Study the Cytotoxicity and Genotoxicity of TiO2 Nanoparticles in Human Cells

Along with rapid development of nanotechnology, extensive applications of nanomaterials have been carried out in diverse aspects. Among them, titanium dioxide nanoparticles provide most widespread applications and they are the most common nanomaterials. Because of the nano scale, nanomaterials are substantially different in specific physical and chemical properties from those bulk materials of the same composition. These characteristics allow excellent development and application of nanomaterials; yet the adverse effects on human health may also be generated possibly. According to past literatures, it has been known that titanium dioxide nanoparticles could cause cell damage, apoptosis and inflammatory response. In this study, a human lymphoblastoid cell line (TK6), and a human pulmonary epithelial cell line (A549) were used to determine possible cytotoxicity and genotoxicity induced by titanium dioxide nanoparticles, which have been used most extensively. It was expected to provide relevant information about biohazard of nanomaterials and to facilitate safer development of nanotechnology. In this study, human cell lines were exposed to titanium dioxide nanoparticles of 40 nm in anatase. After 24 hours, Colony formation assay and MTT assay were used to assess cytotoxicity derived from exposure of titanium dioxide nanoparticles. DNA microarray is mainly applied as a high-throughput analysis for expression levels of a large quantity of genes, which allocates a very convenient, fast and reliable method to find out the mechanism of specific genes. At the same time, DNA microarray was used to analyze the genotoxicity induced by titanium dioxide nanoparticles. It was expected to determine specific genes induced by nanoparticles, so as to find out detectable biomarkers of the genotoxicity induced by titanium dioxide nanoparticles, and to further study on influence of titanium dioxide nanoparticles towards physiological mechanism of human cells. The results showed that the cytotoxicity of human lymphoblastoid cell line and human pulmonary epithelial cell line derived from exposure of titanium dioxide nanoparticles took longer period of time to appear, and none of the cytotoxicity was shown within short period of time. As for the genotoxicity of human lymphoblastoid cell line and human pulmonary epithelial cell line induced by titanium dioxide nanoparticles, after analysis with DNA microarray, it was found out that titanium dioxide nanoparticles triggered expression of massive amount of cell repair genes and apoptosis-related genes. The expression of some genes related to balance of oxidative stress and inflammatory response in cells were also observed at the same time. The results showed that exposure of titanium dioxide nanoparticles resulted in increase of oxidative stress of cells and further damage to cells, which may even induced inflammatory response at the end. The results obtained from this study still need to be further researched and discussed. On the other hand, after observation on size and appearance of titanium dioxide nanoparticles, it was discovered that the titanium dioxide nanoparticles would aggregate into larger particles in an extremely rapid manner. Such characteristics are obstacles for traditional method of animal and cell experiments on assessing possible toxic influence induced by nanoparticles. Therefore, the traditional methods of experiments still need to be reviewed and modified, so they can be actually applicable to toxicity test of nanoparticles.