THE ALTERATION OF PERMEABILITY OF SMALL UNILAMELLAR LIPOSOMES BY AMPHOTERIC ALKYLBETAINE SURFACTANTS

The partition coefficients have been determined for a series of amphoteric alkyl betaine surfactants (alkyl chain lengths C-10, C-12, and C-14), partitioning between the aqueous phase and the lipid bilayer of small unilamellar vesicle liposomes (SUV) made from egg phosphatidylcholine and phosphatidic acid (9:1 molar ratio). The release of the fluorescent agent 5-(6)carboxyfluorescein, induced by the surfactants, was studied at sub-solubilizing concentrations. The following order of the partition coefficients was obtained for the surfactants: tetradecylbetaine > dodecylbetaine > decylbetaine. There was a strong correlation between the partition coefficient and the ability of the different surfactants to modify the permeability of liposomes.