Hyaluronan (Hyaluronic Acid) chemistry and its applications
Hyaluronic acid, also known as hyaluronan, is a hydrated gel and comprises repeating units of glucuronic acid (GlcUA) and N-acetylglucosamine (GlcNAc) (Fig. I.1).
Production and recovery of hyaluronic acid has gained great importance due to its numerous clinical applications.
Hyaluronic acid is present in all vertebrates. High concentrations are found in the synovial fluid between joints, umbilical cord, skin, and the vitreous body of the eye. It is estimated that in the body of a person of 70 kg, about 15 g hyaluronan is found in different tissues, of which one third is turned over every day. The human skin contains almost half of the hyaluronan in the body.
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| Fig. I.1: Repeating unit of hyaluronan |
Although hyaluronic acid has a very simple structure, almost everything else concerning the molecule is unusual. Sometimes its role is mechanical and structural (as in the umbilical cord, synovial fluid and the vitreous humor) whereas sometimes it interacts in tiny concentrations in cells to trigger important responses. Initially, hyaluronan was believed to be an inert compound having no specific interaction with other macromolecules. However, from the discovery of the interaction of hyaluronan with cartilage proteoglycans by Hardingham et al. a large number of reports have been published on the role of hyaluronan in cellular activity, migration, mitosis, inflammation, cancer, fertilization and angiogenesis.
The most significant clinical applications of hyaluronic acid are in the area of ophthalmology (in eye surgery), orthopedics (arthritis), and wound healing (diabetic ulcer, skin burns). Emerging uses include drug delivery, coatings, implants and therapeutics related application. In cosmetics is used as a hydrating and antiaging material as hyaluronan gels and creams.
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