2.4. The Hydrolytic Degradation of Super-Macroporous Pullulan Cryogels

The hydrolytic degradation behavior of pullulan cryogel was investigated gravimetrically. Briefly, cryogel weighing approximately 15 mg was placed in tubes containing 15 mL of different pH buffer solutions (stomach pH value of ~1.0, physiological pH value of ~7.4, and duodenum pH value of ~9.0) and allowed to swell for 10 min. Then, the weight of the swollen cryogel was recorded and again put back into the tubes. The tubes were placed in a shaking water bath at 37.5 °C. The percentage weight loss of cryogels over time was calculated using Equation (5) by weighing the swollen pullulan cryogels at certain times [29]. Hydrolytic degradation studies were repeated three times to evaluate the accuracy, and the mean values were reported by calculating the standard deviations.

where m_t represents the weight of the cryogel at time t, and m_i represents the initial weight of the swollen cryogel.