Valorizing Sicilian Grape Pomace for Sustainable Nanocosmetic Applications

(1) Background: Grape pomace (GP), a major by-product of winemaking, is a sustainable source of bioactive polyphenols with antioxidant, anti-inflammatory, and antimicrobial properties, although their instability limits cosmetic applications. This study aimed to valorize GP through a green extraction process and improve its incorporation and apparent stability in cosmetic formulations through SLN-based systems. (2) Methods: GP extracts were obtained using an eco-friendly extraction method and encapsulated using a W/O/W double emulsion-solvent evaporation technique; nanoparticles were characterized (size, polydispersity, zeta potential) and incorporated into cosmetic formulations compared with a blank and a formulation containing free extract. (3) Results: GP-SLNs exhibited suitable physicochemical properties and preserved antioxidant activity, as confirmed by DPPH and ORAC assays; SLN incorporation appeared to preliminarily improve the photostability profile of the formulation under UVA irradiation conditions; in vivo tests showed enhanced skin hydration and moderate occlusivity, while stability studies confirmed consistent color, odor, pH, and viscosity over 60 days; microbiological analyses demonstrated safety and concentration-dependent antimicrobial activity. (4) Conclusions: SLN encapsulation preserved GP bioactivity and improved formulation stability and performance, supporting its potential use in multifunctional cosmetic products.