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

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.

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).

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.

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.