Titanium-based sonosensitizers for sonodynamic cancer therapy

Sonodynamic therapy (SDT) is a new cancer treatment strategy that uses ultrasound (US) to trigger sonosensitizers to produce a large amount of reactive oxygen species (ROS) to kill malignant tumors, which features outstanding penetrating-depth in tissues and favorable outcome. In recent years, titanium (Ti)-based nanomaterials, particularly TiO2, along with other newly-developed types (e.g., titanium hydrides, titanium carbides), are a kind of high-efficiency sonosensitizers applied extensively in SDT due to their unique physicochemical properties. Based on these, in this review, we firstly introduce different synthesis approaches and surface modification strategies of Ti-based sonosensitizers. Next, the development of Ti-based sonosensitizers for US-triggered therapy, as well as the representative work of enhanced SDT and combined SDT, including chemotherapy, chemodynamic therapy (CDT), photothermal therapy (PTT), gas therapy, and immunotherapy, are detailedly summarized. In addition, the toxicity issues of Ti-based sonosensitizers with some corresponding solutions are also mentioned simply. Finally, the facing challenges and prospects of Ti-based sonosensitizers for SDT are discussed. This review points out the direction for the future application of Ti-based sonosensitizers in SDT or other types of therapy, which is of important reference significance for tumor treatment or even other diseases.