Amorphous calcium phosphate, Soft‐hard interface, Tissue integration, Tendon‐bone interface, Tendon intrafibrillar mineralization, Science

Abstract Soft and hard tissues possess distinct biological properties. Integrating the soft‐hard interface is difficult due to the inherent non‐osteogenesis of soft tissue, especially of anterior cruciate ligament and rotator cuff reconstruction. This property makes it difficult for tendons to be mineralized and integrated with bone in vivo. To overcome this challenge, a biomimetic mineralization strategy is employed to engineer mineralized tendons. The strategy involved infiltrating amorphous calcium phosphate precursors into collagen fibrils, resulting in hydroxyapatite deposition along the c‐axis. The mineralized tendon presented characteristics similar to bone tissue and induced osteogenic differentiation of mesenchymal stem cells. Additionally, the interface between the newly formed bone and tendon is serrated, suggesting a superb integration between the two tissues. This strategy allows for biomineralization of tendon collagen and replicating the hallmarks of the bone matrix and extracellular niche, including nanostructure and inherent osteoinductive properties, ultimately facilitating the integration of soft and hard tissues.