Interfacial tension studies on surfactant systems at the aqueous/perfluorocarbon interface

Abstract

The effect of different phospholipid based emulsifier systems on dynamic interfacial tension at the perfluorocarbon/aqueous interface was investigated using a polytetrafluoroethylene Wilhelmy plate method. A standard phospholipid mixture composed of synthetic analogs of the major molecular species present in lecithin was formulated to represent natural egg yolk lecithin in these studies. Natural egg yolk lecithin and Pluronic F68 were studied for comparison with the standard phospholipid mixture. Analogs of the minor phospholipid species present in lecithin and other surfactant systems were investigated as additives to the standard phospholipid mixture as follows: phosphatidylinositol, phosphatidic acid, phosphatidylserine, lysophosphatidylcholine, lysophosphatidylethanolamine, cholesterol, cholesterol oleate and Pluronic F68. The perfluorocarbon/distilled water interface is a non-interacting system and therefore ideal for use in interfacial characterization of the different phospholipids and investigation of the effect of slight changes in composition on the interfacial properties of phospholipid mixtures. Low concentrations of the surfactant systems were used so that small changes in the interfacial properties could be detected on addition of the various additives. The equilibrium interfacial tension value of the standard phospholipid mixture increased on the addition of charged phospholipids; phospholipids with short fatty acyl groups and phospholipids with small head groups. The addition of Pluronic F68, lysophosphatidylcholine, lysophosphatidylethanolamine, cholesterol and cholesterol oleate to the standard phospholipid mixture resulted in lower dynamic interfacial tension values.