A gravimetric method was employed to investigate the swelling behavior of freezedried hydrogels. The hydrogel samples were subjected to incubation at 37 °C in pH 7.4 PBS until they reached equilibrium weight. Excess water absorbed by the swollen hydrogels was removed using a filter paper, and the samples were weighed again. Next, the samples were dried until a constant weight was achieved. The swelling ratio was then calculated using the following equation: Percentage of swelling (%) = (Wwet-Wdry)/Wdry × 100, where Wwet and Wdry refer to the weight of wet and dry hydrogels respectively.