Diameter-sensitive biocompatibility of anodic TiO2 nanotubes treated with supercritical CO2 fluid

Ming-Ying Lan,Jeng-Kuei Chang,Sheng-Wei Lee,Her-Hsiung Huang,Chia-Pei Liu

doi:10.1186/1556-276x-8-150

Abstract

This work reports on the diameter-sensitive biocompatibility of anodic TiO2 nanotubes with different nanotube diameters grown by a self-ordering process and subsequently treated with supercritical CO2 (ScCO2) fluid. We find that highly hydrophilic as-grown TiO2 nanotubes become hydrophobic after the ScCO2 treatment but can effectively recover their surface wettability under UV light irradiation as a result of photo-oxidation of C-H functional groups formed on the nanotube surface. It is demonstrated that human fibroblast cells show more obvious diameter-specific behavior on the ScCO2-treated TiO2 nanotubes than on the as-grown ones in the range of diameters of 15 to 100 nm. This result can be attributed to the removal of disordered Ti(OH)4 precipitates from the nanotube surface by the ScCO2 fluid, thus resulting in purer nanotube topography and stronger diameter dependence of cell activity. Furthermore, for the smallest diameter of 15 nm, ScCO2-treated TiO2 nanotubes reveal higher biocompatibility than the as-grown sample.

Highlights

Titanium (Ti) and its alloys have been widely used for dental and orthopedic implants because of their favorable mechanical properties, superior corrosion resistance, and good biocompatibility [1,2,3]
In conclusion, this study investigates the diametersensitive biocompatibility of supercritical CO2 (ScCO2)-treated TiO2 nanotubes of different diameters prepared by electrochemical anodization
We find that ScCO2-treated TiO2 nanotubes can effectively recover their surface wettability under UV light irradiation as a result of photo-oxidation of C-H functional groups formed on the surface

Summary

Introduction

Titanium (Ti) and its alloys have been widely used for dental and orthopedic implants because of their favorable mechanical properties, superior corrosion resistance, and good biocompatibility [1,2,3]. When exposed to the atmosphere, the Ti metal spontaneously forms a thin, dense, and protective oxide layer (mainly TiO2, approximately 10 nm thick) on its surface, which acts like a ceramic with superior biocompatibility. When the Ti implant is inserted into the human body, the surrounding tissues directly contact the TiO2 layer on the implant surface. The surface characteristics of the TiO2 layer determine the biocompatibility of Ti-based implants. Earlier studies primarily investigated the influence of surface topography of implants on cell behaviors at the micrometer scale [4,5,6]. The interaction of nanometric scale surface topography, especially in the sub-100-nm region, with cells has been recognized as an increasingly important factor for tissue acceptance and cell survival [7,8,9].

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