Design of novel starch-based Pickering emulsions as platforms for skin photoprotection

Abstract

Green coffee oil and modified starch were recently found to have an enhanced protection effect against UV radiation. Therefore, this work aimed to develop an innovative sunscreen formulation based on Pickering emulsions concept, i.e., surfactant-free emulsions stabilized by physical UV filters associated natural oils as a key strategy for prevention against UV-induced skin damage. The Pickering emulsions of different compositions were characterized in terms of pH, mechanical, physical and microbiological stability by a thorough pharmaceutical control. In addition, the sun protection factor (SPF) as well as the in vitro and in vivo biological properties of the final formulations, including Episkin®, HRIPT and sunscreen water resistance. Formulation studies demonstrated the addition of physical UV filters was beneficial, leading to the inclusion of ZnO and TiO2 to ensure a high SPF against UVA and UVB, respectively. Although starch particles presented no intrinsic photoprotection properties, they proved to be a SPF promoter by a synergistic effect. Green coffee oil was the selected natural oil due to the highest SPF, when compared to other natural oils tested. Besides the excellent sunscreen activity confirmed by in vitro and in vivo results, the final formulations proved to be also suitable for topical use according to the rheological assessment and stability throughout the study period (3months). In conclusion, the combination of three multifunctional solid particles and green coffee oil, contributed to achieve a stable and effective innovative sunscreen with a wide range of UV radiation protection.

Pickering emulsions: Preparation processes, key parameters governing their properties and potential for pharmaceutical applications

“…Tan et al [252] showed that the API bioaccessibility was improved by a factor of 5 after the in vitro digestion of Even if these emulsions were intended for a food application and not for a pharmaceutical one, they all used biocompatible oil making these systems potential pharmaceutical Pickering emulsions, especially for oral administration. 45…”

Recent developments in Pickering emulsions for biomedical applications

“…Other recent work has used chitosan based Pickering emulsions as a method to enhance wound healing, where the synergistic effect of the cargo therapeutic and other components of the Pickering emulsion demonstrated improved functioning compared to the drug alone. [16] Another innovative topical application of Pickering emulsions is for sunscreens, [25,26] where the emulsifying particles can be physical UV filters in combination with an encapsulated active agent, such as melatonin. [27] Such formulations can present a stable and effective sunscreen with the added benefit of protection against oxidative stress, thanks to melatonin's free radical scavenger and antioxidant activity.…”

Can natural products improve skin photoprotection?

“…Chemical UV filters are incorporated into sunscreen products to reduce skin photoaging and prevent skin cancer (Foley et al 1993;Marto et al 2016). The main chemical filters include paraaminobenzoic acid, benzophenones, cinnamates, and benzimidazole sulfonic acids.…”