The capacity of hydrogels to absorb a certain amount of water is known as swelling capacity . The rate of swelling defines the swelling kinetics. The capsules of pAAm hydrogels containing different cell loadings were studied. To analyze the swelling kinetic, dry gels were incorporated and removed from buffer phosphate solution (pH 7.2, 25◦C) at regular time intervals, were dried superficially, weighed and reincorporated in the same solution. The mass and the radii of hydrated capsule hydrogels were measured after each time interval. The same procedure was repeated until each sample achieved a constant weight.
To investigate swelling behavior under different ethanol concentration, dried hydrogels were immersed in water-ethanol mixtures with composition ranging from 10 to 90% v/v. The mixtures were kept at room temperature for 24 h to allow the hydrogels reach equilibrium. Afterward, the hydrogels were removed from the solution and blotted with wet filter paper for removal of theexcess solvent on hydrogel surface; then they were weighed. The swelling percentage in water was calculated at different times according to