A. Delamaza et Jl. Parra, PERMEABILITY ALTERATIONS IN UNILAMELLAR LIPOSOMES DUE TO BETAINE-TYPEZWITTERIONIC AND ANIONIC SURFACTANT MIXED SYSTEMS, Journal of the American Oil Chemists' Society, 70(7), 1993, pp. 685-691
The alterations caused by betaine-type zwitterionic and anionic surfac
tant mixed systems in the permeability of unilamellar liposomes have b
een investigated. The partition coefficient of these systems, at diffe
rent molar fractions, between the aqueous phase and the lipid bilayer
of liposomes has been determined. These surfactant mixed systems were
formed by N-dodecyl-N,N-dimethylbetaine (C-12-Bet) and sodium dodecyl
sulfate (SDS) in the presence of 20 mM PIPES buffer and 110 mM Na2SO4,
at pH 7.21. Unilamellar liposomes were prepared from egg phosphatidyl
choline and phosphatidic acid (9:1 molar ratio). The release of the fl
uorescent agent 5-(6)carboxyfluorescein induced by the systems has bee
n studied at sub-solubilizing concentrations. When the molar fraction
of C-12-Bet/SDS is about 0.4, the critical micelle concentration value
s of these systems exhibit a minimum, whereas their partition coeffici
ent between the aqueous phase and lipid bilayer of lipid bilayers show
s a maximum. There is a consistent correlation between the partition c
oefficient and the ability of the different systems of surfactants to
modify the permeability of liposomes.