Exploring the role of sonoluminescence in sonodynamic therapy

Sonodynamic therapy, using ultrasound in combination with microbubbles and drugs such as Rose Bengal to achieve a therapeutic outcome, has been demonstrated as an effective method for delivering targeted cancer treatment. One proposed explanation for how sonodynamic therapy achieves its therapeutic effect is that bubbles cavitating under ultrasonic stimulation produce light, sonoluminescence, which then stimulates photo-active drugs. These drugs then produce reactive oxygen species (ROS) leading to localized cell death. Through repeated measurements using multiple techniques, we have shown that the actual amount of light produced by bubble cavitation is several orders of magnitude lower than the level required to produce a therapeutic effect in photodynamic therapy. Additionally, measurement of the levels of ROS produced during established treatment regimens is insufficient to cause significant effects on cell viability. It is therefore unlikely that sonoluminescence and subsequent ROS generation play any significant role in the therapeutic effect of sonodynamic therapy.