy (µXRF), after epoxy resin embedding and preparing thin sections. Similar to µXRF data, XRF-computed tomography (XRF-CT) confirmed As accumulation in the coelom of intact earthworms. Therefore, total-reflection XRF was used to determine total As within both the whole earthworm's body (AsE) and coelomic fluid extracts (AsF). Bioaccumulation data (AsE and AsF) were thereafter evaluated in relation to total As concentration in soils (AsT) and to As mobile fraction in soils. A significant linear correlation (R2 = 0.97) was found between AsE and AsF, indicating that the As sequestrated into the coelomic fluid may reflect the total body concentration. Therefore, we may conclude that the As concentration in the coelomic fluid can be used as an index of As availability. This paper demonstrates that by combining different laboratory X-ray analytical techniques, compartmentalization and bioavailability of potentially toxic elements can be visualized and quantified within indicator-living organisms, thus contributing to an improved risk assessment for contaminated soils.

Correction to: Three-dimensional reconstruction of the distribution of elemental tags in single cells using laser ablation ICP-mass spectrometry via registration approaches.

The authors would like to call the reader's attention to the fact that unfortunately the originally provided affiliation for Dr. Tomoko Asaoka was not correct.

Three-dimensional reconstruction of the distribution of elemental tags in single cells using laser ablation ICP-mass spectrometry via registration approaches.

This paper describes a workflow towards the reconstruction of the three-dimensional elemental distribution profile within human cervical carcinoma cells (HeLa), at a spatial resolution down to 1 µm, employing state-of-the-art laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) instrumentation. The suspended cells underwent a series of fixation/embedding protocols and were stained with uranyl acetate and an Ir-based DNA intercalator. A priori, laboratory-based absorption micro-computed tomography (µ-CT) was applied to acquire a reference frame of the morphology of the cells and their spatial distribution before sectioning. After CT analysis, a trimmed 300 × 300 × 300 µm3 block was sectioned into a sequential series of 132 sections with a thickness of 2 µm, which were subjected to LA-ICP-MS imaging. A pixel acquisition rate of 250 pixels s-1 was achieved, through a bidirectional scanning strategy. After acquisition, the two-dimensional elemental images were reconstructed using the timestamps in the laser log file. The synchronization of the data required an improved optimization algorithm, which forces the pixels of scans in different ablation directions to be spatially coherent in the direction orthogonal to the scan direction. The volume was reconstructed using multiple registration approaches. Registration using the section outline itself as a fiducial marker resulted into a volume which was in good agreement with the morphology visualized in the µ-CT volume. The 3D µ-CT volume could be registered to the LA-ICP-MS volume, consisting of 2.9 × 107 voxels, and the nucleus dimensions in 3D space could be derived.

Nanoscopic X-ray fluorescence imaging and quantification of intracellular key-elements in cryofrozen Friedreich's ataxia fibroblasts.

Synchrotron radiation based nanoscopic X-ray fluorescence (SR nano-XRF) analysis can visualize trace level elemental distribution in a fully quantitative manner within single cells. However, in-air XRF analysis requires chemical fixation modifying the cell's chemical composition. Here, we describe first nanoscopic XRF analysis upon cryogenically frozen (-150°C) fibroblasts at the ID16A-NI 'Nano-imaging' end-station located at the European Synchrotron Radiation Facility (ESRF) in Grenoble (France). Fibroblast cells were obtained from skin biopsies from control and Friedreich's ataxia (FRDA) patients. FRDA is an autosomal recessive disorder with dysregulation of iron metabolism as a key feature. By means of the X-ray Fundamental Parameter (FP) method, including absorption correction of the ice layer deposited onto the fibroblasts, background-corrected mass fraction elemental maps of P, S, Cl, K, Ca, Fe and Zn of entire cryofrozen human fibroblasts were obtained. Despite the presence of diffracting microcrystals in the vitreous ice matrix and minor sample radiation damage effects, clusters of iron-rich hot-spots with similar mass fractions were found in the cytoplasm of both control and FRDA fibroblasts. Interestingly, no significant difference in the mean iron concentration was found in the cytoplasm of FRDA fibroblasts, but a significant decrease in zinc concentration. This finding might underscore metal dysregulation, beyond iron, in cells derived from FRDA patients. In conclusion, although currently having slightly increased limits of detection (LODs) compared to non-cryogenic mode, SR based nanoscopic XRF under cryogenic sample conditions largely obliterates the debate on chemical sample preservation and provides a unique tool for trace level elemental imaging in single cells close to their native state with a superior spatial resolution of 20 nm.

Luminescent thermometer based on Eu3+ /Tb3+ -organic-functionalized mesoporous silica.

