VISCOELASTICITY OF HYALURONAN
Hyaluronan with high molecular weight occupies a great volume in very dilute saline solution, wherein the hyaluronan itself possesses 0.1% or less and the aqueous media occupies the remaining volume. A complex network of HA molecules would form with the increasing concentration on account of the greater frequency of HA molecules interaction.
These networks exhibit some specific properties that isolated hyaluronan molecules do not possess A rapid, short-duration flow through the network allows the solution to exhibit elastic properties, which can distribute load or shear forces within the network. On the other hand, slow fluid flow of longer duration can partially separate and align the molecules, giving them movement and viscous properties.
Fig.2 Modeldescribing the viscous and elastic properties of hyaluronan solutions
The elastic properties of HA were studied in dynamic conditions, i.e., in oscillating rheometers in which the viscous and elastic properties could be separately measured over a broad range of frequencies (0.002-10 Hz). The frequency expresses the rate of energy transferred from the environment to the viscoelastic fluid (Figure 3). The figure demonstrates that the proportion (percentage) of the elasticity increases with the average molecular weight.
Fig.3 The viscoelastic properties of five HA solutions with average molecular weights of 0.7, 1.0, 1.9, 3.2, and 4.3 million. The viscous and elastic properties are expressed as percentages of the total rigidity of the system. The frequency (in Hz) represents the rate of energy input by oscillating movement during measurements. All solutions represented here are measured at the concentration of 10 mg/mL (dissolved in 0.15 mol/L NaCl)
