## 3 Results and Discussion
### Bioactivity and Biodegradability  
The bioactivity and biodegradability of the scaffolds were assessed. After soaking for 3 days, some granular HAp generated on the scaffolds of all groups (Figure 6). Particularly, HAp almost covered the whole scaffolds with the liquid phase, which indicated that the liquid phase improved the HAp formation ability (Figure 6b-e).  
FTIR was performed on group CS-C after immersion for different periods to further study the bioactivity (Figure 7). The absorption bands of silicate group were intense before immersing (0 day). In detail, the absorption bands were recorded at 473 and 794 cm\({}^{-1}\) corresponding to the Si-O-Si vibration and the absorption bands between 922 and 985 cm\({}^{-1}\) corresponded to the Si-O\({}^{-}\) vibration [15; 31]. After immersing, new absorption bands at 1063 and 540-605 cm\({}^{-1}\) were assigned to the phosphate group (PO\({}_{4}\)\({}^{3-}\)), the absorption bands at 1400 cm\({}^{-1}\) were assigned to the carbonate  
Figure 6: Morphologies for groups: (**a**,**a**) CS; (**b**,**b**) CS-A; (**c**,**c**) CS-B; (**d**,**d**) CS-C and (**e**,**e**) CS-D after immersion for 3 days.  
group (CO\({}_{3}\)\({}^{2-}\)), and the bands at 3440 and 1635 cm\({}^{-1}\) corresponded to the O-H absorption [15; 31; 32]. The intensity of silicate group absorption bands were evidently weakened with increasing immersion time. These results further confirmed that there was HAp on the scaffolds after immersing.  
The formation mechanism of HAp on scaffolds could be described as follows: When the scaffolds were immersed in the SBF, Ca\({}^{2+}\) in CaSiO\({}_{3}\) firstly exchanged with H\({}^{+}\) in SBF solution giving rise to the formation of silanol (Si-OH) on the surface of the scaffolds. Thereby, a negatively charged surface with the functional group (Si-O\({}^{-}\)) was formed on the scaffolds. Eventually, Ca\({}^{2+}\) in SBF was attracted to the scaffolds-SBF interface to form a nucleation of HAp. Once the nuclei of HAp were formed, the HAp could grow spontaneously by incorporation of Ca\({}^{2+}\) and HPO\({}_{4}\)\({}^{2-}\) from the SBF.  
The biodegradability of the scaffolds was evaluated by measuring the weight loss (wt %) before and after immersing experiments. Obviously, the weight loss increased with the immersing time (Figure 8a). After immersing for 28 days, the weight loss was 27% for group CS-C, which was lower than that of the scaffolds without liquid phase (41%). This was attributed to the dense structure and the inhibiting effect of the liquid phase on the CaSiO\({}_{3}\) grains. Meanwhile, the compressive strength of the scaffolds with the liquid phase maintained a significant increase in the first 14 days (Figure 8b). This was primarily ascribed to HAp mineralization. After immersion for 21 days, the strength decreased slightly. Therefore, the scaffolds with the liquid phase could maintain mechanical reliability and structural stability for bone repair.  
Figure 8: (**a**) Weight loss and (**b**) change of compressive strength of the scaffolds after immersing for various time periods.  
Figure 7: Fourier transform infrared spectroscopy (FTIR) spectrums of group CS-C scaffolds after immersion for 0, 3, 7 and 14 days.