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Current osteochondral (OC) defect repair approaches using premade scaffolds face clinical limitations due to invasiveness, weak integrity, and/or insufficient interfacial bonding. An injectable hydrophobic laminous adhesive is developed that rapidly photocross‐link subaqueously and forms robust bi‐layered structure that orchestrates biophysical‐chemical cues for stimulating OC repair. Liquid hydrophobic photo‐cross‐linkable poly (lactide‐co‐propylene glycol‐co‐lactide) dimethacrylates (PmLnDMA) are adopted as cartilage phase and PmLnDMA encapsulating methacrylated hydroxyapatite nanoparticles (PmLnDMA/MH) as the mineralized subchondral bone phase. Both phases exhibit strong interfacial bonding due to the presence of "CC". Mechanotransduction and growth factor‐mediated signaling pathways are enchanced by matching the mechanical properties of two phases to native cartilage and bone via systematical modulation of the adhesives' composition and encapsulated growth factors' release profile. This enhances mesenchymal stem cells' commitment to corresponding chondrocytes and osteoblasts to augment OC repair in vitro and in vivo, and ultimately benefits patients suffering from OC fracture, osteoarthritis, and osteoporosis. [ABSTRACT FROM AUTHOR]

Existing artificial periostea faces difficulty in supporting the entire bone repair cycle due to the absence of adhesion‐centric design and effective cell manipulation, leading to poor inhibition of soft tissue infiltration and induction of osteogenesis and angiogenesis. Here, a Janus periosteum with interior surface adhesion and exterior anatomical patterns to mimic the structure and function of natural periosteum is presented. Photo‐crosslinkable polymers are employed to replicate the exterior anisotropic surface structured microgrooves for cell fate manipulation and assemble gecko‐inspired fibrillar setae arrays for interior surface adhesion. To further bolster its underwater adhesiveness, mussel‐inspired poly (dopamine methacrylamide‐co‐hydroxyethyl methacrylate) (PDMH) is coated onto the periosteum surfaces. This periosteum presents adhesiveness with strong shear and normal adhesion in both dry and wet conditions due to the coordinated interactions of micro setae arrays and PDMH coating; it also boasts effective cell modulation for enhanced synchronous osteogenesis and angiogenesis, without the aid of growth factors. Moreover, the Janus periosteum is found to enhance bone regeneration in vivo with increased new bone formation and neovascularization. It is envisioned that this Janus periosteum will be able to streamline bone fracture surgical repair as a rapidly adhesive, low‐maintenance yet robust bandage to significantly cut down the healing phase. [ABSTRACT FROM AUTHOR]