Nanoscale dynamics of self-assembled lipid nanoparticles via SANS

The nano-scale dynamics of lipid nanoparticles (LNPs) for drug delivery play a large role in their function. Limited molecular motion is important for avoiding degradation prior to entering cells. Intracellularly, enhanced molecular motion is then vital for effective endosomal escape. As a self-assembled structure of four distinct lipid-based components and a nucleic acid cargo driven by both electrostatic and hydrophobic interactions, the system complexities make analysis of dynamics difficult. We experimentally quantify LNP nano-scale dynamics through time-resolved small-angle neutron scattering (TR-SANS). This technique, previously leveraged only for simpler systems, provides unprecedented insight to molecular behavior of LNPs. We find, using TR-SANS in combination with traditional SANS and small-angle x-ray scattering (SAXS), that as pH drops, internal structure and molecular exchange of cholesterol change. The results provide a quantifiable metric by which to compare formulations. Successful analysis of this complex system also expands the opportunities for using TR-SANS to characterize molecular exchange in other multi-component macromolecular systems.