Abstract: BACKGROUND: After alkali-and-heat treatment on the titanium surface, a layer of sodium titanate gel will be formed to promote the formation of bone-like apatite, thereby combining with living bone. The titanium surface will form a hydrophilic surface after ultraviolet photofunctionalization, which can increase the surface free energy, promote the adsorption of protein in body fluid, and further promote the adhesion and reaction between cells and titanium surface.  
OBJECTIVE: To explore the physical and chemical properties of alkali-and-heat treatment combined with ultraviolet photofunctionalization pure titanium surface, and its effects on adhesion, proliferation and differentiation of MC3T3-E1 cells.  
METHODS: TA2 pure titanium discs were randomly divided into three groups. The group A received acid etching treatment. The group B received acid etching + alkali-and-heat treatment. The group C received acid etching + alkali-and-heat + ultraviolet photofunctionalization treatment. The microscopic morphology, element composition, and static contact angle were characterized in the three groups of titanium discs. MC3T3-E1 cells in logarithmic growth phase were inoculated on the surface of three groups of titanium discs. CCK-8 assay was used to detect cell proliferation. Cell adhesion was observed under scanning electron microscope. After osteogenic induction and culture, the alkaline phosphatase activity, the secretion of type I collagen, and the formation of mineralized nodules were detected.
RESULTS AND CONCLUSION: (1) Under scanning electron microscope, the surface of group A was rough and honeycomb shaped, with relatively uniform pore. The surfaces of group B were distributed with loosely nano-level pores and brain-circuit like gullies. The gullies and pores were cross-linked with each other. The surfaces of group C also had nanoporous network structure, and the distribution and size of gullies and pores were not significantly different from that of group B. (2) C, O, Ti, and P elements were both found on the surfaces of the three groups, and Ca element was also detected on the surfaces of groups B and C, but Ca element was scarcely found on the surface of group A. The static contact angle of group A was the smallest, while that of group C was the largest. (3) Scanning electron microscope showed that there were more cells on the surface of the titanium plates in each group at 24 hours after injection. The cells in groups A and B were long fusiform, triangular or flat. The cells in group C were larger in diameter and had several pseudopods, and the flat polygons were spread into a thin layer on the surface of the titanium plates, interconnected, and unable to distinguish cell boundaries. (4) The cell proliferation on the surface of titanium plates in group C was faster than that in groups A and B, and the alkaline phosphatase activity, type I collagen secretion and the number of mineralized nodules in group C were higher than those in groups A and B. (5) The results showed that alkali-and-heat treatment combined with ultraviolet photofunctionalization could effectively improve the physical and chemical properties of pure titanium surface and promote the biological activity of osteoblasts.

Key words: implant, titanium disc, ultraviolet, photofunctionalization, alkali-and-heat treatment, osteoblast, surface treatment