Preparation And Bioactivity Of Tio₂ Hollow Spheres

As implant materials, titanium and its alloys have been widely used in human hard tissue replacement and repair due to their higher mechanical properties and excellent biocompatibility. Titanium metal without bioactivity must be surface modified to attain bioactivity, that is, its surface is covered with titania (TiO₂) thin film so as to achieve activation. Mainly the TiO₂ layer is obtained by oxidizing of titanium substrate itself. However, most of the preparation process contains heat treatment, which restricts the choice of substrate material and the bioactivity of TiO₂ films. The preparation of crystalline TiO₂ thin film at low temperature, without subsequent high temperature treatment, has a positive effect on maintaining the bioactivity of the film.In this thesis, TiO₂ thin films with the surface structure of hollow spheres were successfully prepared on Ti substrate by hydrolysis - gel method and layer-by-layer self-assembly technology. After ultraviolet (UV) irradiation in different parameters, induced hydroxyapatite deposition capacity of thin film was evaluated through simulated body fluid (SBF) immersion. The phase composition, surface morphology appearance, functional groups of modified films were characterized and analyzed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR) and other related tests. The osteoblasts culture on its surface was carried out so as to evaluate biocompatibility and safety of TiO₂ thin films. The research results as follow:1. TiO₂/PS composite microspheres with high uniformity and good dispersibility were successfully prepared on Ti substrate at 90°C in the pH 1.02 treatment solutions. TiO₂ hollow spheres with complete surface structure were attained by the two methods-calcination and dissolution. SBF immersion results show that the bioactivity of the dissolved group was better than the calcined group.2. UV radiation can increase the quantity of active Ti-OH groups on TiO₂ hollow spheres surface and enhance the ability to induce hydroxyapatite deposition of TiO₂ hollow spheres. With prolonged irradiation, the bioactivity of films improves. Irradiation media has a certain extent effect on the bioactivity of TiO₂ thin films. 3. Through simulated body fluid immersion and cell culture,TiO₂ thin films show excellent characteristics of hydroxyapatite deposition and in vitro cell compatibility, that is, TiO₂ hollow spheres thin films have good bioactivity. Meanwhile, the thin films don't have obvious damage on the osteoblast, which have a good biosynthesis capacity. All these show the biosafety of TiO₂ thin films is good.