Functionalized Bilayer Scaffold-Mediated Spatio-Temporal Regulation of Regenerative Immune Microenvironment, Endogenous Stem Cell Recruitment, and Differentiation for Osteochondral Repair

Functional regeneration of osteochondral defects remains hindered by poor spatiotemporal coordination, insufficient endogenous stem cell recruitment, oxidative stress, and unresolved inflammatory microenvironments that drive apoptosis. To address this, we designed a magnesium boride (MgB 2)-functionalized bilayer scaffold that orchestrates spatiotemporal control over endogenous repair mechanisms. The upper mimics cartilage ECM that GelDA/HAMA hydrogel establishes a chondroinductive niche by recruiting synovial fluid-derived mesenchymal stem cells (SF-MSCs) via dopamine-mediated adhesion and RGD motifs. The lower 3D-printed MgB 2@PLGA scaffold mimics bone stiffness and releases Mg 2+ and H 2 in a time-dependent manner, scavenging excess ROS during the early inflammatory phase and polarizing macrophages toward an anti-inflammatory M2 phenotype. The GelDA/HAMA hydrogel enhances stem cell adhesion and extracellular matrix remodeling to establish a pro-regenerative microenvironment. Sustained Mg 2+ release subsequently drives SF-MSC chondrogenesis and bone BMSC osteogenic mineralization. In a rabbit full-thickness osteochondral defect model, the scaffold promoted hyaline-like cartilage regeneration and subchondral bone mineralization at 6 and 12 weeks, with higher collagen II deposition at the integration interface compared to controls. This study presents a cell- and growth factor-free strategy that leverages the multifunctional biological properties of MgB 2 to spatiotemporally coordinate immunomodulation, redox homeostasis, and dual-lineage differentiation.