SOLUBILIZING EFFECTS CAUSED BY THE NONIONIC SURFACTANT DODECYLMALTOSIDE IN PHOSPHATIDYLCHOLINE LIPOSOMES

The interaction of the nonionic surfactant dodecylmaltoside (DM) with phosphatidylcholine liposomes was investigated, Permeability alteratio ns were detected as a change in 5(6)-carboxyfluorescein released from the interior of vesicles and bilayer solubilization as a decrease in t he static light scattered by liposome suspensions. This surfactant sho wed higher capacity to saturate and solubilize PC liposomes and greate r affinity with these structures than those reported for the octyl glu coside, At subsolubilizing level an initial maximum in the bilayer/wat er partitioning (K) followed by an abrupt decrease of this parameter o ccurred as the effective molar ratio of surfactant to phospholipid in bilayers (Re) rose, However, at solubilizing level a direct dependence was established between both parameters, A direct correlation took pl ace in the initial interaction steps (Re up to 0.28) between the growt h of vesicles, their fluidity, and Re. A similar direct dependence was established during solubilization (Re range from 0.9 to 1.7) between the decrease in both the surfactant-PC aggregate size, the light scatt ering of the system, and Re (composition of aggregates), The fact that the free DM concentration at subsolubilizing and solubilizing levels showed values lower than and similar to its critical micelle concentra tion indicates that permeability alterations and solubilization were d etermined, respectively, by the action of surfactant monomer and by ?h e formation of mixed micelles.