A review of the designs and prominent biomedical advances of natural and synthetic hydrogel formulations

Hydrogels are three-dimensional hydrophilic polymeric networks, capable of absorbing large quantities of water and biological fluids and simulating biological tissue when swollen. Hydrogels are frequently explored for use in numerous biological and biomedical applications due to their desirable properties. Hydrogels are characterized as either synthetic, natural or hybrid, based on the nature of their constituent polymers. The use of natural polymers in hydrogels for biomedical applications is advantageous due to their biocompatibility, biodegradability and non-toxicity, whereas, synthetic polymers are hydrophobic, possessing strong covalent bonds within their matrix, which improves the mechanical strength, service life and absorbability of the gels. Their polymeric crosslinking structure defines their physical or chemical nature, while their polymeric composition indicates whether they are homopolymeric, copolymeric or multipolymeric. All the classifying properties of hydrogels affect their applicability and types of areas in which they can be incorporated. In this review, we critically detail the most common natural and synthetic hydrogel formulations, their designs and their most significant and current biomedical applications.