Bi-Pt Heterojunction Cascade Reaction Platform for Sono-Immunotherapy of Tumors via PANoptosis and Ferroptosis.

Sonodynamic therapy (SDT) represents a promising, noninvasive, and precise treatment modality for tumors, demonstrating significant potential in clinical applications. However, the efficiency of sonosensitizers in generating reactive oxygen species (ROS) is often limited by rapid electron-hole recombination. In this study, BiF@BiOI is synthesized via a co-precipitation method, followed by in-situ reduction to decorate it with Pt nanoparticles, resulting in BiF@BiOI@Pt-PVP (BBP) nanocomposite for enhancing SDT efficacy. The formation of the BiF@BiOI heterojunction enhances charge separation ability. The decoration of Pt nanoparticles narrows the bandgap and alters the band positions and Fermi level of BBP, which can effectively mitigate the rapid recombination of electron-hole pairs and facilitate a cascade reaction of ROS, thereby improving ROS generation efficiency with ultrasound excitation. Additionally, bismuth ions in BBP and the generated holes consume glutathione, exacerbating cellular oxidative damage, and triggering PANoptosis and ferroptosis. Furthermore, Pt nanoparticles demonstrate peroxidase-like activity, catalyzing endogenous hydrogen peroxide to oxygen. These functions are helpful against tumors for alleviating hypoxic conditions, reshaping the microenvironment, modulating immune cell infiltration capacity, and enhancing the efficacy of immunotherapy. The dual strategy of forming heterojunctions and sensitization with noble metals effectively enhances the efficacy of sono-catalytic therapy-induced immune activation in tumor treatment.