Effects of application method on skin penetration of carboxyfluorescein incorporated in liposomes.

We investigated the skin penetration of liposomes under two different application conditions; occluded and large application amount (1 ml/cm(2)), and open and small application amount (10 mul/cm(2)). Liposomes containing fluorescence-labeled phospholipids or carboxyfluorescein (CF) were used. In application under occluded conditions, phospholipids showed no penetration, even in the stratum corneum (SC). CF penetration in the skin after application of liposome was no different that after application of CF solution. In contrast, phospholipids penetrated the skin, particularly the SC and hair follicles, under open conditions. CF in liposome showed enhanced penetration in the SC and epidermis, but not in the dermis. On observation of the drying process, CF recrystallized from solution, but this did not occur with CF incorporated into liposome. It is possible that crystallization of CF is prevented by encapsulation in liposome, or that penetration occurs more readily with liposome.