Oxidative stress caused by TiO2 nanoparticles under UV irradiation is due to UV irradiation not through nanoparticles.

Currently, nanoparticles are used in various commercial products. One of the most common nanoparticles is titanium dioxide (TiO2). It has a catalytic activity and UV absorption, and generates reactive oxygen species (ROS). This catalytic activity of TiO2 nanoparticles was believed to be capable of killing a wide range of microorganisms. In the environment, the unique properties of TiO2 nanoparticles can be maintained; therefore, the increasing use of TiO2 nanoparticles is raising concerns about their environmental risks. Thus, assessment of the biological and ecological effects of TiO2-NOAAs is necessary. In this study, we assessed the effect of TiO2-NOAAs for S. cerevisiae using DNA microarray. To compare yeast cells under various conditions, six treatment conditions were prepared (1. adsorbed fraction to TiO2-NOAA under UV; 2. non-adsorbed fraction to TiO2-NOAA under UV; 3. adsorbed fraction to TiO2-NOAA without UV; 4. non-adsorbed fraction to TiO2-NOAA without UV; 5. under UV; and 6. untreated control). The result of the DNA microarray analysis, suggested that yeast cells that are adsorbed by TiO2-NOAA under UV irradiation suffer oxidative stress and this stress response was similar to that by only UV irradiation. We concluded that the effect of TiO2-NOAAs on yeast cells under UV irradiation is not caused by TiO2-NOAA but UV irradiation.