Scheme 1

Schematic diagram of the antitumor mechanisms of Pd/H-TiO₂-PEG for hypoxia alleviation and enhanced SDT and CDT. a Illustration of the surface reconstruction of TiO₂ caused by H atom adsorption. b The multifunction of Pd/H-TiO₂-PEG including yielding oxygen through Pd catalyzed decomposition of H₂O₂ for hypoxia amelioration, generating •OH through Ti³⁺ mediated Fenton-like reaction for CDT, and producing •OH as well as ¹O₂ through defected TiO₂ sonosensitizer under US irradiation for enhanced SDT. c The in vivo hypoxia amelioration and synergetic enhancement of SDT and CDT for effective tumor suppression