The effect of mRNA-lipid nanoparticle composition on stability during microneedle patch manufacturing

Messenger RNA (mRNA) encapsulated in lipid nanoparticles (LNPs) is a potent technology with broad applications. Microneedle patches (MNPs) can enhance the accessibility of mRNA-LNPs for vaccination or therapeutic applications. We evaluated the effects of LNP composition on the stability of mRNA-LNPs before and after MNP manufacturing, as assessed by changes in mRNA-LNP size, encapsulation efficiency, and protein expression in vitro and in vivo. The lipid molar ratio had a significant impact on LNP characteristics and ability to withstand stressors of MNP fabrication. An elevation in ionizable lipid content from 50% to 60% increased in vitro mRNA expression, measured by luciferase expression in RAW 264.7 cells, following extraction from an MNP. Among the three ionizable lipids tested, SM-102 had the highest expression before and after MNP manufacturing. Cholesterol analogues influenced in vivo expression of mRNA-LNPs before MNP manufacturing, but the effect was absent in mRNA-LNP MNPs. PEGylated lipid choice affected mRNA encapsulation in LNPs and had a strong effect on in vitro expression, but this effect was not seen in vivo. Phospholipid choice did not have a significant impact on most mRNA-LNP characteristics, but the use of DOTMA increased in vitro expression. These data suggest that LNP composition can affect mRNA-LNP characteristics and function both before and after MNP manufacturing. Future mRNA-LNP MNP designs should consider the effect of lipid molar ratios and favor higher ionizable lipid content.