To characterize the swelling, r2 hydrogels were cut into 8 mm diameter discs, blotted with filter paper and their initial weights were recorded (M 0 ). The samples were then incubated in 1 mL of PBS buffer at 37 °C for indicated duration. At selected time intervals, the excess liquid was removed from the swollen gels and the samples were reweighed (M 𝑡 ). Hydrogels were then replenished with fresh buffer. From these data, swelling ratios (