Synergistic enhancement of gradient structure and hydroxyapatite crystals on the biomechanical compatibility of biomimetic 3D printed porous scaffold

The biomimetic porous scaffold with excellent biomechanical compatibility was successfully created using 3D printing, micro arc oxidation (MAO) and microwave hydrothermal treatment (MHT). Initially, the scaffold's elastic modulus and compression strength could be adjusted by altering the pore size and type, resulting in a porous scaffold with a low modulus and high strength. The deformation process displaced a layer by layer fracture at a 45° angle. Subsequently, a bioactive coating containing uniform and abundant of hydroxyapatite (HA) crystals was applied to the scaffold's surface through MAO and MHT. This coating did not significantly impact on the elastic modulus and compression strength. The difference in thickness between the inner and outer coating on the porous scaffold was primarily due to the variations in the micro arc discharge capability within the pore structure. Compared to MHT-treated STS and DoST, the MHT-treated DiST porous scaffold exhibited superior apatite-inducing ability, likely due to the abundant HA crystals formation on the surface. After a 6-week in vivo animal experiment, it was observed that the MHT-treated DiST porous scaffold demonstrated enhanced osseointegration ability, attributed to the high bioactivity of HA crystals and good mechanical compatibility. The research findings suggested a transformation in the bone in-growth pattern of the porous scaffold from distant osteogenesis to contact osteogenesis. Therefore, the biomimetic multi-scale porous scaffold with outstanding biomechanical compatibility could be a promising candidate for repairing bone defects.