Citotoxicidade e genotoxicidade de nanopartículas de dióxido de titânio em células de mamíferos

Abstract

Titanium dioxide (TiO2) is a metal oxide readily found in nature and widely used in pigments because of the ability to provide whiteness and opacity. The progress of nanotechnology, titanium dioxide at the nanoscale (TiO2NP) has also been applied as an opacifier in fabrics, glass, porcelain, pharmaceuticals and cosmetics. In addition, it has photocatalytic and antibacterial properties. Moreover, TiO2NP can be applied as delivery of substances, food additives to improve the growth of cattle and increase protein synthesis in animals. Due to the increased application of TiO2NP and increasing exposure, grow the necessity to know the behavior and risk of TiO2NP. Therefore, the objective of this study is to evaluate the in vitro toxicity of titanium dioxide nanoparticles in mammalian cells (Chinese Hamster ovary epithelium – CHO and bovine fibroblast). TiO2NP were characterized by dynamic light scattering (DLS) in order to know the Zeta Potential, hydrodynamic size and polydispersity index; by atomic force microscopy (AFM) to know the shape and size; and by infrared and RAMAN spectroscopy for the chemical composition. Subsequently, cytotoxicity and genotoxicity tests were performed, such as cell morphology evaluation by light microscopy, cell viability by the Methyl Thiazole Tetrazolium (MTT) assay, and oxidative stress by Superoxide Dismutase (SOD) and the micronucleus assay as a test genotoxic. Concentrations of 0,1 μg/mL, 1 μg/mL, 5 μg/mL, 10 μg/mL of TiO2NP were evaluated in all the assays. The analyzes made in DLS with TiO2NP in deionized water, culture medium with and without fetal bovine serum, shows that in deionized water and culture medium hydrodynamic size was around 500 and 1300 nm, however in culture medium with fetal bovine serum the size range from 440 nm to 20 nm. The zeta potential in culture medium was around – 14 mV, culture medium with fetal bovine serum was around -21,6 mV and deionized water was around – 4,2 mV. According to AFM the TiO2NPs reveals different geometries and sizes, since cylindrical to a cubic forms. According the MTT method, the exposure of bovine fibroblasts to TiO2NPs did not affect cell viability. We evaluated the activity of the SOD enzyme in CHO cells and bovine fibroblasts, however, none of the TiO2NP concentrations altered the activity of this enzyme (P> 0.05). Based on the MN assay none of the concentrations tested were genotoxic for bovine fibroblasts, however for CHO 0,1 μg/mL TiO2NP in the short and long treatment and 1 μg/mL TiO2NP in the long treatment increased the micronucleus frequency. TiO2NPs were not cytotoxic to bovine fibroblasts, nevertheless, the concentration of 0,1μg/mL of TiO2NP was shown to be cytotoxic and genotoxic (long and short treatment) as well as 1 μg / mL TiO2NP was genotoxic (long treatment) for CHO cells because they alter cell viability and induce micronuclei in these cells.