Amorphous silica nanoparticles do not induce cytotoxicity, cell transformation or genotoxicity in Balb/3T3 mouse fibroblasts

Although amorphous silica nanoparticles (aSiO(2)NPs) are believed to be non-toxic and are currently used in several industrial and biomedical applications including cosmetics, food additives and drug delivery systems, there is still no conclusive information on their cytotoxic, genotoxic and carcinogenic potential. For this reason, this work has investigated the effects of aSiO(2)NPs on Balb/3T3 mouse fibroblasts, focusing on cytotoxicity, cell transformation and genotoxicity. Results obtained using aSiO(2)NPs, with diameters between 15 nm and 300 nm and exposure times up to 72 h, have not shown any cytotoxic effect on Balb/3T3 cells as measured by the MTT test and the Colony Forming Efficiency (CFE) assay. Furthermore, aSiO(2)NPs have induced no morphological transformation in Balb/3T3 cells and have not resulted in genotoxicity, as shown by Cell Transformation Assay (CIA) and Micronucleus (MN) assay, respectively. To understand whether the absence of any toxic effect could result from a lack of internalization of the aSiO(2)NPs by Balb/3T3 cells, we have investigated the uptake and the intracellular distribution following exposure to 85 nm fluorescently-labelled aSiO(2)NPs. Using fluorescence microscopy, it was observed that fluorescent aSiO(2)NPs are internalized and located exclusively in the cytoplasmic region. In conclusion, we have demonstrated that although aSiO(2)NPs are internalized in vitro by Balb/3T3 mouse fibroblasts, they do not trigger any cytotoxic or genotoxic effect and do not induce morphological transformation, suggesting that they might be a useful component in industrial applications. (C) 2011 Elsevier B.V. All rights reserved.