Abstract:

 The number of nanoparticle-containing products has increased rapidly over the last decade and nanoparticles can be released into the environment either intentionally or unintentionally during or after production and use. Understanding of their behavior and effects is necessary for estimating risks to the environment and human health. Our nano team studies toxicity, bioavailability as well as transcriptomic, genomic and epigenetic effects of metal and metal oxide manufactured nanoparticles (MNP) in their pristine (as synthesized) and environmentally modified (aged) forms.  For example, Ag-MNPs after entering wastewater streams are rapidly transformed to Ag₂S.  Here we present results on bioavailability and toxicogenomic responses of a model organism, a nematode Caenorhabditis elegans to pristine Ag-MNPs, sulfidized (sAg-MNPs), and AgNO₃. The toxicity and transcriptomic effects of pristine Ag-MNPs involve uptake and bioaccumulation of Ag and is explained by both dissolution and release of Ag ions as well as by particle-specific effects. In contrast, the toxicity of the transformed sAg-MNPs is largely independent of free ion release and Ag bioaccumulation. Cuticle damage is likely to be one of the primary toxicity mechanisms for the sAg-MNPs.

We have been also investigating mutigenerational effects of MNPs and our recent multigenerational study has shown enhanced C. elegans sensitivity for reproductive toxicity as early as second generation for AgNO₃and Ag-MNPs, but not sAg-MNPs. This suggested that Ag-MNPs may cause mutations or epi-mutations. Using a next generation sequencing approach and changes in levels of DNA (adenine) methylation we are evaluating germ-line mutations and epigenetic modifications that might be induced and passed to subsequent generations after continuous exposure of C. elegans to Ag-MNPs.