Viscoelasticity of hyaluronic acid with different molecular weights

Storage and loss moduli of hyaluronic acid solutions with different molecular weights were observed as a function of frequency in the presence of sugars and salts. The hyaluronic acid solutions of higher molecular weight (Mw > 17 × 10⁶) fractions showed entanglement, whereas lower molecular weight fractions did not. For inducing the entanglement of molecular chains of hyaluronic acid, increasing the molecular weight of hyaluronic acid was more effective than increasing the concentration of the lower molecular weight fractions (Mw = 7.8 × 10⁵). Glucose, fructose, galactose, and sucrose increased both storage and loss moduli, while NaCl, KCl and CaCl₂ decreased both moduli. It is suggested that sugars create hydrogen bonds and strengthen the transient network. Cations shield the electrostatic repulsion of hyaluronic acid molecules, and the polymer chains are shrunk into compact coils from expanded stiffened coils.