Titanium dioxide nanoparticles induce an adaptive inflammatory response and invasion and proliferation of lung epithelial cells in chorioallantoic membrane.

Titanium dioxide nanoparticles (TiO 2 NPs) studies have been performed using relatively high NPs concentration under acute exposure and limited studies have compared shape effects. We hypothesized that midterm exposure to low TiO 2 NPs concentration in lung epithelial cells induces carcinogenic characteristics modulated partially by NPs shape. To test our hypothesis we synthesized NPs shaped as belts (TiO 2 -B) using TiO 2 spheres (TiO 2 -SP) purchased from Sigma Aldrich Co. Then, lung epithelial A549 cells were low-exposed (10 µg/cm 2 ) to both shapes during 7 days and internalization, cytokine release and invasive potential were determined. Results showed greater TiO 2 -B effect on agglomerates size, cell size and granularity than TiO 2 -SP. Agglomerates size in cell culture medium was 310 nm and 454 nm for TiO 2 -SP and TiO 2 -B, respectively; TiO 2 -SP and TiO 2 -B induced 23% and 70% cell size decrease, respectively, whilst TiO 2 -SP and TiO 2 -B induced 7 and 14-fold of granularity increase. NO x production was down-regulated (31%) by TiO 2 -SP and up-regulated (70%) by TiO 2 -B. Both NPs induced a transient cytokine release (IL-2, IL-6, IL-8, IL-4, IFN-γ, and TNF-α) after 4 days, but cytokines returned to basal levels in TiO 2 -SP exposed cells while TiO 2 -B induced a down-regulation after 7 days. Midterm exposure to both shapes of NPs induced capability to degrade cellular extracellular matrix components from chorioallantoic membrane and Ki-67 marker showed that TiO 2 -B had higher proliferative potential than TiO 2 -SP. We conclude that midterm exposure to low NPs concentration of NPs has an impact in the acquisition of new characteristics of exposed cells and NPs shape influences cellular outcome. [ABSTRACT FROM AUTHOR]