Rheological Properties of Hyaluronic Acid

Relatively recently, a couple of decades ago, a new group of oligosaccharide phytohormones were discovered and this substantially broadened and changed understanding of certain aspects of the problem of chemical regulation in plants [15]. 

These critical values depend on the type of the solvent. It is known that the nematic liquid crystal phase contains a higher concentration of polymer than does the isotropic phase [23,24]. The liqnid crystal state can be associated with chemical structure as well as size of macromolecules. 

It is known [24] that liquid-crystalline biopolymers are very sensitive to orientation in external fields, that is, electric and magnetic fields, as well under action of pressure or solution fluidity. When other orienting fields are not present, the dynamics of structured systems strongly depend on the shear stress applied. 

The major component of the synovial fluid, that is, hyaluronan, has two main functions namely lubricant and shock impulse damping [25]. Furthermore, hyaluronic acid is a major component of the extracellular matrix of the connective tissue. This kind of polymer should exhibit viscoelastic properties that directly depend on its microstructure and external parameters such as shear rate, stress and temperature. Knowledge of dependence of model synovial fluid viscosity on the shear rate, stress and temperature is very useful for biomedical applications, for example, in treatment of joint diseases. 

The studies by means of NMR and circular dichroism methods [29] made it possible to identify the presence of relatively rigid and more flexible structures alternating within a single hyaluronan chain with a balance between these structures. Extremely high viscosity of hyaluronan solutions was due, on the one hand to its structure and, on the other hand, was conditioned by specific and non-specific intermolecular interactions of macromolecules [29]. It all points to the fact that not only hydrophilic but also hydrophobic interactions play a significant role in stabilization of hyaluronan structure associated with the specific macromolecular structure. 

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