Study on Controllable Preparation of Silica Nanoparticles with Multi-sizes and Their Size-dependent Cytotoxicity in Pheochromocytoma Cells and Human Embryonic Kidney Cells

High-tech products made by nano-materials are tightly connected to people’s life. However environmental impacts and health effects of nanoparticles are widely getting attention. In this paper, we focused on the potential size-dependent cytotoxicity of nanomaterials. Silica (SiO2 )n anoparticles were used as model material. The ion exchange method and modified St ¨ Ober method were used to controllably prepare monodisperse uniform silica nanoparticles with six types of size (20, 50, 80, 140, 280 and 760 nm). And the 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide (MTT) assay and cellular morphology were introduced to evaluate the effect of the six sizes SiO2 nanoparticles on pheochromocytoma (PC12) and human embryonic kidney (HEK293) cells viability. The results indicated that nanosized-SiO2 (20, 50 and 80 nm) caused more cell damage when compared with microsized-SiO2 (140, 280 and 800 nm). IC50 of 24 hr exposure in PC12 cells were 118.2 ± 7.3, 320.4 ± 9.8, and 380.7 ± 10.5µg/ml, and in HEK293 cells were 80.2 ± 6.4, 140.3 ± 9.6 and 309.2 ± 11.3µg/ml for 20, 50- and 80-nm SiO2 particles, respectively. Additionally, the SiO2 particles of the other three sizes over 80-nm had little influence on the cell viability at the concentrations below 2000µg/ml for two cultured cells. The results suggested that the exposure of SiO2 nanoparticles with different sizes leaded to cellular morphological modifications and apoptosis in a size-dependent manner. Further studies on the molecular mechanisms of apoptosis and the toxicity in vivo are necessary.