Sonodynamic therapy information

Sonodynamic therapy (SDT) is a noninvasive treatment, often used for tumor irradiation, that utilizes a sonosensitizer and the deep penetration of ultrasound to treat lesions of varying depths by reducing target cell number and preventing future tumor growth.^[1][2] Many existing cancer treatment strategies cause systemic toxicity or cannot penetrate tissue deep enough to reach the entire tumor; however, emerging ultrasound stimulated therapies could offer an alternative to these treatments with their increased efficiency, greater penetration depth, and reduced side effects. Sonodynamic therapy could be used to treat cancers and other diseases, such as atherosclerosis, and diminish the risk associated with other treatment strategies since it induces cytotoxic effects only when externally stimulated by ultrasound and only at the cancerous region, as opposed to the systemic administration of chemotherapy drugs.^[3][4][5]

Reactive oxygen species (ROS) are an essential component of SDT as they provide the cytotoxicity of sonodynamic therapy; they are produced when ultrasound is coupled with a sensitizing drug and molecular oxygen.^[1] Without ultrasound, the drug is not toxic. However, once the drug is exposed to ultrasound and molecular oxygen, it becomes toxic.^[1] Photodynamic therapy, from which sonodynamic therapy was derived, uses a similar mechanism. Instead of ultrasound, light is used to activate the drug.^[1] SDT allows the ultrasound to reach deeper into the tissue (to about 30 centimeters) compared to photodynamic therapy (PDT) since it can be highly focused.^[1] This increased penetration depth ultimately means that SDT can be utilized to treat deeper, less accessible tumors and is more cost-effective than PDT.^[6][1] Photodynamic therapy can be used in combination with sonodynamic therapy and is expanded upon in the Applications section of this article. Sonodynamic therapy can be used synergistically with other therapeutic methods such as drug-loaded microbubbles, nanoparticles, exosomes, liposomes, and genes for improved efficacy. Currently, SDT does not have any clinical products and acts as an adjuvant for the aforementioned therapeutic methods, but it has been explored for use in atherosclerosis and cancer treatment to reduce tumor size in breast, pancreas, liver, and spinal sarcomas. ^{[7][3] [8][9][10] [11][12][13] [14][15][16]}