Intracellular Reactive Oxygen Species Generation Induced by High‐Frequency Ultrasound in Thickness Vibration Mode

Reactive Oxygen Species (ROS), which play a critical role in cellular signaling pathways, are one of the chemical products caused by ultrasound irradiation. In general, ROS generation has been ignored in terms of high-frequency ultrasound (>5 MHz) due to the limitation of cavitation induction. However, does high-frequency ultrasound not affect the production of ROS in cells? Here, we propose comparing ROS in solution and intracellular ROS generation by ultrasound at high frequency (6.5 MHz) and at a common frequency (1 MHz) in medical ultrasound applications, thereby elucidating the capabilities of high-frequency ultrasound on cells by ROS production. We discovered that 6.5 MHz ultrasound, as irradiated by a lithium niobate transducer, generates intracellular ROS more than conventional 1.0 MHz ultrasound. The phenomenon of ROS production by high-frequency ultrasound having high spatial resolution demonstrated the possibility that ultrasound is capable of effectively generating intracellular ROS at the cellular level.