Precise Design of TiO2@CoOx Heterostructure via Atomic Layer Deposition for Synergistic Sono‐Chemodynamic Oncotherapy

Abstract Sonodynamic therapy (SDT), a tumor treatment modality with high tissue penetration and low side effects, is able to selectively kill tumor cells by producing cytotoxic reactive oxygen species (ROS) with ultrasound‐triggered sonosensitizers. N‐type inorganic semiconductor TiO 2 has low ROS quantum yields under ultrasound irradiation and inadequate anti‐tumor activity. Herein, by using atomic layer deposition (ALD) to create a heterojunction between porous TiO 2 and CoO x , the sonodynamic therapy efficiency of TiO 2 can be improved. Compared to conventional techniques, the high controllability of ALD allows for the delicate loading of CoO x nanoparticles into TiO 2 pores, resulting in the precise tuning of the interfaces and energy band structures and ultimately optimal SDT properties. In addition, CoO x exhibits a cascade of H 2 O 2 →O 2 →·O 2 − in response to the tumor microenvironment, which not only mitigates hypoxia during the SDT process, but also contributes to the effect of chemodynamic therapy (CDT). Correspondingly, the synergistic CDT/SDT treatment is successful in inhibiting tumor growth. Thus, ALD provides new avenues for catalytic tumor therapy and other pharmaceutical applications.