Interactions between nano-ions and a lipid monolayer: Nano-structural insights from NR

Nano-ions have recently attracted increasing interest due to their fascinating properties. Nano-ions such as polyoxometalates (POMs), boron clusters and hydrophobic ions, are nanometric ionic molecules with unique architecture and super-chaotropic properties. They have promising antitumor, anti-infectious and anti-Alzheimer’s activities. Despite nano-ions promising membrane-targeting ability, direct evidence for the proposed mechanism based on the formation and desorption of POM-lipid assemblies is lacking. Their interactions with cell membranes, relevant to their cytotoxicity and drug delivery applications, remain poorly understood. Our recent trial results from XRR experiment at ESRF BM28 showed that mixed 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/ 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) vesicles ruptured on mica surface to form lipid bilayers (SLBs). The Kiessig fringes of SLBs become more pronounced with increasing temperature. The addition of nano-ions to SLBs resulted in structural changes, which depend on the type of the nano-ion used. Here, we propose a complementary neutron reflectivity (NR) study of the effects of nano-ions on the lipid monolayer at the air-water interface on an LB trough, as a function of lipid composition, type of nano-ions, concentrations, surface pressure, and temperature.