Intracellular distribution, geno- and cytotoxic effects of nanosized titanium dioxide particles in the anatase crystal phase on human nasal mucosa cells

Nanomaterials are defined as substances with at least one dimension smaller than 100 nm in size and are used for a multitude of purposes. Titanium dioxide nanoparticles (TiO 2-NPs) are an important material used as an additive in pharmaceutical and cosmetic products. Due to their high surface-to-mass index, TiO 2 nanoparticles show different physical and chemical characteristics compared to the bulk substance. The knowledge about geno- or cytotoxic effects of TiO 2-NPs is incomplete since existing studies show contrary results. Human nasal mucosa cells were obtained from 10 donors and exposed to TiO 2-NPs in increasing concentrations of 10, 25, 50 und 100 μg/ml. Transmission electron microscopy (TEM) was applied to document particle morphology and size distribution, the degree of particle aggregation and the distribution of particles in inter- and intracellular spaces. Furthermore, DNA fragmentation and cytotoxicity caused by TiO 2-NPs were evaluated. DNA strand breakage was detected by single-cell microgel electrophoresis (comet) assay. Cytotoxic effects were analyzed by trypan blue exclusion test and fluorescein diacetate (FDA) assay. TiO 2 particles used in this study were mainly nanosized but also showed a strong tendency to aggregate in spite of sonication of the suspension. Particles entered the cytoplasm in 11% and the cell nucleus in 4%. The trypan blue exclusion test and the FDA assay did not show any loss of cell viability. In the comet assay, there was no evidence of increased DNA damage for TiO 2-NPs. In this pilot project, no cyto- or genotoxic effects could be shown for TiO 2-NPs on human nasal epithelial cells. Further investigations will focus on a variety of metal oxide nanoparticles to describe the biocompatibility in the human organism.