Elements In Thin Sections Research Articles

Quantitative Imaging of Silver Nanoparticles and Essential Elements in Thin Sections of Fibroblast Multicellular Spheroids by High Resolution Laser Ablation Inductively Coupled Plasma Time-of-Flight Mass Spectrometry.

We applied high resolution laser ablation inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOF-MS) with cellular spatial resolution for bioimaging of nanoparticles uptaken by fibroblast multicellular spheroids (MCS). This was used to quantitatively investigate interactions of silver nanoparticles (Ag NPs) and the distributions of intrinsic minerals and biologically relevant elements within thin sections of a fibroblast MCS as a three-dimensional in vitro tissue model. We designed matrix-matched calibration standards for this purpose and printed them using a noncontact piezo-driven array spotter with a Ag NP suspension and multielement standards. The limits of detection for Ag, Mg, P, K, Mn, Fe, Co, Cu, and Zn were at the femtogram (10-15 g) level, which is sufficient to investigate intrinsic minerals in thin MCS sections (20 μm thick). After incubation for 48 h, Ag NPs were enriched in the outer rim of the MCS but not detected in the core. The localization of Ag NPs was inhomogeneous in the outer rim, and they were colocalized with a single-cell-like structure visualized by Fe distribution (pixel size of elemental images: 5 × 0.5 μm). The quantitative value for the total mass of Ag NPs in a thin section by the present method agreed with that obtained by ICP-sector field (SF)-MS with a liquid mode after acid digestion.

Laser ablation inductively coupled plasma mass spectrometry in quantitative analysis and imaging of plant's thin sections

Laser ablation coupled with ICP-MS was used for quantitative imaging of the distribution of toxic and essential elements in thin sections of Pisum sativum L. (pea) tissues. A novel approach was applied for quantification of metal accumulation: instead of carbon we used sulfur isotope as an internal standard. Laser ablation was performed on in vivo cross-sections through areas of roots and stems, to examine peas’ ability to uptake and transport metals to the above-ground parts of the plant. Ion intensities of 111Cd, 65Cu, 208Pb and 66Zn were measured in plant tissue together with 34S serving as an internal standard. Calibration curve was obtained using standard addition method NIST SRM 1515 Apple Leaves spiked with standard. Application of sulfur isotope as an internal standard was successful: analytical results obtained by LA-ICP-MS and ICP-MS analysis were comparable in terms of accuracy, precision and limits of detection.

Quantitative images of metals in plant tissues measured by laser ablation inductively coupled plasma mass spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used for quantitative imaging of toxic and essential elements in thin sections (thickness of 30 or 40 μm) of tobacco plant tissues. Two-dimensional images of Mg, Fe, Mn, Zn, Cu, Cd, Rh, Pt and Pb in leaves, shoots and roots of tobacco were produced. Sections of the plant tissues (fixed onto glass slides) were scanned by a focused beam of a Nd:YAG laser in a laser ablation chamber. The ablated material was transported with argon as carrier gas to the ICP ion source at a quadrupole ICP-MS instrument. Ion intensities of the investigated elements were measured together with 13C +, 33S + and 34S + within the entire plant tissue section. Matrix matching standards (prepared using powder of dried tobacco leaves) were used to constitute calibration curves, whereas the regression coefficient of the attained calibration curves was typically 0.99. The variability of LA-ICP-MS process, sample heterogeneity and water content in the sample were corrected by using 13C + as internal standard. Quantitative imaging of the selected elements revealed their inhomogeneous distribution in leaves, shoots and roots.

Hard X-ray microprobe studies of chromium(VI)-treated V79 Chinese hamster lung cells: intracellular mapping of the biotransformation products of a chromium carcinogen

The uptake of carcinogenic and mutagenic Cr compounds and the intracellular distribution of their biotransformation products in V79 Chinese hamster lung cells were studied by synchrotron-radiation-induced X-ray emission (SRIXE). SRIXE analysis was performed on whole cells that had been treated with either Cr(III) or Cr(V) 1,10-phenanthroline complexes, or Cr(VI). The high spatial resolution (0.3 microm) and elemental sensitivity (~10(-15) g Cr/cell) of the technique provided detailed maps of Cr and other cellular elements in thin sections prepared from Cr(VI)-treated cells. The Cr carcinogen concentrated in P-rich regions corresponding to the nucleus, as well as other areas of the cell that are likely to correspond to organelles. This is the first study that has enabled the determination of the localization of the biotransformation products of Cr(VI) carcinogens in a target lung cell.

