Physicochemical Characteristics of Polymer-Coated Metal-Oxide Nanoparticles and their Toxicological Effects on Zebrafish (Danio rerio) Development

Coated nanoparticles (NPs) will end up in the environment due to their proposed use in agricultural applications and may potentially cause toxic effects due to their unique properties. To determine the effects of coated NPs on zebrafish (Danio rerio) development, we tested aqueous poly(acrylic acid) (PAA)-coated metal-oxide NPs including TiO2, ZnO, Fe2O3, and CeO2, as well as the polymer coating alone (nanocapsule). Zebrafish embryos were exposed to NPs over a 72 h period at 1, 10, 50, 100, 200, 400, 800, 1200, 1600, and 2000 mg/L to measure various end points. We also ran free metal controls. Time-dependent changes in physicochemical properties of NPs were characterized using dynamic light scattering. Dissolution experiments over 72 h showed minimal free metals were present in stock suspensions and released from the NPs. Interestingly, nanocapsules (≥800 mg/L) cause inhibition of hatch, and we suggest that a low pH environment may explain this effect. This study has also demonstrated that CeO2 NPs and nanocapsules containing Nile red are able to traverse the chorion. Overall, our findings indicate that each NP type is stable and neither the NP or encapsulating PAA coating causes apparent toxicity to developing zebrafish.