Preparation Of HA/TiO₂ Coating On Titanium Surface In Situ By Micro-arc Oxidation And Loading Chitosan On It

Titanium?Ti?is the widely used implant material in clinic because of its excellent biocompatibility,corrosion resistance and mechanical processing.However,Ti is a bioinert material which can not form strong bonding with the organism and the bone tissues.In addition,Ti does not have antibacterial property,leading to the high post-operative infection rate.Therefore,it is necessary to modify the Ti surface to achieve good biological and antibacterial property.In this paper,hydroxylapatite?HA?/TiO₂ composite coatings were prepared on the Ti surface by micro-arc oxidation?MAO?,and then the HA/TiO₂ composite layers were dipped in chitosan?CS?solutions with different concentrations to load the antibacterial agent-CS by dip coating method.The influence of experimental parameters?voltage,electrolyte concentration,time and CS concentration?on surface morphology,composition,roughness and hydrophilicity were investigated.The formation rate of HA,the interface and bonding strength between HA and CS layer were explored.The dependence of CS amount loaded on HA/TiO₂ composites on CS concentration was analyzed.The morphology,composition,phase and surface functional groups of CS/HA/TiO₂ composite layer were also analyzed after degradation.The composite layers were immersed in a simulated body fluid?SBF?for a certain period to evaluate the bioactivity.The antibacterial property of the composite layers was investigated by the bacteriostatic test.Their biocompatibility was also investigated by in vitro cell culture experiments.The results are listed as follows:?1?The petal shaped HA can be prepared on Ti surface by increasing the voltage,electrolyte concentration and time of MAO,which would increase the surface roughness and hydrophilicity.?2?As the concentration of CS solution increased from 0.2g/L to 6g/L,the CS amount loaded on HA/TiO₂ composite layer would also be increased,gradually covering the morphology of the HA layer and finally forming a smooth and continuous CS layer on the Ti surface;There are both physical and chemical bonding between HA and CS;With the increase of the CS amount loaded on HA/TiO₂ composite layers,the surface roughness and hydrophilcity were also increased,and the degradation time was extended.After degradation,the original HA petals can be observed again.?3?The composite layers?HA/TiO₂?with or without CS can both induce apatite formation in simulated body fluid and have better bioactivity than pure Ti and TiO₂,but the bioactivity of HA is slightly superior to that of CS;More CS amount loaded on the composite layer,the stronger the antibacterial activity it has,and the longer antibacterial property it maintained,however,the biocompatibility is gradually reduced.