Study On Surface Modification Of Biomedical Titanium And Its Antibacterial Activity And Bioactivity

Titanium has been widely used as hard tissue implant material because of its good biocompatibility. However, titanium implant in human body is often repulsed as a foreign object due to its bioinertia. Thus, it is necessary to carry out surface modification for titanium to obtain implant with ideal performances on corrosion resistance, bioactivity and antibacterial ability. In this work, titanium surface was modified by sliver (Ag) and nitrogen (N) dual ions implantation, the depending properties of titanium, such as corrosion resistance, hardness and antibacterial ability, on Ag/N dual ion implantation sequence was investigated. To enhance the bioactivity and antibacterial activity, titanium was treated by surface modification combining chemical method (hydrothermal method) and physical method (plasma immersion ion implantation), and then its microstructure, bioactivity, antibacterial ability and cell cytotoxicity were studied. The poly (Lactic Acid)(PLA)/CaO-SiO2composite membranes were synthesized by sol-gel method, and the bioactivity and biocompatibilty of these composite membranes were examined. The results obtained are described as follows:1. Silver (Ag) and nitrogen (N) dual ions were sequentially implanted into titanium via plasma immersion ion implantation (PⅢ) technology at different implantation sequence, including PIII-Ag-N (Ag ions prior to N implantation), PIII-N-Ag (N prior to Ag ions implantation) and PIII-Ag+N (Ag/N dual ions co-implantation). Sliver and nitrogen in all modified titanium were existence of metallic sliver and titanium nitride. The Ag/N dual ions implantation sequences play an important role on the corrosion resistance and hardness of the modified samples. The results showed that the properties of samples via Ag/N dual ion co-implantation mentioned above are better than PⅢ-Ag-N and PⅢ-N-Ag, which is ascribed to the thickness of titanium nitrogen layer caused by thermal spikes effect during implantation process. The antibacterial experiments indicated Ag/N dual ions implanted titanium exhibit high antibacterial ability against Escherichia coli and Staphylococcus aureus. The cytotoxicity experiments showed the Ag/N dual ions implanted titanium can promote cell proliferation.2. Hydrogen peroxide hydrothermal method was used to modify the surface of titanium plates. The nanostructural layer consisting of Ti and O was formed on the surface of hydrothermal-treated titanium. Then, sliver was introduced into hydrothermal-treated titanium by plasma immersion ion implantation. The surface morphology of titanium as above can be remained at nano-scale level after Ag ion implantation. The corrosion resistance of hydrothermal-treated titanium before and after Ag ion implantation is better than pure titanium, while the SBF test also indicated these samples before and after sliver ion implantation exhibit well bioactivity. The Ag ion implanted samples exhibit well antibacterial ability against Escherichia coli and Staphylococcus aureus. The hydrothermal-treated titanium samples before and after Ag ion implantation are of good cytocompatibility.3. Titanium plates were hydrothermal treated in a mixture solution of hydrogen peroxide and sodium. Silver was introduced into the hydrothermal-treated titanium by plasma immersion ion implantation. The SBF test indicated the hydrothermal-treated titanium before and after sliver ion implantation exhibit good bioactivity. The Ag implanted into titanium pretreated by hydrothermal method exhibited well antibacterial ability against Escherichia coli and Staphylococcus aureus, and can promote cell proliferation except the samples pretreated by sodium hydroxide solution.4. A novel porous PLA/CaO-SiO2(nSiO2/nCao=1) composite membrane is synthesized by sol-gel method. After soaked in simulated body fluids for7days, the surfaces of the PLA/CaO-SiO2composite membranes are covered by apatite layer with orderly ring structure. With the increase of CaO-SiO2content in the composite membrane, the size of the pores on the surface of composite membrane becomes smaller, the surface zeta potentials decreases and the bioactivity become better. MTT experiments showed the composite membranes are not of cytotoxcity to MG-63cells and support cell proliferation.