TiO2 nanoparticles reduce the effects of ZnO nanoparticles and Zn ions on zebrafish embryos (Danio rerio)

- The fate of ZnO NPs and TiO2NPs was assessed.
- Interactive effect of two NPs on fate of particulate and shedding ions was assessed.
- TiO2 NPs reduce the hatching impacts of ZnO NPs and Zn ions on zebrafish embryos.
- Relative contribution of ions and particle form of ZnO NPs to toxicity was assessed.
- The study has profound implications for manufacturing of safer-by-design products.

We investigated the toxicity of a mixture of stick-shaped ZnO nanoparticles (NPs) and spherical-shaped TiO2 NPs to zebrafish embryos (Danio rerio). The EC50 value of hatching inhibition of embryos exposed to suspensions of ZnO NPs was 1.3 mg/L. Upon addition of TiO2 NPs, the EC50 value increased by up to a maximum of a factor of 6.3. A similar reduction of toxicity was found for mortality of embryos, as the LC50 values were reduced significantly (p < 0.05) with the addition of TiO2 NPs at higher concentrations. A Zn(NO3)2 solution was used as a positive reference to assess the toxicity of Zn2 +. The toxicity of Zn2 + was reduced when TiO2 NPs were added, as compared to the effects found when embryos were exposed to Zn(NO3)2 solutions without TiO2 NPs. The contribution to toxicity of the particulate form of ZnO NPs was found to dominate the contribution of the released ions from ZnO NPs when explaining the toxicity of the suspensions of ZnO NPs in the absence and presence of TiO2 NPs to zebrafish embryos.

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