Reorganization of lipid nanocapsules at air-water interface: Part 2. Properties of the formed surface film

The state, electrical and dilatational rheological properties of surface films formed at air–water interface from lipid nanocapsules (LNC) with various compositions as well as model monolayers formed by the LNC constituents—Labrafac^®, Solutol^® and Lipoid^® are investigated. These nanocapsules constitute potential drug delivery systems where lypophilic drug will be loaded in their core. The study of the model Labrafac^®/Solutol^® (Lab/Sol) mixed monolayers shows behavior close to the ideal. Small negative deviations in the mean molecular areas a and dipole moments μ are observed. All studied monolayers have elastic behavior during the small continuous compressions. The comparison between the properties of surface films formed from LNC with those of the model monolayers confirms the idea developed in the kinetic study [I. Minkov, Tz. Ivanova, I. Panaiotov, J. Proust, P. Saulnier, Reorganization of lipid nanocapsules at air–water interface: 1. Kinetics of surface film formation, J. Colloids Surf. B: Biointerfaces, submited for publication.] that the surface films formed after a rapid disaggregation of the unstable nanocapsule fraction (LNC I) contains mainly Labrafac and Solutol. The Labrafac molar part (x_Lab) in the formed Lab/Sol mixed layer is established.