Formation of Hydroxyapatite Coating on Anodic Titanium Dioxide Nanotubes via an Efficient Dipping Treatment

Abstract

Hydroxyapatite (HA) depositions on metallic biomedical implants have been widely applied to generate bioactive surfaces in simulated biological environments. Meanwhile, highly ordered TiO 2 nanotubes obtained via anodization have attracted increasing interest for biomedical applications. However, the capability to grow HA coating on TiO 2 nanotubes at room temperature remains problematic. In this study, we applied a dipping treatment for biomimetic formation of an adhesive HA coating on titanium dioxide nanotubes. The coatings formed using this procedure did not require high-temperature annealing or high supersaturation of the simulated biological condition. The as-formed TiO 2 nanotubes on titanium were treated using several dip-and-dry steps, through which the TiO 2 nanotubes were filled and covered with calcium phosphate nucleation sites. The specimens readily grew HA once immersed in the original simulated biological fluid (SBF) after little more than 12 hours. The carbonated HA coating was formed with 10-lm thickness after 4 days of immersion, while only a few calcium phosphate particles were observed on annealing TiO 2 nanotubes immersed in the same solution for the same duration. Tensile testing showed that the bonding strength between HA coating and substrate was 27.2 ± 1.6 MPa. This treatment dramatically improved efficiency for promoting HA formation on anodic TiO 2 nanotubes at room temperature.

Enhancement of the capability of hydroxyapatite formation on Zr with anodic ZrO2 nanotubular arrays via an effective dipping pretreatment

“…Thus, the nanotubular diameters and layer thicknesses varied linearly with the applied potential, in agreement with earlier report. 29 The results demonstrated that the layer thickness increased with increase in the anodizing voltage, which is understandable, because an increase in anodic voltage will speed up the oxidation rate of the Zr foil, thus accelerating the formation of ZrO 2 nanotubular arrays. Figure 4(b) shows the kinetic curves for formation of nanotubular arrays under different applied voltages, showing a linear relationship between the nanotubular layer thickness and applied voltage for a given time.…”

Processing and Nanomechanical Properties of Hydroxyapatite‐Nanotube Biocomposite

“…The third type of nanotubes that has been used as reinforcement to HA is TiO 2 nanotubes [37][38][39]. The main aim of adding TiO 2 nanotubes to HA was not to increase the fracture toughness or wear resistance, unlike CNT and BNNT.…”

“…The main aim of adding TiO 2 nanotubes to HA was not to increase the fracture toughness or wear resistance, unlike CNT and BNNT. TiO 2 nanotubes, obtained as aligned nanostructures on titanium surface by anodization process, are supposed to favor deposition of HA to make the surface biocompatible [37][38][39]. Thus, HA-TiO 2 composites, reported so far, are thin coatings on titanium surface prepared by immersion in SBF or calcium and phosphate-containing bath.…”

“…Thus, HA-TiO 2 composites, reported so far, are thin coatings on titanium surface prepared by immersion in SBF or calcium and phosphate-containing bath. The main aims of such coatings are to offer more HA nucleation site on the Ti surface and to promote the bonding between the metal and biocompatible coating [39,38]. (Reproduced with permission from Elsevier, [37].)…”

“…the biocompatible coating on the metallic implant surface [37]. The addition of TiO 2 nanotubes increases the bond strength of HA coating with Ti substrate [38,39]. The formation of TiO 2 nanotubes on Ti surface is found to promote HA nucleation and protein absorption on metallic surface, which are favorable for osseointegration [37].…”