Development of a photoprotective and antioxidant nanoemulsion containing chitosan as an agent for improving skin retention

Sunscreens are destined to topical application and should protect skin against ultraviolet radiation; furthermore, they are toxic substances and should not reach the bloodstream, so they must be retained in the skin. In the present work, an oil‐in‐water photoprotective and antioxidant nanoemulsion (NE) containing chitosan was developed. Preliminary studies were performed aiming to choose the surfactant to be used in this NE; stability of the formulas was determined by dynamic light scattering after their preparation and after 7 days. A blend of surfactants, polyoxyethylene sorbitan monooleate, and sorbitan monooleate was selected for the preparation of the NE, as well as the following organic sunscreens: benzophenone‐3, diethylamino hydroxybenzoyl hexylbenzoate, octocrylene and octylmethoxycinnamate, and also pomegranate antioxidant extract and chitosan. The antioxidant extract with the highest antioxidant activity was chosen based on a screening of plant extracts by DPPH• (2,2‐diphenyl‐1‐picrylhydrazyl) assay. Photostability of the sunscreens and in vitro efficacy and safety of the formulations were also evaluated. Results showed that the developed photoprotective and antioxidant NE containing chitosan was stable for at least 6 months, photostable when irradiated in a solar simulator, and effective. Additionally, chitosan acted by promoting retention of the formulation in epidermis, thus increasing formulation safety.