Abstract: BACKGROUND: Nanostructure modification of pure titanium surface is a hot research field of titanium implant surface treatment. 
OBJECTIVE: To evaluate the effect of nano-modified titanium surface treated with alkali heat treatment on early adhesion and growth of osteoblasts.
METHODS: Four-grade pure titanium sheets with a diameter of 15 mm and a thickness of 1.5 mm were taken and processed in three groups: the smooth treatment group was polished step by step with 250 mesh, 800 mesh, and 1 500 mesh silicon carbide sandpaper. In the sandblasting group, the smoothed titanium sheet was sandblasted with 100 μm Al2O3 particles at 0.45 MPa pressure, and then the acid etching was carried out. In the alkali heat treatment group, the smoothed titanium sheet was placed in the reactor, immersed in 10 mol/L NaOH solution, and heated in the oven at 100 °C for 12 hours. The surface morphology, roughness, and hydrophilicity of three groups of titanium sheets were measured. MG63 osteoblasts were inoculated on the surface of three groups of titanium tablets, and the adhesion of the cells was observed by immunofluorescence staining. 
RESULTS AND CONCLUSION: (1) Scanning electron microscopy showed that the surface of titanium sheets in the smooth treatment group had uniform scratches; the surface of titanium sheets in the sandblasting group was uneven, and the surface of titanium sheets in the alkali heat treatment group had uniform nanoscale three-dimensional pore morphology. The roughness value of the titanium sheets in sandblasting and alkali heat treatment groups was higher than that in the smooth treatment group (P < 0.05), and the water contact angle was lower than that in the smooth treatment group (P < 0.05). (2) Immunofluorescence staining after 3 and 6 hours of inoculation of MG63 cells showed that the number of adhesion cells on the surface of the titanium sheet in the sandblasting group and alkali heat treatment group was higher than that in the smooth treatment group (P < 0.05). Immunofluorescence staining 12 hours after inoculation showed that compared with the smooth treatment group, the actin skeleton of cells on the surface of titanium sheets in the sandblasting group and alkali heat treatment group was more extended, and most cells extended stronger pseudopodia, which was conducive to subsequent intercellular signal transduction and intercellular interaction. (3) The results showed that the nanostructures with certain biological activity could be prepared on the surface of a titanium sheet by alkali heat treatment, which was conducive to the early adhesion of osteoblasts.

Key words: titanium surface, nanostructure, alkali heat treatment, sandblasting acid etching, osteoblast, biomaterial