The prepared HA-based powder gel was uniformly rehydrated (Fig. 3a). A SEM image of cross-linked and freeze-dried HA-based hydrogel is presented in Fig 3b. The HA-based powder gel showed a swelling ratio of 671.4 % in PBS (Fig. 3c), which means that, in this study, the powder gel has sufficient capacity to load the BMP-2 solution. The HA-based powder gel was mixed with β-TCP spherical powder using the in situ mixing process described above.
Fig. 3  a SEM images of cross-linked and freeze-dried HA-based hydrogel; b Images of the hydrated HA-based powder-gel; c Swelling ratio of the HA-based powder-gel