Cytotoxicity and DNA damage in mouse macrophages exposed to silica nanoparticles

Silica (SiO 2 ) nanoparticles are being progressively applied in various applications, including cosmetics, food technology, and medical diagnostics.Although crystalline SiO 2 is a known carcinogen, the carcinogenicity of SiO 2 nanoparticles remains unclear.Here, we assessed the cytotoxic effects and DNA injury induced by exposure to various dosages of SiO 2 nanoparticles at 0-2400 mg/mL (0-3200 mg/mL microscale SiO 2 as positive control) for 24 h using RAW264.7 cells, followed by methyl tetrazolium (MTT) assay.Cells were also treated by 31.25, 125, and 500 mg/mL SiO 2 nanoparticles (500 mg/mL microscale SiO 2 as positive control) for 24 h and examined by single cell gel electrophoresis assay (SCEG) and flow cytometry.Outstanding dose-related decline in cell viability was observed with enhancing dosages of SiO 2 nanoparticles by MTT assay.The inhibitory concentration 50% of SiO 2 nanoparticles and microscale SiO 2 was H. Yang et al.Genetics and Molecular Research 15 (3): gmr.1503900516690 and 5080 mg/mL, respectively.The comet rate (comet%), length of tail, the percentage in DNA tail (TDNA%) and olive tail moment (OTM) induced by SiO 2 nanoparticles were significantly increased in comparison with control and microscale SiO 2 at 500 mg/mL.500 mg/mL SiO 2 nanoparticles and microscale SiO 2 caused a significant increase in apoptosis rate, decreased proliferation index and increased cell proportions in G 0 /G 1 phases by contrast to the negative control (P < 0.05).This indicates that SiO 2 nanoparticles are more cytotoxic than microscale SiO 2 particles; they induce DNA injury, increase apoptosis, and decrease the proliferation index in RAW264.7 cells.DNA injury and apoptosis may be involved in reducing cell proliferation.