Natural-Based Nanocomposite Ink Engineering for Seamless Multi-Material Integration in Extrusion-Based 3D Printing.

Multi-tissue regeneration remains a critical clinical challenge due to the lack of solutions that can replicate the hierarchical heterogeneity of such complex interfaces. While biofabrication approaches, such as extrusion-based, allow replicating robust, biomimetic, and layered designs, constructs are usually hindered by inadequate phase/layer integration, poor filler dispersion, and mismatched rheological and mechanical performances. This study introduces an ink engineering strategy as a solution for integrating natural-based nanocomposites in multi-tissue regenerative approaches. For that, two photocrosslinkable natural matrices: a protein-bovine serum albumin methacrylate (BSAMA), and a polysaccharide-hyaluronic acid methacrylate (HAMA)-are selected for their complementary mechanical and cytocompatibility profiles. Bioactive glass nanoparticles, known for osteoconductive potential, are functionalized and covalently immobilized within both matrices through EDC/NHS chemical coupling. This primary crosslinking enables uniform distribution of inorganic phases, unlocking tuneable rheological properties, adequate for extrusion 3D printing. Then, a secondary crosslinking, leveraging the photo-responsive moieties for post-printing photocuring, enables the obtention of seamlessly integrated robust multi-material constructs. Overall, BSAMA-based inks offer higher cytocompatibility, while HAMA-based inks provide superior mechanical strength. Their combination in multi-material constructs supports hASCs' metabolic activity and proliferation, confirming bioactivity and cytocompatibility; and finite element modeling validates their mechanical performance, supporting clinical potential for multi-tissue regeneration.