Ionization and structural properties of mRNA lipid nanoparticles influence expression in intramuscular and intravascular administration.

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TitleIonization and structural properties of mRNA lipid nanoparticles influence expression in intramuscular and intravascular administration.
Publication TypeJournal Article
Year of Publication2021
AuthorsCarrasco, MJ, Alishetty, S, Alameh, M-G, Said, H, Wright, L, Paige, M, Soliman, O, Weissman, D, Cleveland, TE, Grishaev, A, Buschmann, MD
JournalCommun Biol
Volume4
Issue1
Pagination956
Date Published2021 08 11
ISSN2399-3642
KeywordsAdministration, Intravenous, Animals, Drug Compounding, Gene Expression, Humans, Hydrogen-Ion Concentration, Injections, Intramuscular, Ions, Lipids, Mice, Molecular Structure, Nanoparticles, RNA, Messenger, Spectrum Analysis, Tissue Distribution, Transfection
Abstract

Lipid Nanoparticles (LNPs) are used to deliver siRNA and COVID-19 mRNA vaccines. The main factor known to determine their delivery efficiency is the pKa of the LNP containing an ionizable lipid. Herein, we report a method that can predict the LNP pKa from the structure of the ionizable lipid. We used theoretical, NMR, fluorescent-dye binding, and electrophoretic mobility methods to comprehensively measure protonation of both the ionizable lipid and the formulated LNP. The pKa of the ionizable lipid was 2-3 units higher than the pKa of the LNP primarily due to proton solvation energy differences between the LNP and aqueous medium. We exploited these results to explain a wide range of delivery efficiencies in vitro and in vivo for intramuscular (IM) and intravascular (IV) administration of different ionizable lipids at escalating ionizable lipid-to-mRNA ratios in the LNP. In addition, we determined that more negatively charged LNPs exhibit higher off-target systemic expression of mRNA in the liver following IM administration. This undesirable systemic off-target expression of mRNA-LNP vaccines could be minimized through appropriate design of the ionizable lipid and LNP.

DOI10.1038/s42003-021-02441-2
Alternate JournalCommun Biol
PubMed ID34381159