Abstract

Titanium (Ti) and its alloys have been widely used to treat weight-bearing bone defects. However, high stress shielding, weak osteogenic activity, and insufficient vascularization remain challenges for the clinical application of titanium-based implants. In this study, Sr 2+ -doped hydroxyapatite (HA) composite coatings with good biocompatibility and pro-angiogenic properties were fabricated on the surface of 3D-printed porous titanium alloy via biomimetic mineralization using polydopamine (PDA) as a binder. The crystal structure, phase composition, micromorphology, and chemical bonding of the composite scaffolds were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Sr 2+ doping led to a reduction in crystallinity. When the doping level was less than 15%, the scaffold exhibited a stable HA release rate. Water contact angle measurements and atomic force microscopy (AFM) revealed that the scaffold surface possessed high roughness and enhanced hydrophilicity. CCK-8 assays and cell live/dead staining demonstrated the excellent biocompatibility of the scaffold. Furthermore, alizarin red staining, scratch tests, and angiogenesis assays confirmed that Sr 2+ incorporation significantly improved the osteogenic and angiogenic capabilities of the composite scaffold. These in vitro findings suggest that the PDA-assisted Sr-HA coating, especially at a 15 mol% doping level, can effectively modify the surface of 3D-printed porous titanium to improve its bioactivity. This study provides a methodological reference and preliminary cellular-level evidence for developing multifunctional titanium-based bone implants, though further in vivo validation is required to assess its full clinical potential.