Stability and In Vitro Skin Compatibility of an Adapalene-Loaded Solid Lipid Microparticle Dispersion

Abstract

A novel adapalene-loaded solid lipid microparticle (SLMA) dispersion composed of topically approved ingredients exhibited follicular penetration and a targeted drug release in sebum. In the present study, the stability regarding particle size, thermoanalytical properties, drug content, and pH value was tested after storage at 5°C, 23°C, and 40°C over 12 weeks. Additionally, a thermal cycling study was performed in order to consider storage temperature variations. The dermal compatibility was tested on a HaCaT monolayer in comparison to the Differin ® cream in order to evaluate potential local side effects. The SLMA dispersion displayed a pronounced physical stability at 5°C including a constant particle size as well as melting point. Compared to that, the physical stability was limited at 40°C with significant particle growth and a significantly increased melting temperature, whereas the properties just slightly changed during storage at 23°C. The drug content and pH value remained the same. The skin compatibility test revealed a high cell viability of about 90% for all investigated dilutions of the SLMA dispersion probably due to the presence of glycerides and lecithin. On the contrary, the dilutions of the Differin ® cream caused a significant decrease of the cell viability to approximately 11% based on its ingredients.