Abstract
Osteochondral (OC) defects represent a significant clinical challenge due to the complex, stratified nature of the native tissue, which transitions from a highly compliant cartilaginous surface to a stiff, mineralized subchondral bone. Traditional monophasic scaffolds often fail to replicate this mechanical and biological gradient, leading to poor interfacial integration and functional failure. In this study, we developed a multi-material, extrusion-based 3D bioprinting strategy to fabricate triphasic scaffolds with graded mechanical properties. The design incorporates a polycaprolactone (PCL) and hydroxyapatite (HA) composite for the osseous phase, a gelatin methacryloyl (GelMA)-alginate hydrogel for the cartilaginous phase, and a hybrid transition zone. Mechanical characterization demonstrated a compressive modulus gradient ranging from 185 MPa in the osseous base to 1.2 MPa in the superficial layer, mimicking the native OC unit. Rheological analysis confirmed high shape fidelity of the bioinks, while SEM imaging revealed seamless integration between the thermoplastic and hydrogel layers. Biological assessment using human mesenchymal stem cells (hMSCs) and chondrocytes showed high cell viability (>92%) and zone-specific extracellular matrix deposition over 21 days. These results suggest that spatially controlled multi-material bioprinting provides a robust platform for engineering biomimetic OC tissues with improved structural integrity and regenerative potential. This approach addresses the limitations of abrupt material interfaces, offering a promising solution for the long-term repair of articular joint defects as of early 2024.