Microscopic observations of osteoblast growth on micro-arc oxidized β titanium

摘要

Titanium alloys are widely used in orthopedic and dental implants, owing to their excellent physical properties and biocompatibility. By using the micro-arc oxidation (MAO), we generated anatase-rich (A-TiO_2) and rutile-rich (R-TiO_2) titanium dioxide coatings, individually on p-Ti alloy, in which the latter achieved an enhanced in vitro and in vivo performance. Thoroughly elucidating how the osteoblasts interact with TiO_2 coatings is of worthwhile interest. This study adopts the focused ion beam (FIB) to section off the TiO_2 coated samples for further scanning electron microscope (SEM) and transmission electron microscope (TEM) observation. The detailed crystal structures of the TiO_2 coated specimens are also characterized. Experimental results indicate osteoblasts adhered more tenaciously and grew conformably with more lamellipodia extent on the R-TiO_2 specimen than on the A-TiO_2 and raw β-Ti specimens. FIB/SEM cross-sectional images of the cell/TiO_2 interface revealed micro gaps between the cell membrane and contact surface of A-TiO_2 specimen, while it was not found on the R-TiO_2 specimen. Additionally, the number of adhered and proliferated cells on the R-TiO_2 specimen was visually greater than the others. Closely examining EDS line scans and elemental mappings of the FIB/TEM cross-sectional images of the cell/TiO_2 interface reveals both the cell body and interior space of the TiO_2 coating contain nitrogen and sulfur (the biological elements in cell). This finding supports the assumption that osteoblast can grow into the porous structure of TiO_2 coatings and demonstrating that the R-TiO_2 coating formed by MAO serves the best for β-Ti alloys as orthopedic and dental implants.