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Ionization and Structural Properties of mRNA Lipid Nanoparticles that Influence Expression in Intramuscular and Intravascular Administration

Published

Author(s)

Manuel Carrasco, Suman Alishetty, Mohamad-Gabriel Alameh, Hooda Said, Lacey Wright, Mikell Paige, Ousamah Soliman, Drew Weissman, Thomas Cleveland, Alexander Grishaev, Michael Buschmann

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 the more negatively charged LNPs exhibit higher off-target systemic expression of mRNA in the liver following IM administration, that is undesirable for mRNA-LNP vaccines and can be minimized through appropriate design of the ionizable lipid and LNP.
Citation
Communications Biology

Keywords

mRNA, mRNA vaccines, lipid nanoparticle, ionizable lipid, pKa, zeta potential

Citation

Carrasco, M. , Alishetty, S. , Alameh, M. , Said, H. , Wright, L. , Paige, M. , Soliman, O. , Weissman, D. , Cleveland, T. , Grishaev, A. and Buschmann, M. (2021), Ionization and Structural Properties of mRNA Lipid Nanoparticles that Influence Expression in Intramuscular and Intravascular Administration, Communications Biology, [online], https://doi.org/10.1038/s42003-021-02441-2, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=932410 (Accessed April 22, 2024)
Created August 11, 2021, Updated November 29, 2022