Surface Modification Of Titanium For Biocompatibility Enhancement

Titanium is frequently used as bone replacement materials because of its excellent mechanical properties, corrosion resistance and low elastic modulus comparing with other metal biomaterials. However, being bio-inert, following implantation it takes several months to form a direct structural and functional connection with bone tissue. Surface modification is an effective way to improve the biocompatibility of titanium.In the first part of this study, two electrochemical methods, anodic oxidation (AO) and micro-arc oxidation (MAO), were used to modify the surface of titanium. The pretreatment method and optimal parameters of anodic oxidation treatment have been systematically investigated in this study. Our results show that the chemical polishing solution (HF:HNO3=1:1, v:v) can remove the original oxide film on the surface quickly and evenly. During the anodic oxidation treatment, the ideal specimens were obtained when titanium plates immersed in the reaction buffer, containing H3PO4 (0.5mol / L) and NaF (0.12mol / L), and were applied a fixed voltage of 10V for 20 minutes. Orderly arranged nanotubes with around 70 nm diameter have been observed at the surface of oxidated samples prepared under previous described optimal conditions. For micro-arc oxidation treatment , the optimal electrolyte contains 0.1mol/L calcium acetate (Ca(CH3COO)2) and 0.1mol/L sodium glycerophosphate (Na2C3H5(OH)2PO4). Samples were oxidated with the optimal current density, 15A/dm2, for 4 minutes to form a Ca and P containing coating. The SEM analysis displays that pores about 7μm diameter has been generated on the surface of titanium plate after this treatment. The western blotting analysis demonstrates that the titanium after anodic oxidation and micro-arc oxidation treatment promotes the fibronectin expression in MG-63 cells, resulting in enhanced cell adhesion and cell proliferation.In the second part, we modified the titanium surface by applying a biodegradable drug delivery coating, consisting of poly(3-hydroxyburyrate-co-3-hydroxyvalerate) (PHBV) and icariin. The coating was prepared by evaporating chloroform solution containing PHBV and icariin on the titanium under vacuum condition. Numerous closely distributed nanotubes of anodic oxidation treated titanium plates facilitate adhesion of the icariin/PHBV coating. The icariin/PHBV coating with around 70μm thickness tightly attaches to the surface of anodic oxidation treated titanium. The icariin/PHBV coated titanium plates significantly enhance the proliferation of MG-63 cells comparing with the PHBV coated and anodic oxidized ones. Increased icariin containing of the coating displays an elevated influence to cell proliferation. Our data demonstrate that icariin gradually releases from the coating to cells mainly through phospholipid-based cellular membrane instead of the culture medium.The overall results suggest that both of the surface modification methods can be used to enhance the biocompatibility of titanium.