Pickering emulsions: Development of an all-in-one dermocosmetic formulation

Abstract

Classical emulsions have been recognized as the most widely used vehicle for topical drug delivery as well as cosmetic purposes. In general, an emulsion can be defined as a mixture of two or more immiscible liquids, one of which is finely and uniformly dispersed as globules throughout the second phase. However, since emulsions are thermodynamically unstable systems, a third component, surfactants should be used to stabilize the system by forming a thin film around the globules of the dispersed phase. On the other hand, Pickering emulsion is a relatively new concept and is a type of surfactant-free emulsion stabilized only by fine solid organic or inorganic particles (Albert et al., 2019). Pickering emulsions are a promising alternative as they eliminate surfactant-induced toxicity, improve formulation appearance, provide good viscosity, and promote long-term stability. With these features, Pickering emulsions appear as a satisfactory solution for daily cosmetic/dermocosmetic products as well as for drug delivery to the skin. Depending on the consistency, Pickering emulsions can range from liquid formulations such as lotions to semi-solid formulations such as creams. So, they are promising formulations for the treatment of skin disorders such as atopic dermatitis or eczema as well as skin care product such as anti-aging, moisturizer, or sunscreen (de Carvalho-Guimarães et al., 2022). For the formation of Pickering emulsion, the solid particles adsorbed at the oil-water interface must be fractionally wetted by two phases and the emulsion type (O/W or W/O) can be determined by the wettability of the particles. Hence, organic or inorganic solid particles such as silica, clay minerals, chitin/chitosan, hydroxyapatite, cyclodextrins, cellulose, starch, or minerals like titanium dioxide and zinc oxide, as well as metallic, polymeric, or lipidic nanoparticles can be utilized for creating stable Pickering emulsions. However, the type and morphology of the solid particles can modulate the properties of Pickering emulsions. Hence, choosing the right kind of solid is the essential parameter for the stability of the emulsion. Herein, it is aimed to effectively improve the changes such as fine lines and wrinkles, dryness, and loss of elasticity which are the main signs of skin aging with a single dermocosmetic product. Therefore, in this study, Pickering emulsion formulations were developed by combining different components known to be effective for skin appearance and in vitro characterizations of the formulations were studied.