Bilayer book- like decellularized extracellular matrix scaffold with bioactive coatings for rotator cuff repair

Repairing the tendon-bone interface after rotator cuff injury and regulating the local immune microenvironment present significant clinical challenges, necessitating the development of bioactive materials capable of simultaneous interface repair and inflammation modulation. In this study, we developed a book-like scaffold (dtECM-TAZn/Mg) with bilayers of bioactive coatings to target the bone microenvironment and promote rotator cuff repair. Fabricated from decellularized tendon extracellular matrix (dtECM) to preserve native collagen fiber alignment, the scaffold underwent covalent cross-linking of a tannic acid (TA) coating onto its surface. Subsequent incorporation of Zn²⁺ and Mg²⁺ ions established bioactive coatings via metal-phenol coordination bonds formed through polyphenol-metal ion self-assembly and π-π interactions between phenolic molecules. The dtECM-TAZn/Mg scaffold promoted subchondral bone regeneration at the tendon-bone interface via Zn²⁺ release, thereby enhancing structural repair. Concurrently, the synergistic release of TA and Mg²⁺ scavenges reactive oxygen species (ROS) and polarizes macrophages toward the anti-inflammatory M2 phenotype, effectively modulating the local bone microenvironment. This book-like scaffold with dual-layer bioactive coatings for targeted regulation effectively promoted the repair of the tendon-bone interface in rotator cuff injuries.