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

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 mu m silica spheres where the lipid bilayer exhibits the typical L-alpha bilayer phase, the molecular organization of lipids assembled on mesoscale (4-100 nm diameter) nanoparticles is scarce. Here, DSC, TEM and H-2 and P-31 solid-state NMR are implemented to probe the organization of 1,2-dipalmitoyl-d(54)-glycero-3-phosphocholine (DMPC-d(54)) assembled on mesoscale silica nanoparticles illustrating a significant deviation from L-alpha 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).