Multifunctional carbon dot/MXene heterojunctions for alleviation of tumor hypoxia and enhanced sonodynamic therapy

TiO2-based semiconductor nanosonosensitizers have been extensively explored for sonodynamic therapy (SDT) against deep-seated tumors, but their clinical applications are limited by low reactive oxygen species (ROS) quantum yields owing to their rather wide bandgaps (∼3.2 eV). Herein, we report Ti3C2-based two-dimensional (2D) MXene nanosheets with a bandgap of only ∼0.94 eV, induced by surface terminations (-F, –OH), were employed as a novel narrow-bandgap nanosonosensitizer for effective SDT. To improve the stability and SDT performance of the MXene nanosheets, 0D/2D hybrid heterojunctions (HJs) were also introduced between Ti3C2 nanosheets and graphitic N doped carbon dots. Taking the advantage of the HJ-enhanced carrier transfers, the designed [email protected]3C2Tx HJs exhibited a remarkably enhanced ROS generation efficiency, which was 3.07 times than that of commercial TiO2 nanoparticles. The [email protected]3C2Tx HJs were also found to offer enhanced photothermal conversion efficiency in the NIR-II biowindow (64.5%). By using the mild photothermal effect to alleviate tumor hypoxia in the “cold” tumor microenvironment (TME), complete tumor ablation was realized by the mild NIR-II PTT-enhanced deep-tissue SDT. This work presents the promising potential of MXene-based 2D materials for noninvasive SDT of deep-seated tumors.