Effect of Titanium Dioxide Nanoparticles on Reactive Oxygen Species Generation in a High-Frequency Ultrasound Range

We have previously confirmed that reactive oxygen species (ROS) were generated by ultrasound at higher frequencies than conventional frequencies. However, the amount of ROS to use in cancer therapy is insufficient because of the challenge of inducing cavitation by high-frequency ultrasound. In this study, we generated a large amount of ROS in and out of cells by irradiating Titanium dioxide nanoparticles <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\text{TiO}_{2}$</tex> NPs) with high-frequency ultrasound using a lithium niobate (LN) transducer. High-frequency ultrasound irradiation of the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{TiO}_{2}$</tex> NPs diffused in aqueous solution generated several times more ROS inside and outside the cells than in the case without <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{TiO}_{2}$</tex> NPs.