A Synergistic Effect of Select Organotin Compounds and Ionic Surfactants on Liposome Membranes

Organometallic compounds and surfactants constitute a potential threat to the environment. For that reason we have embarked on a study of their joint action on membranes. Model lecithin liposome membranes were modified with the cationic surfactant trimethyldodecylammonium bromide or the anionic surfactant sodium dodecylsulfonate, and the effect of tripropyltin chloride on the process of calcium (Ca 2+ ) and praseodymium (Pr 3+ ) desorption from the liposome membrane was studied. Kinetic constants for the process of Ca 2+ ion desorption from lecithin liposome membranes were determined using the radiotracer method. The percentage of Pr 3+ ion desorption from liposome membranes was measured by the 1 H NMR method. Trimethyltin, triethyltin and tripropyltin alone caused increased Ca 2+ and Pr 3+ desorption from liposome membranes with increasing concentration of the compounds and alkyl chain length. For both the processes studied, a cationic surfactant brought about a lower effectiveness of tripropyltin and an anionic surfactant resulted in a higher effectiveness. The effect observed can be explained by changes in the surface charge of the membrane, induced by the surfactant modifiers and by the concomitant change in the partition coefficient of the organotin. The results obtained indicate a protective or harmful joint action of the surfactants used with tripropyltin on membranes.