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Differential gene expression in Daphnia magna suggests distinct modes of action and bioavailability for ZnO nanoparticles and Zn ions
Citation:
POYNTON, H., J. M. LAZORCHAK, C. IMPELLITTERI, MARK E. SMITH, K. R. ROGERS, M. Patra, K. A. Hammer, JOEL J. ALLEN, AND C. D. Vulpe. Differential gene expression in Daphnia magna suggests distinct modes of action and bioavailability for ZnO nanoparticles and Zn ions. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 45(2):762-768, (2011).
Impact/Purpose:
The aim of this study is to use gene expression analysis to determine if the toxicity of ZnO NPs to the aquatic crustacean, D. magna, is due to dissolution of NPs and identify biomarkers of nanoparticle exposure that may be developed to detect NP exposure in the environment, distinguishing between NP and ion exposure.
Description:
Zinc oxide nanoparticles (ZnO NPs) are being rapidly developed for use in consumer products, wastewater treatment and chemotherapy, providing several possible routes for ZnO NP exposure to humans and aquatic organisms. Recent studies have shown that ZnO NPs undergo rapid dissolution to Zn+2, but the relative contribution of Zn+2 to ZnO NP bioavailability and toxicity is not clear. We show that a fraction of the ZnO NPs in suspension dissolves and this fraction cannot account for the toxicity of the ZnO NP suspensions to Daphnia magna. Gene expression profiling of D. magna exposed to ZnO NPs or ZnSO4 at equitoxic concentrations demonstrated distinct mechanisms of toxicity. ZnO NPs effected expression of genes involved in cytoskeletal transport, cellular respiration and reproduction. A specific pattern of differential expression of three biomarker genes including a multi-cystatin, ferritin and a Clq containing gene were confirmed for ZnO NP exposure and provide a suite of biomarkers for identifying environmental exposure to ZnO NP and differentiating between NP and ionic exposure.