| Compared with other traditional metallic implants, pure titanium and its alloys have been widely used in clinic, due to its good mechanism properties, biocompatibility, corrosion resistance and excellent processability. However, the surface of titanium is generally bioinert and not optimal in early direct bonding with the host bone. The low bonding strength between them leads titanium implants loose or even failure. Researches indicate that the surface morphologies of materials play a significant role for the tissue healing speed and quality. Particularly, material surface with micro/nano structure can simulate the natural environment of cell growth, promoting the adsorption of proteins, cell attachment and differentiation. Developing materials with micro/nano structure surface will be a growing trend in the future. Apatite, as the main inorganic component of the bone, teeth and other hard tissues, has a good biocompatibility, biological activity and osteoconductivity. Therefore, coating calcium phosphate onto the surface of titanium with micro-and nano-structure will improve titanium biological activity, promoting the implants fixiation with bone tissue.In this experiment, firstly different micro/nano structures of titanium surfaces were fabricated by alkali-heat treatment and acid-heat treatment under hydrothermal condition. Then, the samples were characterization by scanning electron microscope (SEM), x-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), energy dispersive x-ray analysis (EDX) and contact angle measurement. Finally, the influences of micro/nano structure on osteoblasts were evaluated. Results showed that three different micro/nano structures were prepared on the surface of titanium mesh under the temperature of180℃,200℃and240℃, respectively. With the increase of temperature, the aspect ratio of nanowires on the titanium mesh increased gradually. After treatment at240℃, nano-sized ribbons with widths of approximately50-200nm and lengths of5-10μm formed on the Ti mesh surface and nano-sized ribbons on the mesh assembled hierarchically into three-dimensionally microporous surface features with typical pore diameters of5-15μm and depths of5-10μm. XRD and EDX analysis indicated that hydrated titanate formed on the mesh after the treatment. The water contact angle with titanium decreased after the alkali-heat treatment. The as-cleaned Ti disc showed a mean contact angle of90°. After alkali-heat treatment the contact angle decreased to12°. After the acid-heat treatment, aligned groove with the width of～10μm formed on the titanium mesh. Meanwhile, the microgrooves were covered with nano concaves, nano holes and nano steps. EDX、XRD and FTIR analysis indicated that no other phase but pure titanium was existence on the titanim mesh surface.Cell culture experiments proved that titanium surface with micro/nano structure had good biocompatibility and non-toxic side effects. Micro/nano structure can promote osteoblasts adhesion and proliferation, the groove structure can induct cells orientated growth.In this study, calcium phosphate coatings were deposited on the pretreated titanium surface using methods of biomineration in the supersaturated calcification solution (ACS) and hydrothermal precipitation. Results showed that a uniform layer of calcium phosphate crystals formed on the surfaces of samples immersed in ACS solution for24h after pre-calcification with dip-dry method. XRD analysis proved that calcium phosphate phase was Ca8(PO4)4(HPO4)2·5H2O. The pretreated titanium mesh was palced under hydrothermal conditions and deposited different morphologies of calcium phosphate in situ with the modulation of small molecule (H6L). Compared with deposit calcium phosphate in simulated body fluid (SBF) and ACS solutions, using hydrothermal mineration method is time-efficient and can be applied to substrates with complex geometries. Also, under hydrothermal undition, template can be used to precisely control the growth of calcium phosphate. This process has a promising prospect in preparation of calcium phosphate coating. Results found that both micro/nano structure on titanium surface and the concentration of H6L had an influence on the growth of calcium phosphate. Cell culture experiments proved that osteoblasts had a better adhesion and proliferation on the titanium surface with calcium phosphate coating.Finally, it was concluded that designing the micro/nano structure of titanium surface, controlling the coating technique and composition, and the accurate small molecule modulated orientation, better titanium-based substitues can be developed to meet the demand for bone defect restoration in clinic. |
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