The fate and oxidative stress of different sized SiO2 nanoparticles in zebrafish (Danio rerio) larvae.

Nanoparticle such as silicon dioxide nanoparticles (nano-SiO2) are extensively produced and applied in society. Hence there is an increasing concern about their exposure and toxicity to human and wildlife. To understand the effects of sizes of NPs on their bioavailability and toxicity, zebrafish (Danio rerio) embryos (2 h post-fertilization, hpf) were exposed to 25, 50 and 100 mg/L of 15 or 30 nm nano-SiO2 for 5 days respectively. The results showed that SiO2 could be readily uptaken by zebrafish, and the accumulation of SiO2 was significantly higher in 15 nm treatments groups compared to 30 nm nano-SiO2 treated groups. Furthermore, exposure to 15 nm nano-SiO2 at the concentration of 100 mg/L resulted in more significant changes in reactive oxygen species (ROS) levels, perturbation of lipid peroxidative and antioxidant system than the same concentration of 30 nm nano-SiO2, indicating small sized nano-SiO2 evoked severer oxidative stress in zebrafish larvae. In addition, the more significant up-regulation of transcription of genes related to oxidative stress (e.g., nrf2 and sod1) in 15 nm nano-SiO2 at the 100 mg/L treatments groups provided more evidence for this speculation. Given the above, 15 nm nano-SiO2 were more likely to enter and accumulate in zebrafish larvae, thus causing more serious oxidative stress in vivo. These results may provide additional information on the fate and toxicities of different sizes of NPs.