 In addition, the aragonite matrices have higher mechanical strength than hydrogels, allowing them to withstand more pressure when pressed into an injured tissue.Alginate is a polysaccharide that readily forms chains; it can be cross-linked at its carboxylic groups with multivalent cations such as Cu2+, Ca2+, or Al3+ to form a more mechanically stable hydrogel.Calcium alginates form polymers that are both biocompatible and non-immunogenic and have been used in tissue engineering applications.