A new type of lipid nanoparticles with sphingomyelin-induced active lipid raft structures for improved mRNA cellular uptake

Lipid nanoparticles (LNPs) are widely used as carriers for mRNA therapeutics. Although the safety of LNP has been significantly improved with evolvement of biodegradable ionizable lipids, the delivery efficiency still remains as a major challenge limiting the broader application of mRNA in many disease areas. Here we report a new strategy for enhancing mRNA delivery using sphingomyelin (SM) to replace DSPC and leveraging the formation of biologically active lipid raft structures with cholesterol in LNP. As a result, the novel lipid raft nanoparticles (LRNPs) formulated with an ionizable lipid, sphingomyelin (10-20 mol%), cholesterol and DMG-PEG2000 exhibited a novel "semi-lamellar" morphology which showed both electron dense and multilayer structure under cryogenic electron microscopy (Cryo-EM). The presence of lipid rafts in LRNPs was further confirmed by small-angle X-ray scattering (SAXS) data. In addition, the LRNPs exhibited significantly enhanced protein expression both in-vitro and in-vivo as compared with LNPs containing 10 mol% of DSPC. Furthermore, this enhanced therapeutic efficacy was observed in protein replacement therapy and prophylactic vaccines after intravenous and intramuscular administration, respectively. We also studied the protein corona on LRNP and found drastically different protein profiles compared to conventional LNPs, which may help to explain the improved delivery efficiency. Finally, we tested this improved delivery with different ionizable lipids such as ALC-0315 and lipid 5 in LRNP and confirmed its broad applicability. In summary, the replacement of DSPC with sphingomyelin in LNP represents an efficient approach to improve mRNA delivery in vivo and may present new opportunities for mRNA therapeutics.