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 TiO_2-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 (~ 10 nm), the in-situ formed TiO_2-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@TiO_2-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. [ABSTRACT FROM AUTHOR]