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Original Article

Silver nanoparticle-specific mitotoxicity in Daphnia magna

, , , , , , , , & show all
Pages 833-842 | Received 15 Apr 2013, Accepted 31 Jul 2013, Published online: 02 Sep 2013
 

Abstract

Silver nanoparticles (Ag NPs) are gaining popularity as bactericidal agents in commercial products; however, the mechanisms of toxicity (MOT) of Ag NPs to other organisms are not fully understood. It is the goal of this research to determine differences in MOT induced by ionic Ag+ and Ag NPs in Daphnia magna, by incorporating a battery of traditional and novel methods. Daphnia embryos were exposed to sublethal concentrations of AgNO3 and Ag NPs (130–650 ng/L), with uptake of the latter confirmed by confocal reflectance microscopy. Mitochondrial function was non-invasively monitored by measuring proton flux using self-referencing microsensors. Proton flux measurements revealed that while both forms of silver significantly affected proton efflux, the change induced by Ag NPs was greater than that of Ag+. This could be correlated with the effects of Ag NPs on mitochondrial dysfunction, as determined by confocal fluorescence microscopy and JC-1, an indicator of mitochondrial permeability. However, Ag+ was more efficient than Ag NPs at displacing Na+ within embryonic Daphnia, based on inductively coupled plasma-mass spectroscopy (ICP-MS) analysis. The abnormalities in mitochondrial activity for Ag NP-exposed organisms suggest a nanoparticle-specific MOT, distinct from that induced by Ag ions. We propose that the MOT of each form of silver are complementary, and can act in synergy to produce a greater toxic response overall.

Acknowledgments

This work was supported by the National Science Foundation (CBET-0854036). The authors would also like to acknowledge Michel Schweinsberg for digital image generation, Karl Wood at the Purdue Campus-Wide Mass Spectrometry Center for ICP-MS analysis and Aaron Taylor at the Bindley Bioscience Imaging Facility.

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