Investigating the Mechanisms of Silver Nanoparticle Toxicity in Daphnia magna: A Multi-Omics Approach

Silver nanoparticles (AgNPs), one of the most common nanomaterials in use today, have been shown to enter the aquatic environment from use of commercially obtained products. Although acute toxicity has been shown in vitro and in vivo, there is still a great deal of uncertainty surrounding the molecular mechanism of AgNP-induced toxicity. Much of the current literature centres on the question of whether toxicity is induced by the AgNPs themselves or by ionic silver released from the nanoparticle surface. Here, I present research investigating AgNP toxicity to Daphnia magna, a keystone species of freshwater ecosystems the world over, using a multi-omics platform of transcriptomics and metabolomics techniques. Initially, the AgNPs were fully characterised and the exposure conditions optimised to accurately assess the impact of AgNP exposure to D. magna. This allowed for the design of sub-lethal AgNP exposures that had been fully controlled for the fraction of dissolved silver ions. Secondly, using this multi-omics platform, the role of Ag+ ions in AgNP toxicity to D. magna was determined. Finally a metabolic pathway perturbed by AgNP exposure was identified, as well as two constituent metabolites of key importance. Overall, this research advances the mechanistic understanding of AgNP toxicity to aquatic organisms, and further highlights the need for greater consideration of the nanoscale in regulative legislature.