Thibaut Van Acker

Imaging the 3D trace metal and metalloid distribution in mature wheat and rye grains via laser ablation-ICP-mass spectrometry and micro-X-ray fluorescence spectrometry

Toxic trace metals and metalloids in human nutrient sources pose a severe health risk, and the processes governing metal accumulation should hence be well understood. In this work, the spatial distribution of toxic trace metals/metalloids and micronutrients (Cr, Mn, Ni, Cu, Zn, As, Cd, Hg and Pb) in mature wheat (Triticum aestivum L.) and rye (Secale cereale L.) grains at typical exposure levels was visualized and quantified via laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) by serial sectioning. The bulk concentrations of these elements were also determined by pneumatic nebulisation-ICP-MS. Furthermore, longitudinal sections were scanned using m-X-ray fluorescence spectrometry to confirm the major element distribution. Serial sectioning in this study was realized via a polishing strategy. Although the methodology is time-consuming and laborious, it enables to access 3D information for samples which cannot be sectioned using a microtome on a depth scale that would otherwise be inaccessible by a laser probe. In the elemental images, strong local enrichment patterns for Mn and Zn are apparent in the aleurone layer/seed coat, vascular tissue of the crease, and embryonic tissue, whereas Cr, As, Cd and Pb have been mainly accumulated in the grain endosperm as a result of different transport and storage dynamics.

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.

Identification of platinum nanoparticles in road dust leachate by single particle inductively coupled plasma-mass spectrometry

Elevated platinum (Pt) concentrations are found in road dust as a result of emissions from catalytic converters in vehicles. This study investigates the occurrence of Pt in road dust collected in Ghent (Belgium) and Gothenburg (Sweden). Total Pt contents, determined by tandem ICP-mass spectrometry (ICP-MS/MS), were in the range of 5 to 79ngg-1, comparable to the Pt content in road dust of other medium-sized cities. Further sample characterization was performed by single particle (sp) ICP-MS following an ultrasonic extraction procedure using stormwater runoff for leaching. The method was found to be suitable for the characterization of Pt nanoparticles in road dust leachates. The extraction was optimized using road dust reference material BCR-723, for which an extraction efficiency of 2.7% was obtained by applying 144kJ of ultrasonic energy. Using this method, between 0.2% and 18% of the Pt present was extracted from road dust samples. spICP-MS analysis revealed that Pt in the leachate is entirely present as nanoparticles of sizes between 9 and 21nm. Although representing only a minor fraction of the total content in road dust, the nanoparticulate Pt leachate is most susceptible to biological uptake and hence most relevant in terms of bioavailability.

Laser ablation-inductively coupled plasma-mass spectrometry for quantitative mapping of the copper distribution in liver tissue sections from mice with liver disease induced by common bile duct ligation

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was deployed for quantitative mapping of the Cu distribution in cryo-sections of liver tissue from mice with cholestatic liver disease induced via common bile duct ligation (CBDL). Cu distribution maps of the liver sections were obtained from the CBDL-operated mice sacrificed at different time points (2, 4 and 6 weeks) after the surgical intervention and compared with those of the corresponding control (sham-operated) mice. Cu quantification was accomplished versus matrix-matched thin sections of spiked liver tissue homogenates and versus spiked gelatin droplet standards. No statistical differences were obtained between the results using the two calibration approaches and thus, both were considered suitable for quantitative Cu bioimaging of liver cryo-sections. On the basis of practical considerations, i.e. simplicity, low cost and availability of the material, spiked gelatin droplet standards are the preferred choice for quantitative determination of the Cu distribution in liver tissue cryo-sections. An inhomogeneous hepatic Cu distribution was observed in the CBDL mice, in contrast to the homogeneous hepatic Cu distribution established for the sham-operated mice. The Cu levels increased with the progression of the disease and a strong accumulation was observed in some necrotic areas. High-resolution LA-ICP-MS bioimaging, using a circular spot size of 2 μm, was suitable for the visualization of the Cu distribution in liver tissue on a (sub-)cellular level. In addition to the quantitative Cu mapping, the spatial distribution of Zn was also monitored in the liver cryo-sections of the control and the 2, 4 and 6 week CBDL mice, but in all cases, Zn was homogeneously distributed across the tissue.

Fast High-Resolution Laser Ablation-Inductively Coupled Plasma Mass Spectrometry Imaging of the Distribution of Platinum-Based Anticancer Compounds in Multicellular Tumor Spheroids

Multicellular tumor spheroid models serve as an important three-dimensional in vitro cell model system as they mimic the complex tumor microenvironment and thus have contributed to valuable assays in drug discovery studies. In this study, we present a state-of-the-art laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) setup for high spatial resolution elemental imaging of multicellular tumor spheroids and an approach to account for variations in cell density. A low dispersion LA-ICPMS setup was employed, providing accelerated throughput and high sensitivity and permitting a lateral image resolution down to ∼2.5 μm for phosphorus and platinum in HCT116 colon cancer spheroids upon treatment with the clinically used anticancer drug oxaliplatin. Phosphorus was introduced as scalar to compensate for differences in cell density and tissue thickness and the Pt/P ratios together with the high resolution adopted in our approach allows the differentiation of platinum accumulation within each part of the morphology of the tumor spheroids (layers of proliferating, quiescent, and necrotic cells).

High-speed sub-micrometer imaging of sub-cellular structures in single cells using ARIS

© 2017 Teledyne CETAC Technologies TECHNICAL NOTE: ANALYTE G2-003 High-speed sub-micrometer imaging of sub-cellular structures in single cells using ARIS Thibaut Van Acker1, Stijn J.M. Van Malderen1, Tessa Buckle2, Frank Vanhaecke1 1Department of Analytical Chemistry, Ghent University, Campus Sterre, Krijgslaan 281 S12, 9000 Ghent, Belgium 2Interventional Molecular Imaging Laboratory, Department of Radiology, Leiden University Medical Center, Albinusdreef 2, 2300 RC Leiden, the Netherlands