Émulsions stabilisées par des particules polymériques biodégradables : études physico-chimiques et évaluation pour l'application cutanée

摘要

The so-called Pickering stabilization is based on the use of solid particles instead of emulsifiers. Their strong adsorption at interfaces confers rigidity preventing them from coalescence. This work is divided into four main parts. The first part deals with the manufacture of these particles and their physicochemical characterization. A second part deals with the O/W emulsions formulation according to two different methods and their characterization. The third part is an investigation into the behavior of these particles at the O/W interface by small angle neutron scattering. The last part deals with the evaluation of these emulsions for their application to skin delivery. This work aims at the preparation of Pickering emulsions using biodegradable polymeric particles. Individual particles formed from diblock copolymers such as: PCL-b-PEG and PLA-b-PEG, were made by an innovative nanoprecipitation process. They were characterized in terms of their size and stability. Their internal structure was also investigated by NMR and cryo-TEM. Their ability to stabilize highly concentrated O/W emulsions has been demonstrated. The impact of the emulsification process on the final properties was emphasized and the adsorption of particles as tight necklaces at the interface was visualized by neutron scattering and freeze-fracture electron microscopy. The skin absorption of retinol from these innovative emulsions showed enhanced accumulation of the asset in the stratum corneum compared to conventional surfactant-stabilized emulsions. Such skin absorption of retinol was shown to depend on the manufacturing method of the emulsions. Particles in aqueous suspension were also tested for encapsulation and delivery of retinol in skin. The results showed the influence of the internal structure of the particles (PCL or PLA) on the absorption of retinol in the skin. The use of biodegradable polymers brings new perspectives in the formulation of Pickering emulsions for cosmetic or pharmaceutical use, while avoiding the effects of inorganic particles considered hazardous to human health