Adsorption of cubic liquid crystalline nanoparticles on model membranes

Abstract

The interactions of lipid based cubic liquid crystalline nanoparticles (Cubosome^®) with surface supported model membranes constituted of dioleylphosphatidylcholine (DOPC) have been studied in situ by use of ellipsometry, quartz crystal microbalance with dissipation monitoring and neutron reflectivity. The systems investigated were cubic phase dispersions of glycerol monooleate (GMO) stabilised by a non-ionic block copolymer, Pluronic^®F-127. The interaction between the cubic nanoparticles and the lipid bilayer is a dynamic process where the nanoparticles initially adsorb at the bilayer surface. Interfacial lipid exchange takes place where GMO is delivered into the bilayer and DOPC is extracted into the nanoparticle (34% loss). A subsequent release of the adsorbates can be triggered when the solution concentration exceeds 0.002 mg ml⁻¹. The release shows that the attractive interaction between the cubic nanoparticles and lipid bilayer is unstable after sufficient exchange of material takes place. This instability is indicative of a local phase separation at the interface between the bilayer and the nanoparticles, which causes desorption of nanoparticles. Some particles remain attached to the bilayer even hours after the initial interaction. The ability to trigger the release of the nanoparticles through increasing the solution concentration offers exciting potential in the design of drug delivery aids.