Design and Fabrication of Low-Temperature 3D-Printed Bioactive Polyurethane/MnO₂ Scaffolds for Bone Repair

Bone defect repair presents a significant clinical challenge, especially for critical-sized defects, due to the limitation of conventional 3D-printed scaffolds to provide simultaneous mechanical support and bioactivity. Herein, this study developed a bioactive composite scaffold through a low-temperature rapid prototyping (LT-RP) 3D printing technology. The scaffold comprises a polyurethane (PU) matrix enhanced with bioactive manganese dioxide (MnO₂) nanoparticles, combining structural integrity with versatile bioactivity for bone repair. By incorporating 2, 6-pyridinedimethanol (PDM) into the PU molecular network, a coordination system is formed, enabling homogeneous distribution and structural integration of MnO₂ nanoparticles. As designed, the bioactive scaffolds are fabricated through LT-RP 3D printing technology with a regular porous architecture for improving cell growth. With 10 wt% MnO₂, the scaffolds (PPM10) have optimal comprehensive properties, with a modulus of ~14.1 MPa, improved thermal stability, good cytocompatibility, and enhanced osteogenic differentiation. Furthermore, in vitro degradation tests revealed the responsive release of Mn²⁺ from the PPM10 scaffolds in a glutathione-rich microenvironment. This functionality indicates the potential of the scaffolds to modify the tumor microenvironment for ultimate bone regeneration after bone tumor surgery.