Properties and applications of liposomes in cosmetics

In recent years liposomes have gained an increased interest as cosmetic ingredients, both for their hydratating-humectant properties and as carriers for (trans)dermal delivery of active ingredients exerting their activity at cutaneous and/or subcutaneous level. In this paper we discuss some aspects of liposomes utilization, their stability in topical forms and some of their possible cosmetic applications as delivery systems for active ingredients. The biological activity of empty liposomes have been recently attributed to different mechanism(s) of action including interaction of liposomes with the superficial keratin, or with the lipid lamellar structures present in the intercellular domain of stratum corneum. Moreover, when liposomes entrapped compounds are utilized, the biological effects of phospholipids should be considered together with their "load" and, eventually, the activity of the metabolites of both the components. A crucial aspect of the cosmetic utilization of liposomes concerns the intrinsic stability of the macromolecular structure of this vehicle, especially when liposomes are incorporated in surfactant containing forms. In this case liposomes can be rapidly solubilized by a large variety of surfactants through a multi step process. In order to overcome this problem, a number of mild formulations that could represent optimal vehicles for liposome incorporation are here proposed.