A Tightly Interlayer Bonded, Synchronously In Situ Co-Injectable, Wet-Adhesive, Hierarchically Biofunctionalized Bilayer Hydrogel for Functional Attachment and Orderly Periodontal Regeneration.

Periodontitis, the sixth most prevalent global disease, causes tooth loss and systemic disorders, imposing a significant global burden. Functional regeneration of the periodontium remains a major challenge due to the hierarchical soft-hard tissue interface and complex spatiotemporal functional demands. In this study, a synchronously in situ co-injectable, interlayer-bonding, and wet-adhesive bilayer hydrogel (Bio-Fun bilayer) consisting of PCAC and PCMC layers is developed. An anti-delamination interface is engineered via polymer chain topological entanglement and dynamic boronate ester and ionic networks, while precise complex viscosity matching enables synchronized microscale laminar co-extrusion. Concurrently, the hydrogel maintains wet adhesion, especially to moist root and bone surfaces. Spatiotemporal biofunctionalization is achieved by loading microRNA-26a liposomes in the PCAC layer to activate Wnt/β-catenin signaling for osteogenesis, and covalently tethering a PDGF-BB mimetic peptide within the PCMC layer to trigger PI3K/Akt-LOX signaling for fibroblast recruitment and functional collagen formation. In vivo, the Bio-Fun bilayer hydrogel achieves integrated regeneration of alveolar bone and aligned periodontal ligament fibers, forming Sharpey's fiber-like structures with firm bone-ligament attachment. Meanwhile, the modular and injectable design might provide broad reference for the reconstruction of periodontal, osteochondral, and other soft-hard tissue interfaces.