Palladium-Based Nanocomposites Remodel Osteoporotic Microenvironment by Bone-Targeted Hydrogen Enrichment and Zincum Repletion

Osteoporosis presents a marked global public health challenge, characterized by deficient osteogenesis and a deteriorating immune microenvironment. Conventional clinical interventions primarily target osteoclast-mediated bone damage, yet lack a comprehensive therapeutic approach that balances bone formation and resorption. Herein, we introduce a bone-targeted nanocomposite, A-Z@Pd(H), designed to address these challenges by integrating diverse functional components. The nanocomposite incorporates internal hydrogen-carrying nanozymes, which effectively scavenge multiple reactive oxygen species (ROS) and synergistically engage the autophagy-lysosome pathway to accelerate endogenous ROS degradation in macrophages. This mechanism disrupts the vicious cycle of autophagic dysfunction-ROS accumulation-macrophage inflammation. In addition, external metal-organic frameworks release zinc ions (Zn²⁺) in response to the acidic osteoporotic environment, thereby promoting osteogenesis. In a murine model of osteoporosis, intravenous administration of A-Z@Pd(H) leads to preferential accumulation in the femur, thereby remodeling the osteoporotic microenvironment through immune regulation, osteogenesis promotion, and osteoclast inhibition. These findings suggest that this system composed of hydrogen therapy and ion therapy may be a promising candidate for bone-targeted comprehensive therapy in osteoporosis.