Table 1 Definition and characteristics of hyaluronan (hyaluronic acid) and hylans

Hyaluronan (hyaluronic acid) or sodium hyaluronate

Long, nonsulfated, straight chains of variable length

Repeating disaccharide unit of N-acetylglucosamine and glucuronic acid

Forms a randomized coil in physiological solvents

Average MW 4–5 million Da

Hylans

Crosslinked hyaluronan chains in which the carboxylic and N-acetyl groups are unaffected

MW of Hylan A is 6 million Da

Can be water-insoluble as a gel (e.g. hylan B) or membrane bound