The water absorbing capacity of hydrogels is strongly influ- enced by their chemical composition. It depends on the ratio and nature of ionic and non-ionic functional groups (Omidian et al., 2010). So, a preliminary study was conducted on the swelling kinetic of beads. Fig. 4a represents the dynamic swelling behav- ior of magnetic beads in distillated water. Initially, the rate of water uptake was sharply increased and then began to level off. Comparing the dynamic swelling of beads, it is clear that water uptake and rate of swelling of hydrogels was affected by the composition of beads. Maximum and minimum swelling capacity was obtained for magnetic-free (CMChitoCar) and mCMChitoCar2 hydrogels, respectively. The swelling capacity of all magnetic beads was obtained lower than the magnetic-free beads and this decre- ment in water absorbency can be attributed to the presence of Fe3O4 nanoparticles. The decrease in the swelling of magnetic beads is arisen from: (a) decrease in the ratio of hydrophilic and anionic functional groups due to the introduced non-ionic Fe3O4 nanoparticles and (b) the interaction between magnetic nanopar- ticles and polymeric chains results in more crosslink points and thereby decrease in swelling capacity (Philippova et al., 2011). In the case of mCMChitoCar3 beads, the swelling capacity was obtained higher than that of other magnetic beads. The weight ratio of two biopolymers in this sample was not equal and the content of -carrageenan component was high. The reason for the high swelling may be due to the high content of -carrageenan which contains sulfate groups.