Deciphering theRole of PEGylation on the Lipid Nanoparticle-MediatedmRNA Delivery to the Liver

Organ- and cell-specific delivery of mRNA via modular lipid nanoparticles (LNPs) is promising in treating various diseases, but targeted cargo delivery is still very challenging. Most previous work focuses on screening ionizable and helper lipids to address the above issues. Here, we report the multifacial role of PEGylated lipids in manipulating LNP-mediated delivery of mRNA to the liver. We employed the typical excipients in LNP products, including DLin-MC3-DMA, DPSC, and cholesterol. Five types of PEGylated lipids were selected, and their molar ratio was fixed at 1.5% with a constant PEG molecular weight of 2000 Da. The architecture of steric lipids dramatically affected the in vitro gene transfection, in vivo blood clearance, liver deposition, and targeting of specific cells, all of which were closely linked to the de-PEGylation rate. The fast de-PEGylation resulted in short blood circulation and high accumulation in the liver. However, the ultrafast de-PEGylation enabled the deposition of more LNPs in Kupffer cells other than hepatocytes. Surprisingly, simply changing the terminal groups of PEGylated lipids from methoxyl to carboxyl or amine could dramatically increase the liver delivery of LNPs, which might be associated with the accelerated de-PEGylation rate and enhanced LNP–cell interaction. The current work highlights the importance of manipulating steric lipids in promoting mRNA delivery, offering an alternative approach for formulating and optimizing mRNA LNPs.