Defect‐Rich BiO₂₋ x ‐BP Composite Nanoplatform: A Synergistic Approach for X‐Ray and Near‐Infrared‐Enhanced Cancer Radiodynamic Therapy

Abstract Cancer treatment faces significant challenges, including hypoxia within the tumor microenvironment, which limits the efficacy of conventional therapies. This study introduces a multifunctional nanoplatform comprising defect‐rich BiO₂₋ x and black phosphorus (BP) nanosheets to address this issue. BiO₂₋ x effectively catalyzes the decomposition of tumor‐overexpressed H₂O₂ into oxygen, mitigating hypoxia. Its high atomic number enhances X‐ray absorption, increasing local radiation doses. When combined with BP, BiO₂₋ x forms a heterojunction that produces secondary electrons, generating reactive oxygen species (ROS) like ·OH under X‐ray irradiation. Additionally, under 808 nm near‐infrared (NIR) light, the platform exhibits strong photothermal effects, further enhancing cancer cell apoptosis. In vitro and in vivo experiments demonstrate the nanoplatform's remarkable ability to synergize radiotherapy, photothermal therapy, and radiodynamic therapy, resulting in significant tumor suppression without adverse effects on major organs. This innovative approach highlights the potential of BiO₂₋ x ‐BP composites for addressing hypoxia and achieving multimodal cancer therapy.