Physico-chemical characteristics and cyto-genotoxic potential of ZnO and TiO2 nanoparticles on human colon carcinoma cells

The aim of the present study is to investigate the role of the physico-chemical properties of ZnO and TiO2 NPs in the potential cytotoxicity, genotoxicity and oxidative DNA damage induction on Caco-2 cell line. As negative control, fine TiO2 particles were used. The characterization of particles was carried out by electron microscopy (SEM, TEM) using a Soft Imaging System. To evaluate the effects of ZnO and TiO2 NPs induced on Caco-2 viability, Neutral Red assay was performed after treatment with different particle concentrations. Our results showed a significant dose and time dependent effect after treatment with ZnO NPs. On the contrary, no effect was observed on Caco-2 cells exposed to TiO2 particles either in micro-and in nano-size. The role of surface in the cytotoxicity induced on Caco-2 was also considered. The levels of DNA 8-oxodG, as the main marker of oxidative DNA damage, were measured by high-performance liquid chromatography with electrochemical detection (HPLC/EC). A significant increase in the 8-oxodG levels was observed after 6 h exposure for both NPs. The estimation of the potential genotoxicity of the two NPs is ongoing by the cytokinesis-block micronucleus assay. Our preliminary results showed that a slight micronucleus increase in binucleated cells was detected in the dose range applied only for ZnO.