Development of sol–gel derived fluoridated hydroxyapatite/CaTiO3 composite coating on titanium implant

The difficulties in regulating the degradation of hydroxyapatite (HA)-coated titanium implants necessitate the development of innovative solutions to ensure their biological safety and long-term durability. This study aims to investigate the combined effects of CaTiO₃ incorporation and controlled fluoride substitution on HA-based composite coatings deposited onto Ti6Al4V substrates via sol–gel, with fluoridation levels systematically varied to assess their structural, mechanical, chemical, and biological performance. The phase composition, chemical bonding, elemental composition, and coating morphology were characterized by XRD, FTIR, XPS, and SEM, respectively. The composite coatings’ modulus of elasticity and hardness were investigated using a nanoindentation test, which has shown that CaTiO 3 and fluoride ions considerably improve the mechanical properties of the HA layers. Moreover, the adhesion strength of the composite coatings has shown significant improvement with increasing fluoridation degree. The investigation of the dissolution behavior showed that all fluoridated apatite coatings have a lower degradation rate, which indicates the possibility of tailoring the solubility of apatite structures in phosphate-buffered saline (PBS) as fluoride is incorporated. The potentiodynamic polarization test demonstrated that composite coatings on titanium alloy exhibit a lower corrosion rate than pure HA-coated samples. The fluoride-doped coatings exhibited antibacterial efficacy against S. aureus and E. coli bacteria. In vitro cellular responses evaluated with human osteosarcoma MG-63 cells revealed stimulated cell proliferation and differentiation activities as fluoride was incorporated. This study demonstrates that fluoridated apatite/CaTiO 3 composite coatings have several advantages over pure hydroxyapatite coatings in terms of mechanical properties, chemical stability, and cellular responses.