Rapid Contrasting of Extracellular Elements in Thin Sections

Standard methods for contrasting ultrathin sections generally have their greatest effect on cells and cellular components, whereas extracellular elements remain relatively electron-lucent. Occasionally, some extracellular elements even fail completely to react with the staining solutions. We describe a method for rendering a uniformly high contrast to extracellular tissue components. This consists of a brief prestaining of grids with diluted tannic acid in distilled water. Simple, rapid, and versatile, this procedure can be routinely applied to all tissue samples examined by electron microscopy. As an additional advantage, the method greatly enhances the electron density of intracellular glycogen. Higher concentrations of tannic acid give increased electron density, especially to elastin, and can therefore be used as an elastin stain.

Quantitative analysis of trace and major elements in thin sections of soils with the secondary ion microscope (Cameca)

A series of experiments have been performed for a number of years to obtain quantitative microchemical analysis by secondary ion microscopy of materials in thin sections of soils. The first successful quantification was obtained from an area with a diameter of 300 μm in bauxite and done with an IMS 300 at Philips Research Laboratories. Such an area, however, is frequently too large for most soil samples which are extremely heterogeneous even on a microscale. A second generation IMS 3F was tested for soils at the Cameca factory in Paris. This instrument allows the quantification of trace and major elements of soil constituents in a spot with 1.5 μm diameter, using a computer program developed by Philips Research Laboratories. Calcite and clay from a Petrocalcic Xerochrept were used for this test. Ion spectra, ion images and linear traverses were made giving information on the nature and distribution of both major and trace elements. The possibility of investigating a larger number of chemical elements simultaneously in linear traverses is of considerable help in the study of thin sections. Various submicroscopic and other techniques are discussed to give some insight into the position of ion microscopy amongst these.

Light and heavy element detection in thin sections of soils with the ion microprobe mass analyzer (IMMA).

Previous research with the scanning electron microscope (SEM)-energy dispersive X-ray analyzer (EDXRA) and the electron microprobe analyzer (EMA), showed that the detection of light elements in thin sections of soils was problematic or even impossible. Consequently initial experiments were performed with the ion microprobe mass analyzer (IMMA). These preliminary investigations were carried out on a piece of root material in soil (containing both light and heavy elements) which has a 'clayey' appearance and is known as a clayified root (Parfenova et al., 1964). The presence of heavier elements in this sample was investigated by SEM-EDXRA prior to IMMA analysis. The results with the ion microprobe mass analyzer showed that all chemical elements could be analyzed in the plant fragment. Also much higher elemental detection sensitivities were found with IMMA as compared to SEM-EDXRA and EMA. This even allowed ion imaging of trace elements. High-quality ion images of both light and heavy elements could be obtained in much shorter exposure times than with SEM-EDXRA and EMA techniques. Furthermore by analysis of fragmentation ('fingerprint') spectra additional information was obtained with respect to the chemical binding of the analyzed elements. Due to these preliminary results IMMA offers full possibilities for microchemical analysis in situ of all important elements in soil specimens. This technique considerably increases possibilities in soil micromorphology. (Abstract retrieved from CAB Abstracts by CABI’s permission)

The mechanism of the fixation of tissue components by osmium tetroxide via hydrogen bonding

Considerable electron density, observable in membranous elements in thin sections of buffered OsO4-fixed tissue with electron microscopy, was removed by the action of K4Fe(CN)6 in acetic acid. This reagent reacted only with Os(VIII) and not with lower oxidation states of osmium to give an insoluble crystalline precipitate, K2FeOs(CN)6. Supporting this finding was the fact that the osmate esters, Os(VI), originally synthesized by Criegee (8, 9), were unreactive with acetic ferrocyanide. Acetic acid alone decreased membrane density of fixed sections by simple protonation but did not remove osmium from osmate esters. Further, fresh tissue incubated in a saturated urea solution, then fixed in buffered OsO4 not only failed to blacken, as routinely observed after OsO4 fixation, but also tissue structure was poorly preserved and membranous structures showed less electron density. Tissue fixed in a 1:1 solution of urea and OsO4 also demonstrated competition between the two compounds for binding sites in membranes. Thus, osmium in the Os(VIII) state appears responsible for some, if not much, of the membrane density, and is probably hydrogen bound in its native state as OsO4, to protein and to aliphatic side chains of lipid in membranes. Theoretical calculations pertaining to molecular interactions of OsO4 urea, and model proteins and lipids indicate that the above mechanistic hypothesis of the interaction of OsO4 with tissue components is favored over the mechanism of osmate ester formation with the double bonds in lipids as has been believed to date.