Stringiness of hyaluronic acid emulsions

Abstract

Objective Cosmetic emulsions containing hyaluronic acid are ubiquitous in the cosmetic industry. However, the addition of (different molecular weight) hyaluronic acid can affect the filament stretching properties of concentrated emulsions. This property is often related to the “stringiness” of an emulsion, which can affect the consumer's choice for a product. It is thus very important to investigate and predict the effect of hyaluronic acid on the filament stretching properties of cosmetic emulsions. Methods Model emulsions and emulsions with low and high molecular weights are prepared and their filament stretching properties are studied by the use of an extensional rheometer. Two different stretching speeds are employed during the stretching of the emulsions, a low speed at 10 µm/s and a high speed at 10 mm/s. The shear rheology of the samples is measured by rotational rheology. Results We find that filament formation only occurs at high stretching speeds when the emulsion contains high molecular weight hyaluronic acid. The formation of this filament, which happens at intermediate states of the break‐up, coincides with an exponential decay in the break‐up dynamics. The beginning and end of the break‐up of high molecular weight hyaluronic acid emulsions show a power law behaviour, where the exponent depends on the initial stretching rate. At a lower stretching speed, no filament is observed for both high molecular weight and low molecular weight hyaluronic acid emulsions and the model emulsion. The emulsions show a power law behaviour over the whole break‐up range, where the exponent also depends on the stretching rate. No significant difference is observed between the shear flow properties of the emulsions containing different molecular weights hyaluronic acid. Conclusion In this work, we underline the importance of the molecular weight of hyaluronic acid on the elongational properties of concentrated emulsions. The filament formation properties, for example the stringiness, of an emulsion is a key determinant of a product liking and repeat purchase. Here, we find that high molecular weight hyaluronic acid and a high stretching speed are the control parameters affecting the filament formation of an emulsion.

Formulation and Characterization of Nanoemulsion Incorporating Chamomilla recutita L. Extract Stabilized with Hyaluronic Acid

“…The viscosity increase resulting from HA inclusion is linked to the hygroscopic nature of the molecule. This property attracts water to its polysaccharide structure, forming a three-dimensional network capable of enhancing the viscoelasticity of emulsifying systems [ 40 ]. The rheograms revealed that as shear force increased, viscosity tended to decrease, a characteristic of formulations with pseudoplastic flow [ 14 ].…”

Novel conformation of hyaluronic acid with improved cosmetic efficacy

“…Hyaluronic acid (HA) is a naturally occurring anionic non-sulfated glycosaminoglycan with a broad physiological distribution [1][2][3] ; approximately 50% of the total body HA can be found in the skin. 2 The building blocks of HA are polymeric disaccharides composed of D-glucuronic acid and N-acetyl-D-glucosamine linked by alternating β-1,3 and β-1,4 glycosidic bonds.…”