The reticular microstructure of the HA-based powder gel was induced by cross-linking and analyzed using a scanning electron microscope (SEM, S-4700, Hitachi, Tokyo, Japan). The swelling properties of the HA-based powder gel were measured by incubating it in PBS at room temperature. The swelling ratio was measured by comparing the change in the wet weight of the hydrogel before and after 3 days of incubation. The percentage of water absorbed (Wa) was calculated by the following formula: Swelling ratio (%) = ((Ww-Wi)/Wi) X 100 % (Ww: wet weight of hydrogel; Wi: initial weight of hydrogel).