Combined antibacterial and osteogenic in situ effects of a bifunctional titanium alloy with nanoscale hydroxyapatite coating.

To resolve the problems of bacterial infections and the low efficiency of osteogenesis of implanted titanium alloys in clinical dental and bone therapy, we developed a bifunctional titanium alloy (Ti) with a nano-hydroxyapatite (HA) coating (HBD + BMP/HA-Ti), which enables the sustained release of the natural antimicrobial peptide human β-defensin 3 (HBD-3) and bone morphogenetic protein-2 (BMP-2). Due to the poriferous nano-sized structure of the HA coating with a 20-30 μm thickness, the HBD + BMP/HA-Ti material had a high encapsulation efficiency (>74%) and exhibited synchronized slow release of HBD-3 and BMP-2. In an antibacterial test, HBD + BMP/HA-Ti prevented the growth of bacteria in an inoculated medium, and its surface remained free from viable bacteria after a continuous incubation with Gram-negative and Gram-positive strains for 7 days. Furthermore, good adhesion, proliferation and osteogenic differentiation of hBMSCs in contact with HBD + BMP/HA-Ti were achieved in 7 days. Therefore, the bifunctional titanium alloy HBD + BMP/HA-Ti has a great potential for eventual applications in the protection of implants against bacteria in the orthopaedic and dental clinic.