Enhanced delivery of retinoic acid to skin by cationic liposomes.

We studied the delivery of retinoic acid to skin by using cationic liposomes consisting of double-chained cationic surfactant, phosphatidylcholine (PC) and retinoic acid in excised guinea pig dorsal skin. Egg yolk PC liposomes contaning retinoic acid at a molar ratio of 4 : 1 increased the delivery of retinoic acid about two-fold, compared with its addition as an isopropyl myristate solution. Cationic liposomes containing 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) further enhanced the incorporation dependent on the DOTAP content. Liposomes consisting of DOTAP, egg yolk PC, and retinoic acid at a molar ratio of 2 : 2 : 1 induced a 3.7-fold increase in the skin incorporation compared with the egg yolk PC liposomes without DOTAP. Significant difference was not observed when either dimyristoylphosphatidylcholine (DMPC) or dipalmitoylphosphatidylcholine (DPPC) was used instead of egg yolk PC as well as when dimethyldipalmitylammonium was used instead of DOTAP. These results suggest the potential of the use of the cationic liposomes for the intradermal delivery of lipophilic drugs like retinoic acid.