Genotoxicity of different nano-sizes and ions of silica nanoparticles

We have used human peripheral blood lymphocytes and cultured human embryonic kidney (HEK293) cells to study the possible genotoxic potential of different nanosized silicium dioxide or silica nanoparticles (SiO₂ NPs), namely, 6, 15, 30 and 55 nm, and ions with a modified alkaline comet assays with and without the formamidopyrimidineDNA N glycosylase Fpg and endonuclease III (Endo III) enzymes. Modifications to the comet assay by using lesion-specific endonucleases, such as Fpg and Endo III, can detect DNA bases with oxidative damage. SiO₂ NPs were supplied to human cells treated in vitro at concentrations ranging from 1 to 100 μg/ml. Our results show a statistically significant induction in the DNA damage was observed by the comet assay with and without the Fpg and Endo III enzymes in human cells exposed to the highest concentration (100 μg/ml) of different nanosized SiO₂ NPs. As well as, a dose-dependent relationship increase in the DNA damage from the treated cells was observed. Fpg treatment detected more oxidative DNA damage (specifically purine damage) in the different nanosized SiO₂ NPs and ions exposed to both human cell cultures compared to no enzyme treatment (enzyme buffer only). This is the first study reporting genotoxicity data in these human cells for the different nanosized SiO₂ NPs.