Evaluating the Rheological Properties of Hyaluronic Acid Hydrogels for Dermal Filler Applications
Application Note Feb 27, 2015
Malvern Instruments Limited
Hyaluronic acid (HA) is a naturally occurring polysaccharide frequently used as a functional ingredient in many topical and subcutaneous anti-ageing treatments such as dermal fillers, which exploit the polymer’s unique viscoelastic properties for effective soft tissue augmentation. When administered subcutaneously, HA builds an elastic network within wrinkles and rhytides to give the skin a plumper and fuller look. Naturally occurring HA has a half-life of less than three days so increasing the durability of the polymer is essential to developing products with greater clinical persistence and an acceptable shelf life. Increasing both the molecular weight (MW) and degree of cross-linking of the polymer is a proven strategy for improving mechanical strength and extending degradation times. However, these characteristics also impact other properties of the HA such as viscosity and viscoelasticity.
To formulate successfully with HA it is essential to understand the impact of factors such as molecular weight, molecular structure, concentration and degree of crosslinking on rheological characteristics such as viscoelasticity which are directly linked to aspects of product performance. Linking structural characteristics to product performance, via rheological properties, supports smart, fast, and effective formulation.
The following study shows how rheology and particle size measurements can be used to characterize the physical properties of HA dermal fillers.