Engineering triple-layer gelatin methacryloyl–alginate osteochondral construct with biomimetic curved architecture using a multi-axial, multi-process, multi-material 3D bioprinting system

Osteochondral defects caused by trauma, obesity, tumors, and degenerative osteoarthropathies severely impair patients' quality of life. Multilayer tissue engineering scaffolds offer promising strategies for osteochondral repair by enhancing structural biomimicry. In this study, a triple-layer GelMA-alginate-based osteochondral scaffold (TCOS) was fabricated using an enhanced multi-axis, multi-process, multi-material 3D bioprinting system (MAPM-BPS). The scaffold integrates extrusion and electrospinning to construct three distinct layers: a subchondral bone layer (TCOS-S) promoting angiogenesis, an osteochondral interface layer (TCOS-I) preventing vascular invasion, and a cartilage layer (TCOS-C) with a biomimetic spatially curved structure. Scanning electron microscopy analysis showed that TCOS-I had an average pore size of 1.63 ± 0.85 μm (max: 5.94 μm), smaller than HUVECs (14–15 μm), thus potentially preventing blood vessel ingrowth from TCOS-S into TCOS-C. Mechanical testing revealed that TCOS-C achieved a compressive strength of 64.84 ± 18.13 kPa and a modulus of 27.56 ± 7.87 kPa, within the physiological range of native cartilage. Cell experiments demonstrated favorable biocompatibility. Furthermore, HUVECs cultured on TCOS-S exhibited tubular and mesh-like structures, indicating potential for vascularization. These results suggest that the TCOS scaffold fabricated via MAPM-BPS offers structural, mechanical, and biological advantages for integrated osteochondral regeneration.