In this work we investigate a mesoporous silica (MS) decorated with dipyridyl-pyridazine (dppz) ligands and further grafted with a mixture of Eu3+ /Tb3+ ions (28.45%:71.55%), which was investigated as a potential thermometer in the 10-360 K temperature range. The MS material was prepared employing a hetero Diels-Alder reaction: 3,6-di(2-pyridyl)-1,2,4,5-tetrazine was reacted with the double bonds of vinyl-silica (vSilica) followed by an oxidation procedure. We explore using the dppz-vSilica material to obtain visible emitting luminescent materials and for obtaining a luminescent thermometer when grafted with Eu3+ /Tb3+ ions. For the dppz-vSilica@Eu,Tb material absolute sensitivity Sa of 0.011 K-1 (210 K) and relative sensitivity Sr of 1.32 %K-1 (260 K) were calculated showing good sensing capability of the material. Upon temperature change from 10 K to 360 K the emission color of the material changed gradually from yellow to red.

Integrated Three-Dimensional Microanalysis Combining X-Ray Microtomography and X-Ray Fluorescence Methodologies.

A novel 3D elemental and morphological analysis approach is presented combining X-ray computed tomography (µCT), X-ray fluorescence (XRF) tomography, and confocal XRF analysis in a single laboratory instrument (Herakles). Each end station of Herakles (µCT, XRF-CT, and confocal XRF) represents the state-of-the-art of currently available laboratory techniques. The integration of these techniques enables linking the (quantitative) spatial distribution of chemical elements within the investigated materials to their three-dimensional (3D) internal morphology/structure down to 1-10 µm resolution level, which has not been achieved so-far using laboratory X-ray techniques. The concept of Herakles relies strongly on its high precision (around 100 nm) air-bearing motor system that connects the different end-stations, allowing combined measurements based on the above X-ray techniques while retaining the coordinate system. In-house developed control and analysis software further ensures a smooth integration of the techniques. Case studies on a Cu test pattern, a Daphnia magna model organism and a perlite biocatalyst support material demonstrate the attainable resolution, elemental sensitivity of the instrument, and the strength of combining these three complementary methodologies.

Grafting of a Eu3+-tfac complex on to a Tb3+-metal organic framework for use as a ratiometric thermometer.

Microrods of [Tb2(bpydc)3(H2O)3]·nDMF (TbMOF) were employed as a platform for grafting a ß-diketonate complex of Eu3+ for the purpose of obtaining ratiometric luminescence thermometer materials. A straightforward post-synthetic functionalization is employed to obtain the TbMOF@Eu_tfac (tfac = trifluoroacetylacetonate) compounds. The emission color of the TbMOF@Eu compounds can be slightly tuned by varying the percentage of the grafted ß-diketonate complex of Eu3+. Also, as shown, the thermometric properties of the material can be tuned by the percentage of grafted ß-diketonate complex of Eu3+. The TbMOF@3%Eu_tfac and TbMOF@7.3%Eu_tfac compounds were investigated in detail for their use as luminescent ratiometric thermometers. For the TbMOF@3%Eu_tfac compound an absolute sensitivity Sa of 0.069 K-1 (225 K) and relative sensitivity Sr of 2.59%K-1 (225 K) were obtained showing its good sensing capability. For the TbMOF@7.3%Eu_tfac compound a Sa of 0.012 K-1 (275 K) and relative sensitivity Sr of 1.33%K-1 (325 K) were obtained showing that the TbMOF@3%Eu_tfac compound is superior for temperature sensor applications. We also show that the emission color of the parent TbMOF material itself can be tuned by varying the excitation wavelength from 250-380 nm. It can be tuned from light-green to blue by simply changing the excitation wavelength.

Three-Dimensional Reconstruction of the Tissue-Specific Multielemental Distribution within Ceriodaphnia dubia via Multimodal Registration Using Laser Ablation ICP-Mass Spectrometry and X-ray Spectroscopic Techniques.

In this work, the three-dimensional elemental distribution profile within the freshwater crustacean Ceriodaphnia dubia was constructed at a spatial resolution down to 5 µm via a data fusion approach employing state-of-the-art laser ablation-inductively coupled plasma-time-of-flight mass spectrometry (LA-ICP-TOFMS) and laboratory-based absorption microcomputed tomography (µ-CT). C. dubia was exposed to elevated Cu, Ni, and Zn concentrations, chemically fixed, dehydrated, stained, and embedded, prior to µ-CT analysis. Subsequently, the sample was cut into 5 µm thin sections that were subjected to LA-ICP-TOFMS imaging. Multimodal image registration was performed to spatially align the 2D LA-ICP-TOFMS images relative to the corresponding slices of the 3D µ-CT reconstruction. Mass channels corresponding to the isotopes of a single element were merged to improve the signal-to-noise ratios within the elemental images. In order to aid the visual interpretation of the data, LA-ICP-TOFMS data were projected onto the µ-CT voxels representing tissue. Additionally, the image resolution and elemental sensitivity were compared to those obtained with synchrotron radiation based 3D confocal µ-X-ray fluorescence imaging upon a chemically fixed and air-dried C. dubia specimen.

