Distinguishing nanomaterial and metal ion contributions to nanotoxicity: Zinc oxide nanoparticles and silver nanowires
Thursday, October 11, 2012
Benjamin Gilbert, Ph.D.
Staff Scientist, Lawrence Berkeley National Lab
Geochemistry Department, Nanogeoscience Center
Abstract: The growth of technological and industrial applications of engineered nanomaterials is leading to increased risk of their release into the environment. Many nanomaterials are unstable with respect to physical processes or chemical reactions that affect their mobility, bioavailability and toxicity. In particular, certain reactive nanomaterials contain toxic elements that can be released through dissolution. As a consequence, a major challenge is to identify the bioavailable forms of such nanomaterials, and the species responsible for toxicity. I will describe recent studies of the aqueous chemistry and toxicity of two nanomaterials: zinc oxide (ZnO) nanoparticles, used in sunscreen, and silver (Ag) nanowires, used as sensors and in flexible electronic materials. We studied the toxicity of ZnO nanoparticles to cultured cells, using optical microscopy and X-ray spectromicroscopy to support a model for ZnO nanoparticle uptake followed by intracellular dissolution. We studied the toxicity of Ag nanowires to Daphnia magna finding that oxidative dissolution in the growth medium was a poor predictor for toxicity. Imaging evidence for the internalization of the nanowires and gene expression studies indicated a role for internal dissolution.