Bioactive Effect of Acid-treatment on Alkali and Water-treated TiO₂ Nanotubes

Objective: NaOH and heat treatments improve the bioactivity on implant surface. Sodium removal of surface by water treatment can convert sodium titanate layer into a more bioactive state. The anatase phase affects on the formation of apatite nucleus in SBF. In this study, acid treatment was performed between alkali and water treatment to enhance bioactivity through increasing formation of anatase phase. The aim of this work is to verify that the properties and bioactivity of the alkali and water-treated TiO₂surface were improved by acid treatment. Method: Pure Ti foil was prepared for surface modification. The specimen was conducted by anodization in glycerol electrolyte, alkali treatment in 5M NaOH(60°C, 24h), acid treatment in 10 & 50mM HCl(40°C, 24h) and water treatment in ultra-pure water(40°C, 24h). Finally, specimens were thermally treated at 550°C. Surface properties were evaluated by FE-SEM, EDS and XRD. The contact angle between the SBF drop and the surface was measured. To estimate bioactivity, the specimens were soaked in SBF for 5 and 10 days. Result:  After HCl treatment, the concentration of O ions and anatase peaks was increased. After 5days of immersion in SBF, apatite-like compound accelerated on the surface of all groups. The HAp peaks and concentration of Ca and P ions is highly increased in 50mM HCl treated group. Conclusion: The hydrophilic property was demonstrated in the HCl treated groups via contact angle value, and an apatite-forming ability was also enhanced by increase of TiO₂ groups after 50mM HCl treatment. Thus, it is suggested that the HCl treatment is a favored surface modification method to improve the bioactivity of alkali and water-treated TiO₂nanotubes. This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology(2012012671 & 2012007616) and by the Korea government(MEST) (No. 2011-0028709).