Atomic Force Microscopy studies of Langmuir-Blodgett Films of Lipids-Nanoparticles Mixed Systems

The study of the interaction of nanoparticles (NP) with lipid monolayers is a topic of great interest since these systems can be used as in vitro models to evaluate potential toxicological alterations, induced by nanoparticulate materials in biological relevant systems (lung surfactant, cellular membranes). Recent studies have pointed out that the presence of nanoparticles produces significant modifications in the equilibrium and mechanical properties of lipid monolayers, affecting strongly the physico-chemical physiologically relevant parameters (collapse pressure, equilibrium elasticity or linearity of the response to oscillatory deformations). These modifications are observed independently of the nanoparticles nature [1]. In this work, the structural effects of different types of nanoparticles (hydrophilic and hydrophobic silica, hydrophobic carbon black) on mixed lipid monolayers, with DPPC (Dipalmitoylphosphatidylocholine) as major component, have been investigated using Atomic Force Microscopy (AFM). For this purpose, different Langmuir-Blodgett films, deposited at different degrees of monolayers compression, have been analyzed. The results pointed out that the effect of the nanoparticles is mediated by the penetration of these to the lipid monolayers that disrupts the film structure, affecting the packing of the lipids molecules and consequently reducing the cohesion interactions in the monolayer, corroborating the results of previous studies [2, 3]. In addition to the structural characterization, preliminary essays were carried out according to the colloidal probe method, aimed at elucidating how the penetration of nanoparticles can change the adhesion properties of lipids layers and consequently some physiological functionality. References: 1. E. Guzman, L. Liggieri, E. Santini, M. Ferrari, F. Ravera, J. Phys. Chem. C 115 (2011) 21715. 2. E. Guzman, L. Liggieri, E. Santini, M. Ferrari, F. Ravera, Colloids Surf. A (2012) doi:10.1016/j.colsurfa.2011.12.059. 3. E. Guzman, L. Liggieri, E. Santini, M. Ferrari, F. Ravera, Soft Matter 8 (2012) 3938