Bioactive and antibacterial polycaprolactone-coated TiO₂/hydroxyapatite nanocomposites doped with silver for bone implant applications

Titanium-based implant materials are widely used in clinical practice due to their favorable mechanical properties and biocompatibility; however, their surfaces remain susceptible to bacterial adhesion and biofilm formation, which are leading causes of implant failure. To address this limitation, the present study reports the development of a multifunctional antibacterial and bioactive TiO₂/HAp/Ag nanocomposite for bone implant applications. Titanium dioxide was partially substituted with 5 wt% hydroxyapatite (HAp) produced from natural bovine bone and doped with 0.005 M silver nitrate to impart antimicrobial functionality. The composite surface was subsequently coated with polycaprolactone (PCL) to regulate Ag⁺ release and reduce cytotoxicity. Structural property analyses confirmed the formation of nanocrystalline hydroxyapatite with a Ca/P molar ratio of 1.64, nearly matching stoichiometric bone apatite. In vitro bioactivity analysis in simulated body fluid (SBF) at 36°C showed quick formation of a calcium-phosphate-rich apatite layer within 10 days, suggesting strong osteointegration potential. Antibacterial assays exhibited notable activity against Staphylococcus aureus and Escherichia coli, with biofilm inhibition exceeding 94%, while hemolysis analyses verified remarkable blood compatibility. Mechanical characterization of the ceramic substrate showed a Vickers hardness of 2.82 GPa, Brazilian tensile strength of 17.87 MPa, and compressive strength of 89.34 MPa, placing the material within the upper range of cancellous bone and close to the lower bound of cortical bone. Overall, the results demonstrate that the designed TiO₂/HAp/Ag/PCL nanocomposite combines mechanical suitability, bioactivity, antibacterial protection, and hemocompatibility, making it a promising candidate for infection-resistant bone implant applications.