Biphasic nature of lipid bilayers assembled on silica nanoparticles and evidence for an interdigitated phase

Abstract

Functionalizing silica nanoparticles with a lipid bilayer shell is a common first step in fabricating drug delivery and biosensing devices that are further decorated with other biomolecules for a range of nanoscience applications and therapeutics. Although the molecular structure and dynamics of lipid bilayers have been thoroughly investigated on larger 100 nm–1 μm silica spheres where the lipid bilayer exhibits the typical L_α bilayer phase, the molecular organization of lipids assembled on mesoscale (4–100 nm diameter) nanoparticles is scarce. Here, DSC, TEM and ²H and ³¹P solid-state NMR are implemented to probe the organization of 1,2-dipalmitoyl-d₅₄-glycero-3-phosphocholine (DMPC-d₅₄) assembled on mesoscale silica nanoparticles illustrating a significant deviation from L_α bilayer structure due to the increasing curvature of mesoscale supports. A biphasic system is observed that exhibits a combination of high-curvature, non-lamellar and lamellar phases for mesoscale (<100 nm) supports with evidence of an interdigitated phase on the smallest diameter support (4 nm).