Development, physico-chemical characterization and in-vitro studies of hydrogels containing rosmarinic acid-loaded nanoemulsion for topical application.

Objectives: Natural sources with antioxidant activity, such as rosmarinic acid (RA), have been considered as an interesting approach for the development of new anti-ageing skin products. In this context, this study aimed to develop hydrogels containing RA-loaded nanoemulsions and evaluate the effect of the addition of Tween 80 (a nonionic cosurfactant) in formulations intended to be used for topical application.

Methods: Physico-chemical characterization, in-vitro release and skin retention/permeation from hydrogels of RA-loaded nanoemulsions (containing or not Tween 80) were evaluated. The RA-loaded nanoemulsion safety profiles were also investigated in keratinocytes (HaCaT cells).

Key Findings: It was observed that all formulations presented adequate physico-chemical characterization for topical application. Furthermore, the results also demonstrated that the presence of Tween 80 decreased the droplet size and polydispersity index of nanoemulsions and hydrogels. An extended RA release was noted for the hydrogels. However, when comparing the hydrogels, a positive effect of the presence of Tween 80 on RA retention/permeation in total skin was seen. The RA-loaded nanoemulsion safety profiles demonstrated a good tolerability (3.125-100 μm) in HaCaT cells.

Conclusions: The overall results demonstrated that the formulations developed in this study can be considered as a suitable carrier for RA in a topical application targeting new anti-ageing skin care products.