Related topic: Solid-in-oil technique to increase skin permeation

Solid-in-oil (S/O) nanodispersion systems represent a new technology that has been developed in the last decade. Nano-sized, solid-state, hydrophilic drug molecules can be dispersed in an oil vehicle by coating the drug with hydrophobic surfactants; these materials are designated here as S/O nanodispersions. Conventional S/O nanodispersion systems were devised to maintain hydrophilic enzymes in their active form in organic solvents. Because the coated molecules are stable in non-aqueous media, S/O nanodispersion systems can be successfully applied in oral and skin drug deliveries. It is known that the permeability of hydrophilic drugs through the skin decreases when the molecular weight of the drug exceeds 500 Da. In addition, hydrophobic molecules tend to permeate through the skin preferentially, compared with hydrophilic molecules, because the outermost layer of the skin is hydrophobic. In our experiments, the permeation of hydrophilic biomolecules such as peptides and proteins through the skin increased by 4-7 times when their molecules were coated with lipophilic surfactants and dispersed in an oil vehicle. Here, we introduce an efficient method for drug delivery through the skin, using the S/O nanodispersion technique.