Engineered Composite Bilayer Scaffold with Functional Osteogenic and Chondrogenic Potential to Repair Articular Cartilage Defect.

Trauma, aging, arthritis, and sports injuries are provoking conditions of osteochondral defects (OCDs). If left untreated, these conditions may affect millions and create a significant socio-economic burden. Repair of osteochondral tissue poses significant challenges owing to its lack of vascularization and intricate zonal architecture, which includes both subchondral bone and superficial cartilage layers. This study aims to fabricate a biomimetic bilayer scaffold for osteochondral defect regeneration, emphasizing the restoration of both chondral and subchondral regions. The subchondral layer was prepared with an inorganic phase (hydroxyapatite and graphene oxide [HAP-GO]), while the cartilage layer was constructed with an organic phase (collagen type I and fibrin [COL-F]) to replicate the native extracellular matrix (ECM) of osteochondral tissue. Structural and physicochemical characterization of the bilayer scaffold demonstrated an integrated layer with appropriate pore sizes, high porosity, and optimal mechanical strength. In vitro evaluations exhibited high biocompatibility and cellular adhesion. Furthermore, the osteoinductive and chondroinductive potential of the scaffold's bone and chondral layers were evaluated at cellular and molecular levels. In vivo studies in a rat model showed significant osteochondral defect regeneration after 12 weeks, evidenced by complete defect closure through macroscopic analysis, X-ray, and microcomputed tomography. Histological and immunohistochemical analyses confirmed collagen and glycosaminoglycan deposition, supporting initial bone and chondral tissue formation. The enhanced healing potential of this cell-free bilayer scaffold suggests it is a promising biomaterial for osteochondral regeneration.