Filling TiO_2 Nanotubes with Biological Apatite by Alternative Loop Immersion Method

A vertically aligned TiO_2 nanotube array was fabricated on the surface of titanium substrate in fluoridecontaining electrolyes by anodization.Alternative Loop Immersion Method(ALIM) was investigated to fill TiO_2 nanotubes with the biological apatite in the saturated solution of Ca(OH)_2 and 0.02 mol/L(NH_4)_2HPO_4.In this way,the structure of the apatite-coating on the Ti substrate was changed for solving the problem of coating shedding well.And the amount of synthetic apatite formed by ALIM was quantified according to key tube properties such as the tube diameter, the layer thickness,the crystal structure(amorphous or anatase),etc.The effect of filling biological apatite of TiO_2 nanotubes fabricated in glycerol-based electrolyte at 60V is the best.And the rate of inducing biological apatite on amorphous TiO_2 nanotubes with the treatment of ALIM is better than that of anatase TiO_2 nanotubes.Mineralization in vitro experiments indicates that TiO_2 nanotubes after ALIM treatment promote natural apatite formation significantly in a simulated body fluid(SBF).Such TiO_2 nanotube arrays with ALIM treatment,are useful as a well-adhered bioactive surface layer on Ti implant metals for orthopaedic and dental implants.