Preparation and antibacterial properties of La-doped TiO₂ films on 3Y-TZP ceramic surface

To prepare the La-doped TiO₂ film on the surface of 3Y-TZP ceramics in order to observe its antibacterial properties, providing an experimental basis for the application of antibacterial zirconia ceramics in the clinic.

A cylindrical 3Y-TZP specimen with a diameter of 20 mm and a height of 3 mm was prepared. The solgel method was used to prepare 1% lanthanum (La)-doped TiO₂ sol, and the La-TiO₂ film-3Y-TZP ceramic was prepared by dip coating on the surface of 3Y-TZP. The TiO₂ thin film-3Y-TZP ceramic was prepared by adding no lanthanum nitrate solution in the same way. The surface morphology of 3Y-TZP ceramic specimens (3Y-TZP group), TiO₂ thin film-3Y-TZP ceramic specimens (TiO₂ film group), and La-TiO₂ thin film-3Y-TZP ceramic specimens (La-TiO₂ film group) was observed by scanning electron microscopy, and photocatalysis, antibacterial and cytotoxicity experiments were carried out. For the photocatalytic experiment, four specimens were randomly selected from the La-TiO₂ film group and TiO₂ film group to observe the degradation rate of methylene blue at different time points under sunlight. In the antimicrobial experiment, five specimens were randomly selected from the La-TiO₂ film group, TiO₂ film group and 3Y-TZP group. The antimicrobial activity of each group was tested using the bacteriostatic circle method, and the bacteriostatic distance of each group was compared. In the cytotoxicity experiment, three samples were randomly selected from the LaTiO₂ film group, TiO₂ film group and 3Y-TZP group (negative control group), and the extracts were prepared. Here, 0.064% phenol solution were served as the positive control group. Morphological observation of L- 929 cells in four groups was performed after 3 d of culture. Cell viability and relative cell proliferation were measured by MTT assay.

La-TiO₂ films with uniform distribution can be prepared on a 3Y-TZP surface by the dipping-drawing method. Photocatalytic experiments showed that the degradation rate of methylene blue in the La-TiO₂ film group was (41.2 ± 1.5)% in daylight for 2 hours, which was higher than that in TiO₂ film group (36.5 ± 2.4)%. A significant difference was noted between the two groups (t＝3.321, P＝0.016). The antimicrobial experiment showed that the antimicrobial distance of La-TiO₂ group was (0.34 ± 0.08) mm, which was larger than that of TiO₂ group (0.12 ± 0.02) mm. No obvious antimicrobial circle was noted in 3Y-TZP group, and the antimicrobial distance of the La-TiO₂ film group was larger than that of TiO₂ film group (F＝63.798, P < 0.001). Cytotoxicity test showed that the relative proliferation rate of cells in LaTiO₂ film group was (89.5 ± 1.3)%, and the cytotoxicity rating was grade 1. Significant differences were noted among the four groups (F＝68.250, P < 0.001).

The La-doped TiO₂ film can improve its photocatalytic activity and enhance the antibacterial activity of 3Y-TZP without obvious cytotoxicity.