Ternary Bi₂WO₆/TiO₂-Pt Heterojunction Sonosensitizers for Boosting Sonodynamic Therapy

Engineering Z-scheme heterojunctions represents a promising strategy for optimizing the separation and migration of charge carriers in semiconductor sonosensitizers for enhanced reactive oxygen species (ROS) generation. Nevertheless, establishing a continuous and directional pathway for ultrasonic-induced charge flow in Z-scheme heterojunctions remains a significant challenge. In this study, we present a ternary Bi₂WO₆/TiO₂-Pt heterojunction sonosensitizer achieved through the precise growth of Pt nanocrystals on a directionally assembled Bi₂WO₆/TiO₂ Z-scheme structure. The construction of the Bi₂WO₆/TiO₂-Pt heterojunction involves directional growth of Bi₂WO₆ in situ on the highly exposed (001) crystal facet of TiO₂ nanosheets, followed by the precise deposition of nano Pt on the edge (101) crystal facet. The Z-scheme Bi₂WO₆/TiO₂ in the ternary heterojunction ensures effective electron separation, while the Schottky TiO₂-Pt interface establishes a well-defined charge flow path and robust redox capabilities. Moreover, nano Pt confers the Bi₂WO₆/TiO₂-Pt heterojunction with excellent peroxidase-mimic and catalase-mimic activities, facilitating interactions with endogenous H₂O₂ to produce the hydroxyl radicals and O₂. It effectively alleviates tumor hypoxia and enhances ROS production. This results in significantly higher efficiency in sonodynamically induced ROS generation compared to pure TiO₂ or binary Bi₂WO₆/TiO₂ heterojunctions, as confirmed by DFT theoretical calculation and experiments with both in vitro and in vivo anticancer performance. This study offers valuable insights for designing high-performance Z-scheme sonosensitizer systems.