Hydroxyapatite thin film coatings on nanotube-formed Ti-35Nb-10Zr alloys after femtosecond laser texturing

Abstract

To achieve excellent biocompatibility of metal-based implants, hydroxyapatite thin film coatings on nanotube-formed Ti-35Nb-10Zr alloys after femtosecond laser texturing have been investigated. Three groups of samples were prepared: (1) microtextured surfaces using femtosecond (FS) laser, (2) nanotube surfaces formed by anodization, and (3) hydroxyapatite coatings vapor-deposited by a physical electron beam method on the Ti-35Nb-10Zr ternary alloy. The surface morphology of the Ti-35Nb-10Zr alloys was examined by x-ray diffractometry, field-emission scanning electron microscopy, and energy-dispersive x-ray spectroscopy. To investigate ion release, potentiodynamic polarization testing was carried out in 0.9%NaCl solution, and wettability tests and MG 63 osteoblast-like cell culture studies were performed on the surfaces of the three groups to evaluate contact angle and cell growth morphology, respectively. The Ti-35Nb-10Zr alloys exhibited the equiaxed beta phase structure. The FS laser-treated Ti-35Nb-10Zr alloys showed circular traces with diameters of 28 +/- 1.5 mu m and hole separations of 50 mu m, and the nanotubes formed on the surfaces had diameters of 180 +/- 15 nm and compositions consistent with TiO2, Nb2O5, and ZrO2. The nanotube structure showed anatase, rutile and beta-titanium diffraction peaks, whereas the HA-coated surface on the nanotubes showed hydroxyapatite, anatase and rutile peaks. The HA coatings displayed the desired role of decreasing the metal ion release with a lower current density value, and the nanotubes and FS laser-treated surface showed wider passive regions compared to other surfaces. The HA-coated surface on the nanotubes after FS laser texturing showed the lowest contact angle compared with the other surfaces. From FE-SEM observations, cell attachment and spreading of MG 63 cells showed significantly higher tendency for surfaces covered by HA coating and nanotubes. (c) 2012 Elsevier B.V. All rights reserved.