20 - Vesicular nanostructures for transdermal delivery

Abstract

The history of vesicular skin drug delivery has been started in early 1980s with liposomes made of dipalmitoylphosphatidylcholine (DPPC) and cholesterol (CH) increasing skin deposition and reducing systemic absorption. Twelve years later, a new class of vesicles has been reported to penetrate intact skin delivering therapeutic moieties to the systemic circulation. These vesicles comprised phosphatidylcholine (PC) with edge activators and were termed Transfersomes. Surfactants were used as edge activators and were considered responsible for vesicle deformation providing their unique characteristics. This attracted the attention of researchers to employ vesicular nanostructures in transdermal drug delivery. The effect of vesicle composition on transdermal delivery was studied with various materials substituting surfactants. This developed different vesicles to which alternative terminology was used with variable results being recorded by investigators. For example, skin penetration enhancers were included in the vesicles to impart deformability. This was modified further by adding lyso PC as well to develop invasomes. High ethanol concentration was used as vesicular component to create Ethosomes. A cationic agent was used in the vesicles with biocompatible solvent to develop leciPlex. Stratum corneum lipids were used to devise vesicles which showed good potential for skin drug delivery and were termed stratum corneum lipid liposomes (SCLL). Another research track employed surfactants with CH to develop niosomes which delivered drugs into and through skin. Once again, the efficacy of these vesicles depended on their composition with some of them being flexible enough to advance into and through the skin. The use of vesicle proconcentrates provided another promising research strategy with higher feasibility for scaling up. This chapter will summarize the work done using different vesicular nanostructures in transdermal drug delivery.