3.5. Swelling and Biodegradation of Hydrogels Studies

The mass swelling ratio (MSR) of hydrogels was determined at 37 °C during 80 h of incubation in PBS. Samples (approximately 0.5 g) in triplicate were submerged in a PBS solution (10 mL) for a given time, and their weights were taken after removing the excessive surface water. The mass swelling ratio was calculated using the following formula:

where:

W1 is the weight of the initial hydrogel;

W2 is the weight of the swollen hydrogel.

In order to evaluate the percentage of degradation, the hydrogel samples were immersed in PBS at 37 °C for 4 weeks; most importantly, the medium was replaced with fresh PBS every one week. At the end of the experiment, the samples were dried in a vacuum for 48 h. The degree of degradation of hydrogels (in triplicate) was determined by the weight loss (WL) of the samples according to the equation:

where:

WL is the weight loss;

W1 is the weight of dry sample before degradation;

W2 is the weight of the dry sample after degradation.