Nanoformulation des corps gras. Nanocapsules, nanoémulsions

Abstract

Nanocapsules (submicron particles, of diameter 250 nm, with an oily core enclosed in a solid polymeric shell) were prepared using a controlled nanoprecipitation process with preformed polymers (for example poly-ε caprolactone, polyethylene adipate). Nanocapsules formed by this method contain up to 7.5% oil (1% polymer). The following properties are observed using nanocapsules : improved oxygen stability of active ingredients (retinal, β carotene), significantly improved vectorisation (up to 3 times) in skin and a reservoir effect. Due to their solid polymer shell nanocapsules are stable when formulated and penetrate intact into the superficial layers of the epidermis. Nanoemulsions wich are very fine oil-in-water dispersions having droplet diameter smaller than 100 nanometers, were prepared with a high shear device. Two major sources of unstability were identified and extensively studied: Ostwald ripening and depletion induced floculation following the addition of thickening polymers. The control of these two mechanisms allowed the industrial production of a large variety of cosmetic products. The nanoemulsions are easily valued in skin care due to their good sensorial properties and their biophysical properties.