A Combinatorial Library of Lipid Nanoparticles for Cell Type-Specific mRNA Delivery

Lipid nanoparticles (LNPs) are the most advanced non-viral drug delivery systems for various mRNA therapeutics and vaccines. Despite the recent and rapid progress in LNP-based mRNA therapeutics, delivery of mRNA remains the primary hindrance preventing the development of novel therapeutic modalities. Specifically, cell type-specific, extra-hepatic mRNA delivery is still a major hurdle due to the lack of efficient delivery systems. Herein, we synthesized a novel ionizable lipid library with hydroxylamine or ethanolamine linkers by modifying hydrophobic tails. Stable LNPs were prepared by utilizing microfluidic mixing of these lipids with other lipids and mRNA. Using vigorous screening in vitro and in vivo, superior LNPs formulations were identified for cell-type specific mRNA delivery. Our in vitro assays denote that the branched ester tail negatively affects mRNA delivery efficiency when coupled with a hydroxylamine linker. In vivo studies identify Lipid 23 as a liver-trophic, superior mRNA delivery lipid and Lipid 16 as a cell type-specific ionizable lipid for CD11bhi macrophage-targeted population, without an additional targeting moiety. Overall, our study suggests that the novel functionality of ionizable lipids is derived from the combination of tail and linker, especially for developing cell type-specific mRNA delivery, and might open new therapeutic modalities utilizing these novel ionizable lipids.