INTERACTION BETWEEN UPOSOMES AND MONOLAYERS IN THE PRESENCE OF CALCIUM

Abstract

The interaction between phospholipid vesicles (phosphatidylcholine : phosphatide acid, 90:10 w/w) and phosphatidylcholine : cholesterol (70:30, molar ratio) monolayers at air/water interfscks has been studied at. several concentrations of calcium cation ( Ca²⁺). The liposome vesicles were SUVs and MLVS.

The vesicles interact with the monolayers, rapidly causing a large increase in surface pressure. Limiting values of surface pressure, 2.07-6.99 mN.m-1 for SUVs, and 7.01-11.11 mN.m^?1 for MLVs, were reached in less than 40?min.

Calcium ion concentration affects the liposome size in MLVs, producing an increase of gyration radius. The SUVs are little influenced. The change in size can be due to a variation of liposome composition induced by calcium: cholesterol molecules can migrate from monolayer to liposomes and the redistribution of exchanged lipids in the outer bilayer can also explain the size variation.