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

  • Commun Biol. 2021 Aug 11;4(1):956. doi: 10.1038/s42003-021-02441-2.
Manuel J Carrasco  1 ,  Suman Alishetty  1 ,  Mohamad-Gabriel Alameh  2 ,  Hooda Said  1 ,  Lacey Wright  1 ,  Mikell Paige  3 ,  Ousamah Soliman  2 ,  Drew Weissman  2 ,  Thomas E Cleveland 4th  4 ,  Alexander Grishaev  4 ,  Michael D Buschmann  5
Affiliations
  • 1. Department of Bioengineering, George Mason University, Fairfax, VA, USA.
  • 2. Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
  • 3. Department of Chemistry & Biochemistry, George Mason University, Fairfax, VA, USA.
  • 4. Institute for Bioscience and Biotechnology Research National Institute of Standards and Technology, Rockville, MD, USA.
  • 5. Department of Bioengineering, George Mason University, Fairfax, VA, USA. [email protected].
PMID: 34381159 DOI: 10.1038/s42003-021-02441-2
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.

Products