Fabrication and characterization of electrophoretically deposited chitosan-hydroxyapatite composite coatings on anodic titanium dioxide layers

Highlights: • Nanoporous anodic titanium dioxide (ATO) (anatase) layers synthesized by anodization and annealing. • Chitosan-hydroxyapatite composite coatings formed by electrophoretic deposition (EPD). • EPD parameters (voltage, time, and concentration of hydroxyapatite) optimized. • Model describing the relationship between the mass of coating and EPD parameters proposed. -- Abstract: Anodic nanoporous titanium dioxide (ATO) layers were synthesized via a three-step anodization process in a solution based on ethylene glycol containing fluoride ions and water. The as-prepared samples were annealed at 400 °C in order to transform amorphous oxide into the anatase phase. The anatase samples were coated with a chitosan-hydroxyapatite composite by using electrophoretic deposition (EPD) technique. A design of experiments (DoE) approach with Taguchi methodology was used in order to optimize the EPD parameters (voltage, time, and concentration of hydroxyapatite). A model describing the relationship between the mass of chitosan-hydroxyapatite composite coating and EPD parameters was proposed. The suggested model allows to estimate the mass (yield) of the coating based on the applied voltage, deposition time, and concentration of hydroxyapatite. It was shown that the concentration of hydroxyapatite in the suspension has the most significant impact on the morphology of the deposited coating. The coatings were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), contact angle and surface roughness measurements. The presence of chitosan-hydroxyapatite composite coatings increased the surface roughness of coated samples compared to the bare ATO layers. The morphology, compositional analysis, and crystalline phases of the EPD coatings confirmed that the anodic TiO₂ samples were successfully coated with a chitosan-hydroxyapatite composite to achieve a more suitable bone-contacting surface.