Lipid-based Janus nanoparticles for pharmaceutical and cosmetic applications: Kinetics and mechanisms of destabilization with time and temperature.

The aim of this paper is to investigate the time and thermal stability of innovative multicompartmental nanoparticles. These particles, having a hydrophilic side and a hydrophobic side, belong to the family of Janus particles and are promising tools to carry active ingredients with opposite solubilities in a unique nanocarrier. The stability of nanoparticles obtained with mainly two types of polyoxylglycerides (Labrafil® M2125 CS and Labrafil® M1944 CS) has been investigated. The suspensions describe a two-step maturation/destabilization process with an Ostwald ripening phase followed by the coalescence of the particles. The effect of lipid composition and temperature on these steps has been investigated in deep as stability with temperature is a critical parameter to consider in order to envisage the development of any formulation for pharmaceutical or cosmetic uses. These nanoparticles were particularly stable at room temperature as their hydrodynamic diameter did not change significantly for 20 months. Contrarily, a strong dependency to temperature appears when storage temperature increases from 25 °C to 43 °C. Indeed, Labrafil® M1944 CS seemed to undergo a progressive destabilization where a significant increase of particles size is visible from 25 °C and phase separation occurred after 4 months at 32 °C. At the opposite, Labrafil® M2125 CS remained stable until 36 °C and reached a threshold temperature between 32 °C and 36 °C after which Labrafil® M2125 CS underwent a consequent increase of particles size at the longer time, i.e. after 6 months. Moreover, Labrafil® M2125 CS formulation was stable at least 3 months at 43 °C.