Alginate Hydrogels: Properties and Applications

Alginic acid was first discovered by Stanford and recognized asthe structural component of marine brown algae (Phaeophyceae) [136] where it constitutes, as an insoluble mixture of calcium,magnesium, potassium and sodium salts [62], up to 40% of thedry matter. In the first half of the twentieth century, the repeatingunits constituting the polysaccharide backbone were identifiedwith mannuronic and guluronic acids [7, 47, 120]. The contentof the two different uronic groups in alginate samples was foundto vary over a wide range depending on their source. Nowadays,to underline the chemical inhomogeneity of this polysaccharide,the term alginate is used to describe a family of polysaccharides[113] produced by brown algae and bacteria. In seaweeds, alginatescontribute the strength and flexibility of the plant. Indeed, alginateshave the same morphophysiological properties in brown algae asthose of cellulose and pectins in terrestrial plants [38]. The large-scale production of alginates is exclusively based on the harvestingof brown seaweeds belonging to the family of Laminaria (of the species hyperborea, digitata, japonica), to Macrocystis pyrifera, and to Durvillea antarctica. Alginate composition depends on the seasonal and growth conditions as well as on the parts of the plantthat the alginate is isolated from [3, 73].