Enhanced OH radical generation by dual-frequency ultrasound with TiO _2 nanoparticles: Its application to targeted sonodynamic therapy

摘要

The present study demonstrated the enhanced hydroxyl (OH) radical generation by combined use of dual-frequency (0.5 MHz and 1 MHz) ultrasound (US) and titanium dioxide (TiO_2) nanoparticles (NPs) as sonocatalyst. The OH radical generation became the maximum, when 0.5 MHz US was irradiated at an intensity of 0.8 W/cm2 and 1 MHz US was irradiated at intensities at 0.4 W/cm2 in the presence of TiO_2 NPs under the examined conditions. After incorporation of TiO_2 NPs modified with targeting protein pre-S1/S2, HepG_2 cancer cells were subjected to the dual-frequency US at optimum irradiation intensities ("targeted-TiO_2/dual-US treatment"). Growth of the HepG_2 cells was reduced by 46% compared with the control condition after irradiation of dual-frequency US for 60 s with TiO _2 NPs incorporation. In contrast, HepG_2 cell growth was almost the same as that in the control condition when cells were irradiated with either 0.5 MHz or 1 MHz ultrasound alone without TiO_2 NP incorporation.