Bioactive microspheres to enhance sonodynamic-embolization-metalloimmune therapy for orthotopic liver cancer

The development of novel microspheres for the combination of sonodynamic therapy (SDT) with transarterial embolization (TAE) therapy to amplify their efficacy has received increasing attention. Herein, a novel strategy for encapsulating sonosensitizers (e.g., oxygen-deficient manganese tungstate (MnWO_X) nanodots) with gelatin microspheres was proposed. The obtained MnWO_X-encapsulated microspheres (abbr. Mn-GMSs) facilitated efficient sonodynamic-embolization-metalloimmune therapy via the immune effects of metal ions on orthotopic liver cancer tumor after transarterial embolization (TAE). Due to the strong cavitation effect caused by the porous structure, Mn-GMSs exhibited a greater reactive oxygen species (ROS) generation rate than the free MnWO_X nanodots under US irradiation. Efficient SDT revealed robust cell-killing effects and triggered strong immunogenic cell death (ICD). Moreover, the Mn ions released from the bioactive Mn-GMSs further stimulated the dendritic cells (DCs) maturation and triggered the activation of the cGAS/STING pathway to enhance the immunological effect. Thus, Mn-GMSs achieved significant SDT therapeutic outcomes in H22 tumors in mice, and the combination of the Mn-GMSs triggered SDT with programmed cell death ligand 1 (PD-L1) antibodies could further enhance therapeutic outcomes. The Mn-GMSs exhibited high ROS generation efficacy under US irradiation, significant immune activation, good efficacy in combination with immune checkpoint inhibitor, and great potential for artery embolization-assisted drug delivery, thus enabling effective destruction of liver tumors in rats and rabbits. Therefore, this work provides a strategy for applying SDT in deep tumors and highlights a promising sonodynamic-embolization therapy for combating liver cancers.