Hard X-ray nanoprobe investigations of the subtissue metal distributions within Daphnia magna
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RESEARCH PAPER
Hard X-ray nanoprobe investigations of the subtissue metal distributions within Daphnia magna B. De Samber & K. A. C. De Schamphelaere & C. R. Janssen & B. Vekemans & R. De Rycke & G. Martinez-Criado & R. Tucoulou & P. Cloetens & L. Vincze
Received: 7 December 2012 / Revised: 19 April 2013 / Accepted: 23 April 2013 / Published online: 17 May 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract The unique potential of nanoscale elemental imaging of major/minor and trace-level elemental distributions within thin biological tissue sections of the ecotoxicological model organism Daphnia magna is demonstrated by synchrotron radiation nano-X-ray fluorescence (nano-XRF). The applied highly specialized sample preparation method, coupled with the high spatial resolution (∼180 nm) and high X-ray photon flux (6×1011 photons/s) available at the European Synchrotron Radiation Facility (ESRF) ID22NI beamline proved to be critical for the high-quality visualization of (trace-)metal distributions on the submicron level within the target structures of interest. These include the branchial sacs on the thoracic appendages (epipodites) of D. magna, which are osmoregulatory regions where ion exchange occurs. For the main element of interest (Zn), detection limits of 0.7 ppm (3 ag) was reached in fast-scanning mode using an acquisition time of B. De Samber (*) : B. Vekemans : L. Vincze Department of Analytical Chemistry, Ghent University, Krijgslaan 281 (S12), 9000 Ghent, Belgium e-mail: [email protected] K. A. C. De Schamphelaere : C. R. Janssen Laboratory of Environmental Toxicology and Applied Ecology, Department of Applied Ecology and Environmental Biology, Ghent University, Plateaustraat 22, 9000 Ghent, Belgium R. De Rycke Department of Molecular Biomedical Research, Flanders Institute for Biotechnology (VIB), 9000 Ghent, Belgium R. De Rycke Department of Biomedical Molecular Biology, Ghent University, 9052 Ghent, Belgium G. Martinez-Criado : R. Tucoulou : P. Cloetens European Synchrotron Radiation Facility (ESRF), 6 Rue Jules Horowitz, 38043 Grenoble, France
0.3 s/pixel. As demonstrated, synchrotron radiation nano-XRF revealed the elemental distributions of Ca, Fe, and Zn within this osmoregulatory region on the submicron scale, aiding the exploration of possible detoxification mechanisms of Zn within D. magna at the subtissue level. Keywords Nano-XRF . Ecotoxicology . Daphnia magna . Metallomics . OsO4 staining
Introduction The freshwater crustacean Daphnia magna is an important and frequently used model organism to investigate toxicity, uptake, elimination, and detoxification processes associated with the exposure to transition metals (e.g., Cu, Zn, and Ni) [1, 2]. Since biological effects due to metals are initiated by metal bioaccumulation, the fundamental processes underlying bioaccumulation will lead to an improved capacity to evaluate the impact of metals on aquatic organisms [3]. Aquatic biota regulate their internal concentrations of essential metals through active regulation, storage/detoxificat
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