Natural Emulsifiers of the Alkyl Polyglucoside Type and Their Influence on the Permeation of Drugs

Due to the unceasing progress in design of novel emulsifiers, powerful influence of the ongoing ‘green’ trends in cosmetic industry, but also global environmental concerns, there is an increasing demand in development and application of natural-origin, biodegradable and skin-friendly emulsifiers. The present work aims to provide a deeper insight into the group of alkyl polyglucoside emulsifiers and their prospective impact on drug percutaneous permeation. Complexity of the observed lamellar liquid crystal and lamellar gel phases, which represent the basic mechanism of physical stabilisation by the alkyl polyglucosides, entails a comprehensive physicochemical evaluation of any alkyl polyglucoside-based prospective vehicle, prior to assessing its impact on skin absorption. Research conducted so far has suggested several possible mechanisms of alkyl polyglucoside-mediated percutaneous penetration enhancement, which are carefully elaborated throughout the chapter: (1) the observed similarity between the aforementioned complex structures which dominate alkyl polyglucoside-stabilised systems and the inherent stratum corneum lipid ordering could enhance penetration due to the optimal balance between their order and fluidity, (2) the observed complex colloidal structure may lead to diverse modes of water distribution within these systems, providing sustained skin hydration and hence improved skin permeability, and/or (3) the impact on a drug’s thermodynamic activity, easily tailored by the addition of various co-solvents/potential penetration enhancers.