Reorganization of lipid nanocapsules at air-water interface. I. Kinetics of surface film formation.

The size, the electrical properties and the behaviour at air-water interface of lipid nanocapsules (LNC) with various compositions were investigated. Two populations of LNC are presented in the suspension after the preparation: with (LNC II) and without (LNC I) phospholipid molecules. After the spreading at air-water interface, a rapid disaggregation of LNC I, located in the vicinity of interface, occurs leading to formation of surface film. The phospholipid molecules stabilize the structure of nanocapsules and LNC II are more stable at the interface in comparison with LNC I. The formation of a surface film was followed after by measuring the evolution of the surface pressure, relative surface area change and surface potential. A kinetic approach describing the various processes during the surface film formation was proposed. The corresponding kinetic constants were estimated.