Fabricating a chitosan-based human placenta extract–encapsulated elastic zonal-structured scaffold for osteochondral applications

Articular cartilage is an avascular and multilayer tissue with limited self-regenerating properties. 3D printing offers a promising approach for fabricating intricate structures that closely replicate the architecture and functional properties of native cartilage. In this study, we fabricated a four-layer 3D-printed thermoplastic polyurethane (TPU) scaffold with varying porosities, ranging from the lowest porosity at the bottom to the highest at the top, to mimic the mechanical properties of cartilage layers from the deep zone to the transition zone. An injectable hydrogel consisting of chitosan (CS) and human placenta extract (HPE) was injected into the 3D-printed scaffold to provide a growth factor-loaded, extracellular matrix (ECM)-mimicking environment with suitable cytocompatibility, aiming to enhance the low cellular activity of the TPU scaffold. An electrospun layer was used as the superficial layer of the scaffold to replicate the longitudinal orientation of collagen fibers at the cartilage surface. Mechanical analysis demonstrated zonal strain distribution in the scaffold similar to native cartilage tissue. The antibacterial assay demonstrated the bactericidal effects of CS and HPE, showing an inhibition zone of (2.892 ± 0.103 mm). The MTT assay quantitatively evaluated the cellular functionality of scaffolds, demonstrating sustained cell viability over 7 days. These combined features make this scaffold design an exceptional candidate for cartilage tissue regeneration applications.