Three-Dimensional Printing of Biodegradable Piperazine-Based Polyurethane-Urea Scaffolds with Enhanced Osteogenesis for Bone Regeneration

Synthetic biodegradable polymeric scaffolds with uniformly interconnected pore structure, appropriate mechanical properties, excellent biocompatibility, and even enhanced osteogenesis ability are urgently required for in situ bone regeneration. In this study, for the first time, a series of biodegradable piperazine (PP)-based polyurethane-urea (P-PUU) scaffolds with a gradient of PP contents were developed by air-driven extrusion 3D printing technology. The P-PUU ink of 60 wt % concentration was demonstrated to have appropriate viscosity for scaffold fabrication. The 3D-printed P-PUU scaffolds exhibited an interconnected porous structure of about 450 μm in macropore size and about 75% in porosity. By regulating the contents of PP in P-PUU scaffolds, their mechanical properties could be moderated, and P-PUU1.4 scaffolds with the highest PP contents exhibited the highest compressive modulus (155.9 ± 5.7 MPa) and strength (14.8 ± 1.1 MPa). Moreover, both in vitro and in vivo biological results suggested that the 3D-printed P-PUU scaffolds possessed excellent biocompatibility and osteoconductivity to facilitate new bone formation. The small molecular PP itself was confirmed for the first time to regulate osteogenesis of osteoblasts in a dose-dependent manner and the optimum concentration for osteoconductivity was about ∼0.5 mM, which suggests that PP molecules, together with the mechanical behavior, nitrogen-contents, and hydrophilicity of P-PUUs, play an important role in enhancing the osteoconductive ability of P-PUU scaffolds. Therefore, the 3D-printed P-PUU scaffolds, with suitable interconnected pore structure, appropriate mechanical properties, and intrinsically osteoconductive ability, should provide a promising alternative for bone regeneration.