Ultrafine Titanium Monoxide (TiO₁₊) Nanorods for Enhanced Sonodynamic Therapy

Ultrasound (US)-triggered sonodynamic therapy (SDT) that enables noninvasive treatment of large internal tumors has attracted widespread interest. For improvement in the therapeutic responses to SDT, more effective and stable sonosensitizers are still required. Herein, ultrafine titanium monoxide nanorods (TiO₁₊ NRs) with greatly improved sono-sensitization and Fenton-like catalytic activity were fabricated and used for enhanced SDT. TiO₁₊ NRs with an ultrafine rodlike structure were successfully prepared and then modified with polyethylene glycol (PEG). Compared to the conventional sonosensitizer, TiO₂ nanoparticles, the PEG-TiO₁₊ NRs resulted in much more efficient US-induced generation of reactive oxygen species (ROS) because of the oxygen-deficient structure of TiO₁₊ NR, which predominantly serves as the charge trap to limit the recombination of US-triggered electron-hole pairs. Interestingly, PEG-TiO₁₊ NRs also exhibit horseradish-peroxidase-like nanozyme activity and can produce hydroxyl radicals (^•OH) from endogenous H₂O₂ in the tumor to enable chemodynamic therapy (CDT). Because of their efficient passive retention in tumors post intravenous injection, PEG-TiO₁₊ NRs can be used as a sonosensitizer and CDT agent for highly effective tumor ablation under US treatment. In addition, no significant long-term toxicity of PEG-TiO₁₊ NRs was found for the treated mice. This work highlights a new type of titanium-based nanostructure with great performance for tumor SDT.