Application toward Confocal Full-Field Microscopic X-ray Absorption Near Edge Structure Spectroscopy.

Using X-ray absorption near edge structure (XANES) spectroscopy, information on the local chemical structure and oxidation state of an element of interest can be acquired. Conventionally, this information can be obtained in a spatially resolved manner by scanning a sample through a focused X-ray beam. Recently, full-field methods have been developed to obtain direct 2D chemical state information by imaging a large sample area. These methods are usually in transmission mode, thus restricting the use to thin and transmitting samples. Here, a fluorescence method is displayed using an energy-dispersive pnCCD detector, the SLcam, characterized by measurement times far superior to what is generally applicable. Additionally, this method operates in confocal mode, thus providing direct 3D spatially resolved chemical state information from a selected subvolume of a sample, without the need of rotating a sample. The method is applied to two samples: a gold-supported magnesia catalyst (Au/MgO) and a natural diamond containing Fe-rich inclusions. Both samples provide XANES spectra that can be overlapped with reference XANES spectra, allowing this method to be used for fingerprinting and linear combination analysis of known XANES reference compounds.

Probing Intracellular Element Concentration Changes during Neutrophil Extracellular Trap Formation Using Synchrotron Radiation Based X-Ray Fluorescence.

High pressure frozen (HPF), cryo-substituted microtome sections of 2 µm thickness containing human neutrophils (white blood cells) were analyzed using synchrotron radiation based X-ray fluorescence (SR nano-XRF) at a spatial resolution of 50 nm. Besides neutrophils from a control culture, we also analyzed neutrophils stimulated for 1-2 h with phorbol myristate acetate (PMA), a substance inducing the formation of so-called Neutrophil Extracellular Traps (or NETs), a defense system again pathogens possibly involving proteins with metal chelating properties. In order to gain insight in metal transport during this process, precise local evaluation of elemental content was performed reaching limits of detection (LODs) of 1 ppb. Mean weight fractions within entire neutrophils, their nuclei and cytoplasms were determined for the three main elements P, S and Cl, but also for the 12 following trace elements: K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Se, Br, Sr and Pb. Statistical analysis, including linear regression provided objective analysis and a measure for concentration changes. The nearly linear Ca and Cl concentration changes in neutrophils could be explained by already known phenomena such as the induction of Ca channels and the uptake of Cl under activation of NET forming neutrophils. Linear concentration changes were also found for P, S, K, Mn, Fe, Co and Se. The observed linear concentration increase for Mn could be related to scavenging of this metal from the pathogen by means of the neutrophil protein calprotectin, whereas the concentration increase of Se may be related to its antioxidant function protecting neutrophils from the reactive oxygen species they produce against pathogens. We emphasize synchrotron radiation based nanoscopic X-ray fluorescence as an enabling analytical technique to study changing (trace) element concentrations throughout cellular processes, provided accurate sample preparation and data-analysis.

Nanoscopic tumor tissue distribution of platinum after intraperitoneal administration in a xenograft model of ovarian cancer.

There is increasing interest in the treatment of advanced stage ovarian cancer (OC) using intraperitoneal (IP) delivery of platinum (Pt)-based chemotherapy. The antitumor efficacy of IP chemotherapy is determined by efficient tumor tissue penetration. Although it is assumed that Pt penetration is limited to a few millimeters after IP delivery, little is known on the distribution of Pt in different tumor compartments at the ultrastructural level following IP administration. Here, using synchrotron radiation X-ray fluorescence spectrometry (SR-XRF) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), Pt distribution and penetration in OC peritoneal xenografts were determined at nanometer scale after IP chemoperfusion of cisplatin at 37-38°C or 40-41°C (hyperthermic). Using principal component analysis (PCA) the presence of phosphorus, manganese, calcium, zinc, iron, bromine, and sulfur was correlated with the distribution of Pt, while k-means analysis was used to quantify the amount of Pt in weight% in tumor stroma and in tumor cells. The results showed a heterogeneous distribution of Pt throughout the tumor, with an accumulation in the extracellular matrix. LA-ICP-MS mappings indicated significantly higher concentrations of Pt (P=0.0062) after hyperthermic chemoperfusion of cisplatin, while SR-XRF demonstrated a deeper tissue Pt penetration after hyperthermic treatment. Using PCA, it was showed that Pt co-localizes with bromine and sulfur. No differences were observed in Pt distribution regarding tumor cells and stroma, when comparing normo- vs. hyperthermic treatment. In conclusion, SR-XRF and LA-ICP-MS are suitable and highly sensitive techniques to analyze the penetration depth and distribution of Pt-based drugs after IP administration. To the best of our knowledge, this is the first experiment in which the distribution of Pt is analyzed at the cellular level after IP administration of cisplatin.

