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

Published

August 11, 2021

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

Pub Type

Journals

Download Paper

https://doi.org/10.1038/s42003-021-02441-2

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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 January 13, 2025)