A p-n heterojunction sonosensitizer for improved sono-immunotherapy via induction of multimodal cell death mechanisms

<b>Rationale:</b> Activating a robust immune system is a crucial strategy for combating solid tumors and preventing recurrences. Studies have shown that cuproptosis and the resulting increased reactive oxygen species (ROS) can trigger immunogenic cell death (ICD) and modulate the tumor immune microenvironment, thereby activating systemic immunity. Therefore, for this purpose, it is important to design a multifunctional copper-based nanomaterial. <b>Method:</b> In this study, we developed Bi₂O_3-XS_X-CuS p-n heterojunction nanoparticles (BCuS NPs) designed to stimulate systemic immune responses and effectively suppress both dormant and recurrent tumors. BCuS nanoparticles were characterized using transmission electron microscopy, X-ray diffraction, and other methods. In addition, the sonodynamic and chemodynamic properties of BCuS were intensively studied by various experimental methods. We identified the mechanisms by which BCuS induced multiple paths of cell death, by using <i>in vitro</i> experiments, including immunofluorescence assays, western blotting, and cell flow cytometry. In addition, we used mouse orthotopic and distal tumor models and RNA sequencing to evaluate the efficacy of combination therapy. <b>Results:</b> The results showed that BCuS produced a Fenton-like reaction in an acidic environment and induced the production of highly toxic ROS during ultrasound treatment. <i>In vitro</i> studies further showed that BCuS induced the occurrence of cuproptosis and ferroptosis, and stimulated ICD in combination with ROS, thereby effectively reversing the immunosuppression of the tumor microenvironment, and improving the sensitivity of immunotherapy. As demonstrated by <i>in vitro</i> studies, <i>in vivo</i> experiments also confirmed the enhanced effects of combination therapy. <b>Conclusion:</b> The BCuS sonosensitizer showed sonodynamic therapy effects, including inhibition of tumor growth in combination with multiple cell death modalities. These findings provide a novel method for using nanomaterials for multimodal combination cancer therapy.