Enhanced OH radical generation by dual-frequency ultrasound with TiO2 nanoparticles: Its application to targeted sonodynamic therapy

Abstract

The present study demonstrated the enhanced hydroxyl (OH) radical generation by combined use of dual-frequency (0.5MHz and 1MHz) ultrasound (US) and titanium dioxide (TiO2) nanoparticles (NPs) as sonocatalyst. The OH radical generation became the maximum, when 0.5MHz US was irradiated at an intensity of 0.8W/cm2 and 1MHz US was irradiated at intensities at 0.4W/cm2 in the presence of TiO2 NPs under the examined conditions. After incorporation of TiO2 NPs modified with targeting protein pre-S1/S2, HepG2 cancer cells were subjected to the dual-frequency US at optimum irradiation intensities (“targeted-TiO2/dual-US treatment”). Growth of the HepG2 cells was reduced by 46% compared with the control condition after irradiation of dual-frequency US for 60s with TiO2 NPs incorporation. In contrast, HepG2 cell growth was almost the same as that in the control condition when cells were irradiated with either 0.5MHz or 1MHz ultrasound alone without TiO2 NP incorporation.