Comparison of Genotoxicity and Pulmonary Toxicity Study of Modified SiO2 Nanomaterials

Surface-modified nano-SiO2 is a common additive in many products. However, the safety of nano-SiO2 products under various modifications is still unclear. In this study, we investigated the genotoxicity and acute pulmonary toxicity of nano-SiO2 with or without modification. The samples used in this study included: sample A (SA, 55.16 nm, 411.3 mg/mL), modified sample A (mSA, 82.29 nm, 37.7 mg/mL), sample B (SB, 22 nm, 358.0 mg/mL), and modified sample B (mSB, 86.64 nm, 37.7 mg/mL). In the genotoxicity study, we conducted an Ames test, chromosomal aberration test (CA), and a micronucleus (MN) test. The SA, mSA, and mSB groups showed negative results in all these genotoxicity tests. Only SB showed a weakly positive reaction in these assays, but the genotoxicity could be reversed after S9 metabolism or modification. In the acute pulmonary toxicity test, the rats were given an intratracheal instillation (IT) (0.5 mL/kg) of diluted samples and sacrificed after 1 or 14 days. The mortality rate, number of leukocytes and cytokines of TNF-α in the bronchoalveolar lavage fluid (BALF), and the pathology in the lungs were determined. The results revealed that mSA posed acute toxicity in rats. After modification, the pulmonary toxicity was increased in mSA but decreased in mSB on Day 1, and no significant difference was observed on Day 14. In conclusion, there was no observed genotoxicity in either SA or SB, while mSA posed acute inhalation toxicity to rats that decreased in mSB after modification. This indicates that the decrease in pH level in SA and decrease in the solid content in SB are considered after the trifluorosilane surface-modified amorphous nano-silica.