The plane gels were formed by adding 5 mL of 0.5 wt% alginate solution into a plastic petri dish. For initiating the gelation, 6 mL of CaCl2 1 wt% with the desired thickening agent was carefully poured over alginate solution. Finally, the obtained hydrogels were stored in CaCl2 solutions (pH 5, 1 wt%) to complete the reticulation process.