As metal oxide nanoparticles gain use in a wide range of technology sectors it is important to understand the biological and environmental impacts of these materials. There are three leading theories about the mechanism of toxicity specific to nanoparticles: (1) reactive oxygen species generation at a reactive nanoparticle surface, (2) the leaching of toxic ions from the nanoparticle core, and (3) cascades of detrimental redox reactions resulting from the inherent electronic structure of the core material. Our understanding of how specific structural properties influence nanoparticle toxicity is clouded by the difficulty in synthesizing uniform metal oxide nanoparticles with tunable structural features. Further, studies investigating the same core material made through different synthetic routes often yield contradictory toxicity results. We can eliminate much of the structural variation responsible for these contradictory results by exploiting recent advances in metal oxide nanoparticle synthesis and surface chemistry modification To this end, we have synthesized a series of six metal oxide nanoparticles to study the influence of electronic structure, ion leaching, and surface passivation on nanoparticle induced toxicity. Three different metal oxide core materials were chosen to investigate the influence of core composition: α-Fe2O3, In2O3 and CoO. The surface chemistry of each core material was modified, from the same batch of starting nanoparticles, to produce an un-passivated and passivated core. The embryonic zebrafish toxicity assay revealed a clear trend in toxicity in vivo: the un-passivated nanoparticles induced mortality within 24 hours while the passivated nanoparticles did not, regardless of core composition or the toxicity of leached ions. These results suggest that surface passivation is a key factor that dictates biocompatibility, even for core materials that are considered benign materials, and that highly reactive nanoparticle core materials may be rendered biocompatible by passivating the surface with deliberately added ligands.

Surface passivation, not core composition, drives metal oxide nanoparticle biocompatibility

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.