A Novel Strategy for Achieving Immunomodulation and Osseointegration of Titanium Alloys: Boron-Doped Porous Coating...

Durable performance of metallic implants depends largely on robust osseointegration and a balanced immune microenvironment at the bone-implant interface. Modulating macrophage polarization and osteoblast responses through surface topography and chemistry has emerged as an effective strategy for improving titanium alloy implants. In this study, boron-containing hierarchical porous ceramic coatings were fabricated on the low-modulus Ti-19Zr-10Nb-1Fe alloy using a one-step micro-arc oxidation process. The pore topography, surface roughness, wettability, and boron release kinetics were regulated by adjusting the applied voltage. Among the tested coatings, the M300V exhibited stronger coating adhesion and improved corrosion resistance. In vitro, the M300V coating promoted osteoblast proliferation and differentiation and induced macrophage polarization toward an M2-like phenotype. Macrophage-conditioned medium from the M300V group further enhanced osteoblast differentiation, indicating a beneficial immunomodulatory effect on osteogenesis. These responses were accompanied by increased expression of osteogenesis-related markers, including RUNX2, COL1, and OCN. In a rat femoral condyle model, the M300V coating reduced early inflammatory responses, suppressed osteoclast activity, and improved osseointegration. These findings suggest that the improved biological performance of the M300V coating may result from the combined effects of favorable boron release kinetics and hierarchical porous microstructures, providing a promising surface modification strategy for bone-interfacing titanium alloy implants.