F-Doped Micropore/Nanorod Hierarchically Patterned Coatings for Improving Antibacterial and Osteogenic Activities of Bone Implants in Bacteria-Infected Cases

Advanced titanium (Ti) based bone implants with antibacterial and osteogenic activities are extremely needed in clinics. Herein, biomimetic hierarchical micropore/nanorod patterned coatings (MNRs) on Ti were developed, in which the nanorods revealed a fixed interrod spacing of about 70 nm and consisted of fluorine (F) incorporated Ca₉Sr₁(PO₄)₆(OH)₂ (Sr₁-HA, strontium containing hydroxyapatite) with the fixed Sr but different F content. The incorporation of F was determined by XRD, FTTR, and TEM, revealing the substitution of OH^- in Sr₁-HA to F^-. The topography, surface roughness, and hydrophilic nature of MNRs were not apparently affected by the incorporation of F. The antibacterial and osteogenic activities of MNRs were assessed in vitro and in a bacterial-infected rabbit model. Both the in vitro and in vivo results showed that F-free and ∼1 wt % F doped MNR significantly promoted osteogenic activity compared to that of Ti but showed a lack of antibacterial activity. The incorporation of a higher dose of F led to the significantly improved antibacterial and osteogenic activities, and the effects were related to the incorporated F dose. In total, compared to F-free, ∼1, ∼2, and ∼7 wt % F doped MNRs, ∼5 wt % F doped MNR significantly enhanced antibacterial and osteogenic activities, especially new bone formation and osseointegration in the bacteria-infected case, showing a high potential as the next generation of advanced bone implant.