Topological optimization synergized with a high-activity nano-hydroxyapatite coating to enhance bone regeneration in porous titanium alloy scaffold

Surface bioinertness-induced fibrosis at and within 3D-printed porous titanium implants critically impairs their repair efficacy. Surface bioactive and even-distributed coating construction represents an ideal strategy to address this challenge. Herein, a porous titanium alloy scaffold with an appropriate fluid dynamics microenvironment was prepared using computational fluid dynamics (CFD) simulations and selective laser melting (SLM) technology. Subsequently, a uniform nano-hydroxyapatite (nHA) coating with about 30 μm thickness and good bonding strength was fabricated on the chemically pretreated scaffold via surface engineering and gradient liquid-phase impregnation. The nHA coating significantly promoted the adhesion, proliferation, and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) on the scaffold. In a beagle intramuscular model, the rhombic dodecahedron (RD) lattice exhibited superior osteoinduction to diamond (D) and hexagonal close-packed (HCP) lattices, owing to deeper fluid penetration and uniform shear stress. Furthermore, in a rabbit femoral condyle critical-sized defect model, the topology-optimized, surface-modified titanium alloy scaffold exhibited superior interfacial osseointegration and internal bone regeneration. This study not only offers a new approach to addressing current challenges in clinical titanium implant applications but also provides novel insights into the design of 3D-printed functionalized implants.