A combination of synchrotron and laboratory X-ray techniques for studying tissue-specific trace level metal distributions in Daphnia magna

Abstract

In the field of environmental toxicology, the study on the effects of the presence of transition metals such as Cu, Ni and Zn on the health of pelagic and benthic invertebrates is an important research topic. Fast dynamic 2D micro-XRF scanning and dynamic XRF micro-CT experiments on D. magna, a frequently used ecotoxicological model organism, allow the quantitative investigation of the accumulation of metals within specific organs with microscopic resolution. K-means clustering allows comparison of the concentrations of the elements of interest between different tissues/organs. Principal component analysis allows most of the significant statistical variations in these large and complex multivariate data sets to be explained. Also, by combining SR-XRF and absorption CT data sets using appropriate software packages, it becomes possible to unravel the tissue-specific 2D/3D distribution of metals in-situ within delicate organic samples on the 3-15 mu m resolution level in an essentially non-destructive manner

Element-to-tissue correlation in biological samples determined by three-dimensional X-ray imaging methods

“…Next to mechanical rigidity, this also implies that there should be no translocation of elements on a scale comparable with the resolution used during the micro-XRF scan. Already in our previous work 3, 4 we adapted a method by Tollrian et al, 12 who used HMDS (1,1,1,3,3,3-hexamethyldisilazane) as a drying agent in a successful preparation method for scanning electron microscopy (SEM) investigations of daphnids.…”

“…In our previous work, 3,4 we illustrated the potential of this technique when investigating Daphnia magna, a frequently used ecotoxicological model organism. Fast dynamic micro-XRF (2D) scanning and XRF micro-CT experiments on these organisms allowed the semi-quantitative investigation of the accumulation of metals within specific organs with microscopic resolution.…”

Spatially resolved 3D micro-XANES by a confocal detection scheme

“…Especially in biological and ecotoxicological systems confocal m-XAS can give useful complementary information. As a specific example, element-to-tissue correlation in Daphnia magna has been demonstrated with m-XRF and confocal m-XRF, [5][6]19 confocal m-XAS can add (intra-)tissue-specific metal speciation knowledge to this elemental information.…”

Scaling down the bioimaging of metals by laser microdissection inductively coupled plasma mass spectrometry (LMD-ICP-MS)

“…Element-specific imaging techniques like EFTEM (energyfiltering transmission electron microscopy) [7], scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX) [8], micro-XRF (X-ray fluorescence analysis) [9] or SIMS (secondary ion mass spectrometry) [10][11][12], cannot be applied to a series of open questions from the medicine, whereas synchrotron radiation XRF (SXRF) [13,14] and proton-induced X-ray emission (PIXE) [1] have extremely restricted availability. Several of these element analytical techniques provide a low dynamical range and encounter difficulties in quantifying analytical data.…”