Oxidative stress caused by TiO 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 (TiO). It has a catalytic activity and UV absorption, and generates reactive oxygen species (ROS). This catalytic activity of TiO nanoparticles was believed to be capable of killing a wide range of microorganisms. In the environment, the unique properties of TiO nanoparticles can be maintained; therefore, the increasing use of TiO nanoparticles is raising concerns about their environmental risks. Thus, assessment of the biological and ecological effects of TiO-NOAAs is necessary. In this study, we assessed the effect of TiO-NOAAs for S. cerevisiae using DNA microarray. To compare yeast cells under various conditions, six treatment conditions were prepared (1. adsorbed fraction to TiO-NOAA under UV; 2. non-adsorbed fraction to TiO-NOAA under UV; 3. adsorbed fraction to TiO-NOAA without UV; 4. non-adsorbed fraction to TiO-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 TiO-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 TiO-NOAAs on yeast cells under UV irradiation is not caused by TiO-NOAA but UV irradiation.