Synchrotron X-ray 2D and 3D elemental imaging of CdSe/ZnS quantum dot nanoparticles in Daphnia magna
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The potential toxicity of nanoparticles to aquatic organisms is of interest given that increased commercialization will inevitably lead to some instances of inadvertent environmental exposures. Cadmium selenide quantum dots (QDs) capped with zinc sulfide are used in the semiconductor industry and in cellular imaging. Their small size (<10 nm) suggests that they may be readily assimilated by exposed organisms. We exposed Daphnia magna to both red and green QDs and used synchrotron X-ray fluorescence to study the distribution of Zn and Se in the organism over a time period of 36 h. The QDs appeared to be confined to the gut, and there was no evidence of further assimilation into the organism. Zinc and Se fluorescence signals were highly correlated, suggesting that the QDs had not dissolved to any extent. There was no apparent difference between red or green QDs, i.e., there was no effect of QD size. 3D tomography confirmed that the QDs were exclusively in the gut area of the organism. It is possible that the QDs aggregated and were therefore too large to cross the gut wall.
KeywordsNanoparticles Quantum dots Synchrotron XRF Elemental imaging Tomography
This work was supported by US EPA RD-83332401-0 to BJ and JR. The work was performed at Beamlines X27A and X26A, National Synchrotron Light Source (NSLS), Brookhaven National Laboratory. Beamline X26A is supported by the Department of Energy (DOE)-Geosciences (DE-FG02-92ER14244 to The University of Chicago-CARS). Use of the NSLS and Beamline X27A was supported by DOE under contract no. DE-AC02-98CH10886.
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