Design of sustainable lip gloss formulation with biosurfactants and silica particles.

Objective: The main objective of this study was to design a sustainable lip gloss from water-in-oil emulsions by understanding the rheology of combining biosurfactants (rhamnolipids and sophorolipids) with silica particles (Aerosil powders). The different parameters consisted of the silica particle diameter size, the concentration of the particles within the formulation, alongside the different types of biosurfactant and oils used. The experimental results could provide information on the formulation design of cosmetic emulsions such as lip products and foundations.

Methods: One parameter was varied each time, while the rest were kept constant in order to determine their effect on the viscosity profile of the formulations. A traditional mechanical rheometer was used in order to measure the bulk viscosity profiles of the different formulations, over a wide range of shear stress applied.

Results: The larger silica particle diameter size indicated an increase in the viscosity of the formulations, as yield stress was also generated for the specific diameter of 14 nm. It was also found that as the particle concentration increased, the viscosity increased as well. Rhamnolipids and sophorolipids indicated very similar behaviour, meaning that the biosurfactant acts as an emulsifier and does not impact the system's rheological behaviour. The replacement of silicone oil with other natural oils was only successful with canola, and castor oil, since jojoba, squalene and mineral oil were not stabilized.

Conclusion: The lip gloss was designed by water-in-oil emulsions which were stabilized by biosurfactants and the rheology of the oil phase was enhanced by silica particles. The formulation rheology gave a stable emulsion, the shear-thinning effect ensured easy applicability, whereas the viscosity and elasticity provided nice hold on the lips.