Targeting Mitochondrial Oxidative Stress by Calcium/Copper/Elesclomol Tri-Overloaded Nanocages for Osteosarcoma Immunotherapy via Immunogenic Cell Death

Osteosarcoma (OS) immunotherapy offers a solution to overcome the limitations of traditional treatments. However, OS is a "cold tumor" due to deletion of the MTAP gene and sparse infiltration of immune cells, exhibiting high immunological tolerance. Here, we construct calcium/copper/elesclomol (Ca²⁺/Cu²⁺/STA-4783) tri-overloaded nanocages (SACCT NCs) to target mitochondrial oxidative stress and induce immunogenic cell death (ICD) for OS immunotherapy. In this pH-responsive nanoplatform, Ca²⁺ and STA-4783 are codelivered to mitochondria, promoting H₂O₂ overexpression via the TCA cycle and SOD1. Subsequently, Cu⁺ released from SACCT NCs effectively catalyzes H₂O₂ into toxic •OH, inducing oxidative stress damage and mitochondrial dysfunction rather than triggering cuproptosis (weak cuproptosis). Meanwhile, increased Cu⁺ levels from transmembrane transport by CTR1 and ATP7A/B enhance intracellular oxidative stress, resulting in the ICD of OS cells. Finally, overexpression of CRT and NLRP3 activates the DCs-CD8⁺ T cell immune response axis through the lymphocyte-mediated immunity pathway, enabling effective immunotherapy. Considering the <i>in vivo</i> pH-responsive biodegradability in the tumor immune microenvironment (TIME), our study has provided an impetus for the design and preparation of copper-based nanomaterials, which are efficacious in OS immunotherapy.