Assessment of Ovarian Cancer Tumors Treated with Intraperitoneal Cisplatin Therapy by Nanoscopic X-ray Fluorescence Imaging.

Ovarian cancer is amongst the most common types of cancer in women, with a relatively low overall cure rate of approximately 30%. This is therefore an important incentive to urge for further research in order to maximize the chances of survival for these patients. Intraperitoneal chemotherapy with Cisplatin is an effective treatement for ovarian cancer; however, many questions still remain concerning the ideal treatment protocol and tumor resistance towards the drug, which should be resolved for optimal application of this therapy. For the first time in-vivo grown tumors treated with both hyper- and normothermic intraperitoneal chemotherapy have been studied using nano-XRF spectroscopy to examine the platinum (Pt) distribution within the analyzed tissues. These measurements prove Pt resides predominantly outsides the cancer cells in the stroma of the tissue. These findings indicate the resistance mechanism of the cancer cells prevents Cisplatin from diffusing through their cell membranes. This is an important addition to the existing knowledge on the resistance mechanism providing insights which might help to overcome this effect. In our aim to find the optimal treatment protocol, no significant differences were found between the two examined procedures. A more extensive data set will be needed to draw definite conclusions.

Laboratory Scale X-ray Fluorescence Tomography: Instrument Characterization and Application in Earth and Environmental Science.

A new laboratory scale X-ray fluorescence (XRF) imaging instrument, based on an X-ray microfocus tube equipped with a monocapillary optic, has been developed to perform XRF computed tomography experiments with both higher spatial resolution (20 µm) and a better energy resolution (130 eV @Mn-K(α)) than has been achieved up-to-now. This instrument opens a new range of possible applications for XRF-CT. Next to the analytical characterization of the setup by using well-defined model/reference samples, demonstrating its capabilities for tomographic imaging, the XRF-CT microprobe has been used to image the interior of an ecotoxicological model organism, Americamysis bahia. This had been exposed to elevated metal (Cu and Ni) concentrations. The technique allowed the visualization of the accumulation sites of copper, clearly indicating the affected organs, i.e. either the gastric system or the hepatopancreas. As another illustrative application, the scanner has been employed to investigate goethite spherules from the Cretaceous-Paleogene boundary, revealing the internal elemental distribution of these valuable distal ejecta layer particles.

Nanoscopic X-ray fluorescence imaging of meteoritic particles and diamond inclusions.

The new ESRF ID16B-NA Nanoanalysis beamline has been applied for the first time for XRF imaging with a resolution level down to a few tens of nanometers on rare geological materials: meteoritic fragments from achondrite NWA 6693 and diamond inclusions. The instrument proved to be an extremely valuable tool for mapping samples containing submicrometer heterogeneities. It was discovered that the track of bubblelike inclusions in NWA 6693 consists mainly of Cr-rich phases. Some inclusions containing Ni and Ca were also detected. In diamond SL05, originating from the Juina region in Brazil, multiple inclusions were analyzed with dimensions smaller than 1 µm. Raman spectrometry measurements indicated the presence of a ringwoodite inclusion in this diamond; the detection of several iron-rich inclusions justifies further investigation of this material.

Full-field fluorescence mode micro-XANES imaging using a unique energy dispersive CCD detector.

X-ray absorption near-edge structure (XANES) spectroscopy is a well-known nondestructive technique that allows for chemical state and local structure determination. Spatially resolved oxidation state imaging is possible performing full-field transmission mode XANES experiments, providing chemical state information on the illuminated sample area, but these experiments are limited to thin, concentrated samples. Here we present the use of a unique energy dispersive (ED) pnCCD detector, the SLcam, for full-field fluorescence mode XANES experiments, thereby significantly relaxing the constraints on sample thickness. Using this new detection methodology, spatially resolved chemical state information on millimeter-sized sample areas can be obtained with microscopic resolution in moderate measuring times (less than 15 h), obtaining a XANES profile for each of nearly 70,000 points in a single measurement without the need of scanning the sample through the beam. Besides a description of the use of this detector for micro-XANES applications, we also present the proof of concept for fluorescence mode micro-XANES using a Fe(0)/Fe2O3 model sample and a Nitisol soil sample, which was measured to obtain iron chemical state distribution information.