A H₂-bioreactor for mitochondrial rehabilitation in infected bone defects regeneration

The repair of infected bone defects (IBDs) presents a significant clinical challenge due to recurrent infections and inflammation. Characterized by reactive oxygen species (ROS) bursts and mitochondrial dysfunction, IBDs generates to a vicious oxidation-inflammation cycle that impairs bone remodeling. To address this, we developed a double-network hydrogel scaffold composed of phenylboronic acid-modified quaternary chitosan and glycidyl methacrylated poly(vinyl alcohol) (QP-P), crosslinked via dynamic boronic ester bonds and covalent bonds, loaded with magnesium microspheres (Mg spheres) (QP-P/Mg). This double-crosslinking network confers excellent injectability and tissue adhesion while integrating potent antibacterial, ROS-scavenging, pro-angiogenic, and osteogenic functions. Notably, Mg spheres enable controlled hydrolysis through a boronic ester-magnesium ion (Mg²⁺) complexation mechanism, providing sustained release of hydrogen (H₂) and Mg²⁺, with H₂ potently alleviating oxidative stress and restoring mitochondrial homeostasis via the Nrf2/HO-1 pathway and Mg²⁺ promoting vascularized bone regeneration. In a rat IBDs model, QP-P/Mg achieved substantial bone regeneration, with a BV/TV ratio of 45.32 % ± 8.22 % after 4 weeks, representing a 6.27-fold improvement over controls. These findings underscore the potential of this H₂-releasing hydrogel scaffold with multifunctional properties to promote vascularized bone regeneration in IBDs through ROS elimination and mitochondrial rehabilitation, offering promising clinical translational opportunities for the treatment of IBDs.