Hydrogels are water-swollen networks of hydrophilic homopolymers or copolymers. They are three-dimensional and they can be formed by covalent or ionic bonds. The molecular van der Waals forces and hydrogen bondings can serve as cross-links, thus forming swollen networks, which behave as hydrogels. In biomedical and agricultural applications, there are normally three types of hydrogels, including neutral hydrogels, ionic hydrogels, and swollen interpenetrating polymeric networks.

Preparation of swollen, hydrophilic, polymeric networks are usually achieved in two techniques as following:

a. By cross-linking of a homopolymer or copoloymer in solution with subsequent swelling in water or other aqueous solution.
b. By simultaneously copolymerization and cross-linking of one or more monofunctional and one multifunctional monomer, followed by swelling in an appropriate aqueous solution.

Since PGA is an all natural biodegradable biopolymer of glutamic acid, it is the top choice as the backbone material for making hydrogels for use in biomedical as well as environmental applications. The PGA hydrogels show an outstanding water absorption up to approximately 5000 times of its weights It is non-toxic, and also environmentally friendly. It can be best used in seed-coating; soil renovation; adding in controlling the spreading of the desert and turning it into green agricultural field; and in controlling the animal fecal waste and composting; in water treatment; in hygiene products such as diapers or tampons; and many other possible industrial applications.