Antibacterial,Osteogenic,and Angiogenic Activities Of SrTiO₃ Nanotube Arrays Embedded With Ag₂O Nanoparticles

Due to their excellent mechanical properties,corrosion resistance and biocompatibility,biomedical titanium?Ti?and titanium alloy have been widely used for orthopedics implants.However,there are still two post-operative complications: prosthetic loosening and implants related infection.In the present study,the siliver oxide?Ag₂O?doped titania?TiO₂?nanotube?NT?arrays namely NT-Ag are fabricated by anodization of magnetron-sputtered Ti Ag coatings on the surface of pure Ti.The NT-Sr-Ag are then prepared by a hydrothermal treatment of NT-Ag in a Sr?OH?2 solution.The morphology,composition,microstructure,ion release phenomenon,as well as in vitro antibacterial,osteogenic,and angiogenic activities are investigated in details.The results are as follows:?1?In the NT-Ag,silver oxide?Ag₂O?nanoparticles?NPs?are embedded in the amorphous TiO₂ NT wall.During the hydrothermal treatment?1-5 h?,the amorphous TiO₂ in the NTs transforms to cubic SrTi O₃ gradually and the ordered nanotubular architecture is preserved.Some Ag₂ O NPs are incorporated into the structure although some of them dissolve in the solution.NT-Sr-Ag are composed of SrTiO₃ NTs embedded with Ag₂ O NPs.?2?The NT-Ag and NT-Sr-Ag samples are able to release Ag⁺ and Sr²⁺ safely and effectively for a long period of time,and the initial release is large and fast,then stabilized.10 days later,there are no significant differences in the release amount of Ag⁺ among all groups.NT-2Sr-Ag and NT-3Sr-Ag?Hydrothermal treatment for 2 and 3 h,respectively?can release larger amount of Sr²⁺ than NT-1Sr-Ag and NT-5Sr-Ag?Hydrothermal treatment for 1 and 5 h,respectively?.?3?Due to the long-term and effective Ag⁺ release,all of the NT-Sr-Ag and NT-Ag demonstrate excellent antibacterial activity.?4?No side effect is observd after Sr and Ag are introduced into the TiO₂ NTs.Introduction of the elements has no appreciable effect on adhesion,spreading and proliferation behaviors of osteoblasts.?5?Anodized samples can promote type I collagen secretion of osteoblasts when compared with that of pure Ti.Both the released Sr²⁺ and secreted vascular endothelial growth factor?VEGF?upregulate the alkaline phosphatase?ALP?activity and extracellular matrix mineralization of osteoblasts,and among them NT-2Sr-Ag and NT-3Sr-Ag with the largest Sr²⁺ release amount show the best osteogenic activity.?6?NT-Sr-Ag can also release Sr²⁺ similarly to stimulate osteoblasts to secrete the vascular endothelial growth factor?VEGF?.Furthermore,larger NO production and better in vitro angiogenic activity is observed when endothelial cells are cultured in NT-Sr-Ag conditioned media when compared with that in pure Ti and Sr-free NTs conditioned media,which is believed to be ascribed to the positive regulation of Sr²⁺ to VEGF secretion.NT-2Sr-Ag and NT-3Sr-Ag with the largest Sr²⁺ release amount also show the best angiogenic activity.In summary,NT-2Sr-Ag and NT-3Sr-Ag exhibit excellent in vitro antibacterial,osteogenic,and angiogenic activities and are promising when serve as biomedical implants coatings.