## 3 Results and Discussion
### Bioactivity  
We uses an SBF solution in which to soak test pieces for 7 days to evaluate the bioactivity of the titanium sheet after anodization, alkali treatment, and acid treatment. The results showed that there were different mineralized crystals on the surface of the titanium sheet (Figure 7). Mineralized crystals on the surface were mainly calcium carbonate (CaCO\({}_{3}\)). Calcium carbonate has three crystal forms: rhombic calcite, needle-shaped aragonite, and spherical vaterite [45]. Diamond-shaped crystals observed in the Ti group were calcite. Mineralized crystals observed in the TNTs group were not calcium carbonate but mineralized crystals resembling mountain shapes. A mineralized layer other than calcite was observed in the alkali-treated group, and needle-shaped crystals in the mineralized layer were aragonite. In the acid treatment group, calcite deposition was observed in holes of the titanium piece. In the CaP solution group, flaky crystals that originally formed on the surface of the test piece were also transformed into needle-shaped aragonite (Figure 7). In the CoHA solution group, the calcium and phosphorus deposits deposited on the surface under the influence of cobalt ions were transformed into round and rod shapes. This was similar to a previous report on CoHA which confirmed that cobalt ions affect the morphology of surface deposits [46]. [PERSON] et al. reported that the circular morphology of HA can enhance cells adhesion [47]. However, it was confirmed from SEM images that irradiation via LAB induced HA deposition to increase the surface bioactivity. The surface elemental compositions of groups of test pieces after being soaked in SBF solution for 7 days by an EDX analysis are shown in Table 3. The deposition of HA after LAB irradiation was significantly greater than that of samples without LAB treatment. The CaP solution group showed that titanium elements of TNTs, NaOH, and HCl decreased, which represented an increase in the deposition area of HA. After the CoHA solution was irradiated, cobalt was observed among the groups to show the deposition of CoHA. Comparing the Ca/P ratio on the surface of each group of test pieces showed that the Ca/P ratio increased after LAB treatment. In particular, the Ca/P ratios of the TNT CoHA and NaOH CoHA groups were both 1.67, which were similar to the Ca/P ratio of human bone (Table 3). This shows that the surface after LAB treatment was calcium-deficient HA. However, calcium-deficient HA can release ions into SBF to facilitate the deposition of HA. ATR-FTIR spectra show characteristic peaks of test pieces after soaking in the SBF solution for 7 days (Figure 8A-C). There were no significant differences in samples of each group. Functional groups such as P-O, C-O, and O-H were detected on the surface. Bifurcation (1038 cm\({}^{-1}\)) before soaking in SBF indicated that the phosphate signal was weak (Figure 5B,C). The disappearance of the branching of the PO\({}_{4}\)\({}^{3-}\) group after SBF soaking indicated that the crystallinity of HA had greatly improved. Figure 6: Proliferation determined according to 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolzolium bromide (MTT) assay of MG63 cell for 24 and 72 h. (**A**) LAB CaP solution. (**B**) LAB CoHA solution. Means with different letters were significantly different (\(p<0.05\), mean \(\pm\) SD, \(n=4\)). Crystal structures of different surfaces after being soaked in SBF for 7 days by LAB treatment were analyzed by XRD (Figure 5D-F). Each group of samples had a diffraction front showing HA after being soaked for 7 days. However, most of the non-irradiated and CaP solution-irradiated groups were mainly composed of calcium carbonate and titanium [48]. The sample with the CoHA solution and LAB mainly had an HA structure after being irradiated. This was similar to ATR-FTIR results. Deposition of the CoHA solution after irradiation was better dissociated in solution. Therefore, more ions were induced to bind and deposit HA.