30.06.2020 by Dr. Shona Marsh

Rheology: De-stressing the test of time

We discuss how rheology can be used to characterize anti-aging dermal fillers.

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.

The viscosity, viscoelasticity and TackinessTackiness describes the interaction between 2 layers of identical (autohesion) or different (cohesion) materials in terms of surface stickiness.tackiness of HA fillers have been measuring using the Kinexus rotational rheometer. Full rheological characterization of these samples is important to determine their performance. For example, to reduce pain upon injection it is crucial to understand the extrusion force, gel strength and resistance to deformation of the material.

To see the results from the study you can read the application note here. If you are interested in other applications of HA, you can also read about the rheological properties of OVDs (Opthalmic Viscosurgical Devices) which are solutions or gels that protect the corneal endothelium from trauma during eye surgery.