Homogeneous distribution of Fe₃O₄ nanoparticles in poly(L-lactic acid)/thermoplastic polyurethane bone scaffold for...

The primary consideration of a 4D printed bone scaffold is possessing good shape memory properties, followed by choosing an appropriate stimulation. Herein, polydopamine was coated on the surface of Fe₃O₄ to improve its distribution and dispersion in the 4D printed porous poly(L-lactic acid)/thermoplastic polyurethane (PLLA/TPU) composite bone scaffold, with enhanced magnetic-response shape memory properties. Specifically, the ratio of PLLA and TPU was optimized to 5:5, achieving optimal shape memory properties with a co-continuous structure. Subsequently, Fe₃O₄ coated with different polydopamine thicknesses was added at the same content. When the polydopamine thickness was too low (2 nm) or too thick (10 nm), it could not effectively promote the dispersion of Fe₃O₄ or prevent the original co-continuous structure from being disrupted. Only when the polydopamine coating thickness was moderate (5 nm) could Fe₃O₄ be homogeneously dispersed in both polymers, and the co-continuous structure of the corresponding scaffold (namely TPF-6) could be preserved. The TPF-6 scaffold exhibited better tensile strength of 9.89 MPa and tensile modulus of 375.28 MPa, enabling it to serve as a structural support. Besides, TPF-6 demonstrated an optimal magnetic responsive shape recovery ratio of 91.73 % and good cytocompatibility, making it a promising candidate for minimally invasive bone repair.