2.5. Swelling ratio test

The measurement of the hydrogel's swelling rate was conducted using the gravimetric method. The hydrogel was immersed in phosphate-buffered saline (PBS) at a temperature of 37 °C for a duration of 24 h. Subsequently, any extra liquid was removed by gently blotting the hydrogel with filter paper. The hydrogel was then accurately weighed and identified as W_s for labeling purposes. The hydrogel underwent freeze-drying and subsequent weighing and was subsequently designated as W_d. The swelling rate of the hydrogel can be determined using the following formula: swelling rate (%) = (W_s - W_d)/W_d × 100.