In-situ TiO2-x Decoration of Titanium Carbide MXene for Photo/sono-Responsive Antitumor Theranostics.

Background: Sonodynamic therapy (SDT) has emerged as a noninvasive therapeutic modality that involves sonosensitizers and low-intensity ultrasound. However, owing to the rapid recombination of charge carriers, most of the sonosensitizers triggered poor reactive oxygen species (ROS) generation, resulting in unsatisfactory sonodynamic therapeutic effects. Results: Herein, a photo/sono-responsive nanoplatform was developed through the in-situ systhesis of TiO2-x, on the surface of two-dimensional MXene (titanium carbide,Ti3C2) for photoacoustic/photothermal bimodal imaging-guided near-infrared II (NIR-II) photothermal enhanced SDT of tumor. Because of several oxygen vacancies and smaller size (similar to 10 nm), the in-situ formed TiO2-x nanoparticles possessed narrow band gap (2.65 eV) and high surface area, and thus served as a charge trap to restrict charge recombination under ultrasound (US) activation, resulting in enhanced sonodynamic ROS generation. Moreover, Ti3C2 nanosheets induced extensive localized hyperthermia relieves tumor hypoxia by accelerating intratumoral blood flow and tumor oxygenation, and thus further strengthened the efficacy of SDT. Upon US/NIR-II laser dual-stimuli,Ti3C2@TiO2-x nanoplatform triggered substantial cellular killing in vitro and complete tumor eradication in vivo, without any tumor recurrence and systemic toxicity. Conclusion: Our work presents the promising design of photo/sono-responsive nanoplatform for cancer nanotheranostics.