Improvement of the rheological properties and performance of liquid crystal emulsions: influence of oil addition and/or high-frequency ultrasound treatment

This study investigates the impact of oil addition and processing methods on the physicochemical properties, stability, and skin delivery of vitamin C-loaded cosmetic emulsions containing liquid crystals. The research aims to assess how High-Frequency Ultrasound Treatment (HFUT) and oil incorporation influence particle size, rheology, and bioavailability. Control emulsions and emulsions enriched in vegetable oil were prepared with or without using high-frequency ultrasound treatment and analyzed for particle size distribution, microstructural organization (polarized light microscopy, X-ray scattering), rheological behavior, and stability over time. The ability of these emulsions to protect vitamin C and enhance its skin penetration was evaluated through ex vivo permeation studies using human skin and liquid chromatography analysis. HFUT-treated emulsions exhibited smaller particle sizes, increased viscosity, and improved stability compared to untreated emulsions. Structural analysis confirmed the presence of lamellar liquid crystals, contributing to enhanced formulation stability. Vitamin C retention in the emulsions remained high after prolonged storage. Permeation studies revealed that HFUT emulsions promoted vitamin C retention in the skin, while emulsions that have only been homogenized slightly facilitated deeper penetration into lower skin layers. HFUT treatment enhances the structural integrity and stability of cosmetic emulsions while influencing vitamin C delivery. These findings highlight the potential of process optimization to tailor cosmetic formulations for targeted skin benefits.