Surface modification of nanotubular anodized Ti–7.5Mo alloy using NaOH treatment for biomedical application

Abstract

In this study, NaOH/heat treated nanotube layers formed on anodized Ti–7.5Mo were subjected to a variety of alkali treatment conditions to obtain improved apatite forming ability. The as-fabricated nanotubes formed on Ti–7.5Mo by anodization at 10 V in NH4F/NaCl electrolyte were amorphous. After 3 h of heat treatment at 450°C, these nanotubes crystallized into the anatase phase. The heat-treated nanotube arrays were mainly composed of TiO2, MoO2, MoO3, and Mo2O5. However, the intensity of the Mo 3d spectra in the Ti–7.5Mo surface was indiscernible after 5 M of NaOH treatment; the peak assigned to Na was detected after the alkali treatment. Anodized Ti–7.5Mo is more bioactive and has a nanoscale porous network structure when it is chemically treated with a NaOH solution. These properties are absent on anodized surfaces that are not NaOH treated. After the 5 M NaOH-treated Ti–7.5Mo specimen was soaked in simulated body fluid for 6 h or less, nano-sized apatite particles completely covered the entire porous network surface. After immersion in simulated body fluid for 14 days, the thickness of the Ca-P layer on the anodized and either 0.5 or 5 M NaOH-treated Ti–7.5Mo surface was about 418 nm and 439 nm, respectively. However, the thickness of the Ca-P layer on the anodized Ti–7.5Mo surface that was not subjected to alkali-treatment was approximately 415 nm. The preliminary in vitro cell culturing results showed that the anodized and NaOH- and heat-treated Ti–7.5Mo alloys not only had good biocompatibility, but also supported cell adhesion.