3D-Printed ThermallyActivated Shape Memory PLA/TBCComposite Scaffold with Body-Compatible Temperature for MinimallyInvasive Bone Repair

Shape memory polymers (SMPs) can transform between initial and programmed shapes under certain stimuli and have promising potential in developing shape-adaptative bone scaffolds to treat irregular bone defects in minimally invasive implantation. Polylactic acid (PLA) is a degradable, biocompatible polymer that has thermal-responsive shape memory properties; however, its high transition temperature (approximately 50–60 °C) limits clinical applicability. This study proposes to develop a shape memory PLA based composite bone scaffold that can be gently thermally driven under a moderate temperature near the body by adding tributyl citrate (TBC) and fabricated via FDM 3D printing. The 3D-printed PLA/TBC composite scaffolds showed ordered porous structures with an orthogonal periodic interconnection. The mechanical test showed that TBC significantly increased the toughness of the scaffolds while it decreased its strength and modulus. The thermal physical property test showed that the glass transition temperature was successfully reduced from 54.9 °C (pure PLA) to 40.2 °C (10% TBC), approaching body temperature through TBC’s plasticization mechanism where low-MW ester molecules increased PLA chain mobility, thereby enhancing their flexibility. The shape memory test showed the shape fixation rate of the PLA/TBC scaffold achieved 97.2% with 10% TBC, and it can transform from programmed shape to initial shape in 30 s with a shape recovery rate of 92.8% under a gentle thermal stimulation at 45 °C. Then, proof of concept of this scaffold for minimally invasive implantation of the irregular bone defect model was presented. Besides, other tests showed that the hydrophilicity and degradation performance of the scaffolds were improved with TBC. Meanwhile, TBC also promoted the biomineralization and cellular response of the scaffold. This study provides an insight for developing shape- and temperature-adaptive bone scaffolds for minimally invasive repair of irregular bone defects.