Inorganic Nanoparticles Challenging Lamellar and Non-Lamellar Model Membranes

Abstract

Nonlamellar lipid aqueous phases, such as reverse cubic or hexagonal phases, are ubiquitous in nature and they present a curve lipid aqueous interface on the nanoscale. The role of curvature for biomolecular interactions has been increasingly recognised. it has shown that synthetic planar lipid membranes can be used to mimic the interaction between inorganic nanoparticles (NPs) and membrane. Such studies provide relevant insights on the main factors implied in cellular trafficking and cytotoxic effects, but this type of particles are also used in nanomedicine to enhance imaging and also in therapeutic applications. The impact of NPs on curved membranes, i.e. nonlamellar phases, are much less studied. We are able to prepare lipid mesophase surface films with controlled and tuneable structure, which allows us to study the interaction of nanoparticles with lamellar and nonlamellar lipid films. The structural effects on the lipid films of gold nanoparticles (AuNPs) of different shape and surface functionalization have been studied using Neutron Reflectometry. We used spin coated layers of glycerol monooleate (GMO), forming a cubic phase, and mixtures of GMO/diphosphatidylcholine (DOPC) forming a lamellar phase. Hydrophobic and cationic particles added to the lamellar phase cause an increase in diffuse scattering, probing the presence of the particles in the film. Both the cationic and hydrophobized AuNPs seem to inserted in the cubic phase lipid film. The AuNP rods seems to perturb the lipid film structure and hydrophobic rods decrease the stability of the lipid film to a large extent. Complementary confocal microscopy imaging revealed the morphology changes of the film structure as a consequence of the particle addition. The results will be discussed in terms of particle shape and the curvature of the lipid aqueous interface.