Simultaneous encapsulation of zinc oxide and octocrylene in poly (methyl methacrylate-co-styrene) nanoparticles obtained by miniemulsion polymerization for use in sunscreen formulations

Polymer nanoparticles have been used by the cosmetic industry since the last decade. Nanoencapsulation of sunscreen is performed to prevent photodegradation and skin accumulation, reducing its toxic effects. The aim of this study was to develop a new sunscreen with the simultaneous encapsulation of zinc oxide nanoparticles (ZnO) and octocrylene in poly-styrene-co-methyl methacrylate (PMMA/PS) nanoparticles via minimemulsion polymerization, and to evaluate its efficacy as sunscreen and biocompatibility in human dermal fibroblasts. Both inorganic and organic filters were successfully encapsulated in PMMA/PS nanoparticles with high encapsulation efficiency and physical-chemical properties desirable for use in sunscreens. The obtained nanoparticles (10% or 20%) were incorporated into Artistoflex AVC (R) gel resulting in a semi-solid formulation with homogeneous aspect and without lumps, color white and pH close to the pH of the skin. The semi-solid formulation containing ZnO and octocrylene in PMMA nanoparticles exhibited a good solar protection factor (SPF > 30) being considered a good UVA sunscreen receiving a 4-star rating according to the Boots Star Rating System. Lastly, cytotoxicity studies on human dermal fibroblasts showed the biocompatibility of sunscreen, this being a promising system for future studies in vivo.