Two-Dimensional DPPC Based Emulsion-like Structures Stabilized by Silica Nanoparticles

Abstract

We studied the mechanical and structural properties of mixed surface layers composed by 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and silica nanoparticles (NPs). These layers are obtained by spreading a DPPC Langmuir monolayer on a colloidal silica dispersion. The transfer/incorporation of NPs into the DPPC monolayer, driven by electrostatic interactions, alters the molecular orientation, the mechanisms of domain formation, and consequently the phase behavior of the surface layer during compression. The investigation of these systems by means of complementary techniques (Langmuir trough, fluorescence microscopy, ellipsometry, and scanning electron microscopy (SEM)) shows that the incorporated NPs preferentially distribute along the liquid expanded phase of DPPC. The layer assumes the stable and homogeneous bidimensional structure of a two-dimensional (2D) analogue of a Pickering emulsion. In fact, the presence of particles provides a circular shape to the DPPC domains and stabilizes them against growth and coalescence during the monolayer compression.

Influence of Carbon Nanosheets on the Behavior of 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine Langmuir Monolayers

“…Furthermore, the chemical complexity of lung surfactant makes it necessary to reduce the number of chemical species included in the used model to deepen the role of each single component in the interfacial properties of the lung surfactant layer and to understand how nanoparticles modify its performance. The most extended model used in studies related to the interaction of lung surfactant layers with nanoparticles is the 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) [10,[25][26][27][28][29][30][31][32][33][34][35][36][37][38]. This lipid is the main component of the lung surfactant (about 40 wt% of the total weight), playing a key role in the ability of lung surfactant to decrease the surface tension until quasi-null values and in the formation of ordered monolayers with a high lateral cohesion.…”

Colloids at Fluid Interfaces

“…The appearance of a meniscus around an isotropic colloid at a flat interface makes it necessary that the colloids exert a force in the direction perpendicular to the interface. This can occur when the densities of the colloidal particles and the fluid are similar, or when the colloids and the interface present charges [69,70,76,[88][89][90][91]. In contrast, the role of capillary interactions can be considered negligible for small colloids, or when electrostatic interactions are weak.…”

Interactions of bioactive molecules & nanomaterials with Langmuir monolayers as cell membrane models

“…understanding of the effects of silica NPs on phospholipids has actually led to a subsequent study aiming at the development of innovative 2D nanostructures analogous to Pickering emulsion [268].…”