Biodegradable persistent ROS-generating nanosonosensitizers for enhanced synergistic cancer therapy by inducing cascaded oxidative stress

Sonodynamic therapy (SDT) is gaining popularity in cancer treatment due to its superior controllability and high tissue permeability. Nonetheless, the efficacy of SDT is severely diminished by the transient generation of limited reactive oxygen species (ROS). Herein, we introduce an acid-activated nanosonosensitizer, CaO₂@PCN, by the controllable coating of porphyrinic metal-organic frameworks (PCN-224) on CaO₂ to induce cascaded oxidative stress in tumors. The PCN-224 doping can generate ROS during SDT to induce intracellular oxidative stress and abnormal calcium channels. Meanwhile, the ultrasound also promotes extracellular calcium influx. In addition, CaO₂@PCN sequentially degrades in the tumor cell lysosomes, releasing Ca²⁺ and H₂O₂ to induce further abnormal calcium channels and elevate the levels of Ca²⁺. Insufficient catalase (CAT) in tumor cells promotes intracellular calcium overload, which can induce persistent ROS generation and mitochondrial dysfunction through ion interference therapy (IIT). More importantly, PCN-224 also protects CaO₂ against significant degradation under neutral conditions. Hence, the well-designed CaO₂@PCN produces synergistic SDT/IIT effects and persistent ROS against cancer. More notably, the acidity-responsive biodegradability endows CaO₂@PCN with excellent biosafety and promising clinical potential.