title: Enhancement of the capability of hydroxyapatite formation on Zr with anodic ZrO₂ nanotubular arrays via an effective dipping pretreatment.
abstract: Hydroxyapatite (HA) depositions on metallic biomedical implants are widely applied to generate bioactive surfaces in simulated biological environments. Highly ordered anodic ZrO₂ nanotubes have attracted increasing interest for biomedical applications. However, previous reports showed that at least 14-28 days were required to obtain HA coating on ZrO₂ nanotubular arrays under biomimetic condition, thus capability to grow HA coating on ZrO ₂nanotubular at room temperature needs to be enhanced. In the present work, we demonstrate that ZrO₂ nanotubular arrays are suitable for an effective dipping treatment to induce more rapid HA coating. A series of ZrO₂ nanotubular arrays having different dimensions were fabricated in fluoride containing electrolyte. Then, we used a dipping treatment for biomimetic formation of an adhesive HA coating on the nanotubular arrays. The coatings formed rapidly using this procedure under biomimetic conditions and did not require a high-temperature annealing process. The as-formed ZrO₂ nanotubular arrays were treated using several dip-and-dry steps, through which the nanotubular arrays were filled and covered with calcium phosphate (CaP) nucleation sites. The specimens readily grew HA once immersed in the simulated biological fluid after 2 days immersion. The carbonated HA coating had several micron thickness after 8 days of immersion while only a thin layer of CaP were observed on annealed ZrO₂ nanotubes immersed in the same solution for the same duration. Tensile testing showed that bonding strength between HA coating and substrate was 21.6 ± 1.6 MPa. This treatment dramatically improves efficiency for promoting HA formation on anodic ZrO₂ nanotubes at room temperature.
authors.affiliation: Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, Canada T6G 2V4.
authors.forename: Lu-Ning
authors.initials: LN
authors.lastname: Wang
authors.forename: Alissa
authors.initials: A
authors.lastname: Adams
authors.forename: Jing-Li
authors.initials: JL
authors.lastname: Luo
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D017886:Durapatite / Q000737:chemistry*; D004566:Electrodes; D004573:Electrolytes / Q000737:chemistry; D005459:Fluorides / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008855:Microscopy, Electron, Scanning / Q000379:methods; D008956:Models, Chemical; D036103:Nanotechnology / Q000379:methods*; D043942:Nanotubes / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013499:Surface Properties; D014961:X-Ray Diffraction; D015040:Zirconium / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D004573:Electrolytes; D007477:Ions; D017886:Durapatite; D015040:Zirconium; D005459:Fluorides; C028541:zirconium oxide; D002118:Calcium