Influence of cholesterol on liposome fluidity by EPR - Relationship with percutaneous absorption

The influence of liposome composition on bilayer fluidity and its effect on the percutaneous absorption into the skin were investigated. Liposomes for med with saturated or unsaturated phospholipids (H-PC or PC) with varying a mounts of cholesterol were prepared and their penetration behaviour into th e stratum corneum was followed up by means of the stripping method. The ord er and dynamics of the hydrophobic domain of the vesicles were studied usin g electron paramagnetic resonance (EPR) methodology. Phospholipid compositi on and the amount of cholesterol exert a considerable influence on the pene tration behaviour of the probe encapsulated in the liposomes. This behaviou r is closely related to the fluidity characteristics of these liposomes stu died by EPR, Therefore, a penetration mechanism of the vesicles into the sk in, based on the incorporation of lipids into the skin lipids and on fluidi ty behaviour, is suggested. (C) 2000 Elsevier Science BN. All rights reserv ed.