EFFECT OF SOME PENETRATION ENHANCERS ON EPITHELIAL MEMBRANE LIPID DOMAINS - EVIDENCE FROM FLUORESCENCE SPECTROSCOPY STUDIES

The effect of the penetration enhancers Atone, oleic acid, 1-dodecanol , dodecyl N,N-dimethylaminoacetate (DDAA), and dodecyl N,N-dimethylami noisopropionate (DDAIP) on epithelial membrane lipids was examined usi ng human buccal cell membranes as a model for epithelial lipid bilayer . Buccal epithelial cells (BEC) were labeled with 1,6-diphenyl-1,3,5-h exatriene (DPH), trimethylammonio)phenyl)-6-phenyl-1,3,5-hexatriene (T MA-DPH), and 8-anilino-1-naphthalene sulphonic acid (ANS) fluorophores to characterize enhancer-induced changes in the hydrophobic core, in the superficial polar head region, and on the exterior surface, respec tively, with fluorescence anisotropy and fluorescence lifetimes. All t he enhancers studied were found to decrease the BEC membrane lipid pac king order in a concentration-dependent and time-dependent manner in t he deep bilayer region, as shown by a 37-66% decrease in anisotropy. O leic acid was also found to disrupt membrane lipids strongly in the po lar head region, causing at least a 34% decrease in anisotropy values. Atone and DDAA were shown to alter molecular movement on the surface of the bilayers (24 and 19% decrease in anisotropy, respectively). The results suggest that interaction with membrane lipid domains is an im portant, but not the only, mode of action for the penetration enhancer s studied.