Amphipathic lipid self-assembly on silica nanoparticle supports is relevant to the biological, analytical, and medical fields due to the importance lipid bilayer functionalization with applications in drug delivery. Lipid organization has been well characterized on silicaparticles with diameters ranging from 100 nm to 1 um. In particular, spherically supported vesicles (SSVs) have been a focus because of the stabilized lipid membrane and control of morphological structures including the induction of lipid bilayer curvature and encapsulation of small molecules for controlled release in applications for the treatment of viral, bacterial, or cancerous diseases. To understand regions of high curvature on silica nanoparticles, we combined solid-state static NMR, differential scanning calorimetry (DSC), and negative staining transmision electron microscopy (NS-TEM) to investigate the thermal properties, molecular structure and dynamics and organization of 1,2-dipalmitoyl-d54-glycero-3-phosphocholine (DMPC-d₅₄) on ultrasmall (4-100 nm) Stöber silica nanoparticles. Our ²H and ³¹P static NMR results provide evidence for greater lipid head group dynamics due to the increasing surface area and proliferation of strong interparticle interactions as the SSV sizes decrease. In addition, decreasing nanoparticle size below 100 nm exhibits an increasing presence of a biphasic system with an interdigitated cubic phase at the silica interfaces. The organization and onset of interdigitation of amphipathic lipids on SSVs reveal the dynamics of different intermediates of high curvature and should provide unique structural platforms to mimic bilayer curvature effects in a controlled way which are important for a number of biological processes including bilayer fusion events and lipid-toxin interactions.

Rich Thai

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