The biological toxicities of two crystalline phases and differential sizes of TiO2 nanoparticles during zebrafish embryogenesis development

In this study, we investigated the biological toxicities of two crystalline phases and differential sizes of TiO2 nanoparticles (anatase; 7-8 nm, 12-14 nm, and 17-23 nm, rutile; 80-100 nm, 150-200 nm, and 500 nm) using the zebrafish in an aquatic ecosystem. The zebrafish morphants that survived exposure to the TiO2 nanoparticles exhibited incomplete notochord formation, with epidermal malformations observed in the larvae exposed to the anatase crystal type of TiO2 nanoparticle (12-14 nm). In particular, there was more apoptosis after exposure to specific particle sizes (12-14 nm) than there was with the larger particle size (17-23 nm) of the anatase crystal type of TiO2 nanoparticles. In addition, the group exposed to the anatase crystal type TiO2 nanoparticles (7-8 nm, 12-14 nm, and 17-23 nm) showed more accumulation in the M1 phase of the cell cycle than did the control group. We observed that the TiO2 nanoparticles penetrated zebrafish larvae cells; the anatase type (12-14 nm) penetrated the nucleus, and the rutile type (80-100 nm) penetrated the mitochondria. The results of the present study suggest that the toxic effects of TiO2 nanoparticles on zebrafish embryogenesis depend on the crystalline phase and size of the nanoparticles.