Investigating a model lipid nanoparticle release system with 2H NMR and SAXS

Lipid Nanoparticles (LNPs) are an attractive way of delivering of short interfering RNA (siRNA) for cancer therapeutics. Their release method relies on protonation of an ionisable amino-lipid (XTC2) in acidic endosomes. Hypothetically, the protonated XTC2 and anionic lipids in endosomal membranes interact to form non-lamellar phases, releasing the siRNA. In this project, a model release system consisting of XTC2 and anionic distearoylphosphatidylserine (DSPS-d70) at pH 4.7 was investigated with deuterium nuclear magnetic resonance (2H NMR) and small angle x-ray scattering (SAXS) to determine the lipid phases which form as a function of temperature and their structural parameters. Since cholesterol is an important structural component in LNPs, increasing amounts of cholesterol were added to the system to determine its effect. Non-lamellar phases were observed for each sample particularly at high-temperatures, though interestingly the specific phase observed by each technique was not always in complete agreement.