Effect of low doses of TiO2 nanoparticles on HeLa cells

Y. Xu, M-T Wei, H.D. Ou-Yang, H.Z. Wang, C. Gordon, P. Brink, M. Rafailovich, T. Mironava
Stony Brook University,
United States

Keywords: nanotoxicology, titanium dioxide, HeLa cells

Summary:

Titanium dioxide (TiO2) is naturally occurring compound that is generally used as a white pigment due to its brightness and high refractive index. It is among top five nanoparticles (NPs) used in consumer products and accounts for 70% of the total production volume of pigments worldwide. These particles also exhibit photocatalytic activity and have been intensively studied in anti-cancer and anti-bacterial applications. Recently, several research groups reported that TiO2 NPs exhibit toxicity, in the ambient light and dark conditions without exposure to UV light. The detrimental effect are well understood in terms of the reactive ion species formed, which are toxic to both eukaryotic cells and bacteria, when the photoelectron is emitted after irradiation of the TiO2 particles. Yet, in the absence of UV irradiation, TiO2 is reported to be toxic primarily to the eukaryotic cells and not to the bacteria. This can be a cause of possible concern, especially when the cells exposed to particles are also exposed to bacteria. Hence in this study we focused on this situation in two systems (cells and bacteria), where TiO2 particles in conjunction with radiation, have been previously studied separately. The bacterial system we chose is Staphylococcus aureus which is one of the most successful human pathogens with very diverse range of virulence factors and is the leading cause of human infections worldwide. Consequently, it is capable of causing an array of diseases from minor soft tissue infections to life-threatening septicemia. Previous work had shown that these bacteria were highly susceptible to damage by ROS products, and exhibited a well-defined exclusion zone when exposed to high concentrations of TiO2. Since these concentrations are also toxic to cells, we chose to focus on the effects at low concentrations, where ROS production is negligible and which were previously shown not to effect cell proliferation, yet as we will demonstrate, can still have profound effects on cell function and the interaction of the cells with bacteria.