Ionizable lipids enable lipid nanoparticles (LNPs) to deliver nucleic acids, including mRNA, to target cells. However, the efficiency of the endosomal escape of conventional LNPs remains limited to a small percentage. Lipid components that actively interact with net-neutral phospholipids in endosomal membranes and promote membrane fusion potentially enhance the efficiency of endosomal escape and further improve functional mRNA delivery. In this study, we developed a zwitterionic tri-oleoyl-Tris (zTOT) library and used it to enhance mRNA delivery by replacing the widely used helper lipid 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) in LNPs with zTOT. LNPs containing TOT-15, an example of zTOT, demonstrated a 5-fold higher gene expression compared with that of DSPC-LNPs. TOT-15-LNPs composed of commercially available ionizable lipids showed enhanced gene expression compared with that of DSPC-LNPs. The TOT-15-LNPs also showed almost 100% gene knockout efficiency with no toxicity. The TOT-15 system interacts with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and induces a non-lamellar structure. Pharmacokinetic calculation revealed that endosomal escape efficiency of the TOT-15-LNPs was more than 9.6%. In summary, the results of this study demonstrate that the zTOT system enhances the efficiency of both endosomal escape and functional mRNA delivery.
Suzuki et al. (Sun,) studied this question.