Anion exchange regulated charge separation engineering in bismuth nanoflowers for sonocatalytic radio-immunotherapy

Ultrasound and X-ray are considered potential options in cancer therapy due to their superior tissue penetration capabilities. Developing effective radiosensitizers is crucial for advancing cancer treatment as they enhance the effectiveness of radiation and sonodynamic therapies while minimizing their side effects. This study aimed to design a degradable bismuth-based heterojunction BiF₃-Bi₂O_3-x:S_x-PEG (BFOSP) radiosensitizer using anion-exchange-regulated charge separation engineering. The heterojunction regulated the bandgap, improved charge carrier mobility, and enhanced reactive oxygen species generation efficiency by introducing O and S anions, enhancing the synergistic effects of sonodynamic therapy and radiotherapy. Sonodynamic therapy reduces the required radiotherapy dose, thus improving the synergistic therapeutic efficacy while enhancing treatment safety. The degradation and oxidative stress effects of BFOSP further disrupted redox balance in the tumor microenvironment while inducing tumor cell apoptosis, ferroptosis, and immunogenic cell death, activating systemic immune responses. This study introduces a reasonable design strategy for degradable radiosensitizers, offering a promising approach to improving synergy and advancing comprehensive cancer therapy.