The Langmuir technique was applied for the first time
to compare
the layers obtained by spreading lipid liquid-crystalline nanoparticles
monoolein 1-oleoyl-rac-glycerol (GMO)/Pluronic F108 cubosomes with
the monolayers obtained by mixing the same components in chloroform
at the air–water interface. The differences in the monolayer
behavior and in the acting intermolecular forces were examined. The
similarity of the isotherms obtained for the mixed components system
and the cubosome-derived layer proved the disintegration of cubosomes
into a single monolayer upon contact with the air–water interface.
Despite the low Pluronic F108 content in both types of layers, a strong
structural role of this stabilizer was also demonstrated. Cubosome-derived
systems supported on hydrophilic mica substrates were prepared either
using the combined Langmuir–Blodgett and Langmuir–Schaefer
technique or via direct adsorption from the solution. The topographies
of the obtained layers were studied by atomic force microscopy (AFM).
Images obtained in the air mode revealed the disintegration of cubosomes
and the formation of large crystallized structures of the polymer,
while AFM imaging performed in water confirmed the presence of intact
cubosomes on the surface of mica. We proved that the original structure
of cubosomes remains on one condition: the films must not dry out;
therefore, the aqueous environment must be preserved. This new approach
provides an explanation in the ongoing discussion of what happens
to lipid nanoparticles with or without cargo when they come into contact
with an interface.