Fabrication of large diameter TiO₂ nanotube for bone morphogenetic protein-2 delivery

A localised and release-controlled carrier is essential to enhance the effectiveness of bone morphogenetic protein in bone regeneration and repair. In this work, TiO₂ nanotubes with diameter larger than 350 nm were successfully fabricated for the first time by electrochemical method using diethylene glycol electrolyte. The diameter of the nanotubes reaches 550 nm and 680 nm at 90 V and 100 V, respectively. Their influences for bone morphogenetic protein-2 (BMP-2) delivery were investigated. In the study of protein release, fabricated TiO₂ nanotubes have shown superhydrophilic properties that induce tight interaction with BMP-2. The release profile of the TiO₂ nanotubes demonstrated a larger retention of protein, a more significant suppression of the initial burst and a better retardation of the release rate. Elution profile was also found to be dependent greatly on the density and the diameter of the nanotubes. Results have shown that the initial burst was larger for nanotubes with lower density and more proteins were released from nanotubes with larger diameter for the whole elution process.