The interplay of quaternary ammonium lipid structure and protein corona on lung-specific mRNA delivery by selective organ targeting (SORT) nanoparticles

Messenger RNA (mRNA) can treat genetic disease using protein replacement or genome editing approaches but requires a suitable carrier to circumnavigate biological barriers and access the desired cell type within the target organ. Lipid nanoparticles (LNPs) are widely used in the clinic for mRNA delivery yet are limited in their applications due to significant hepatic accumulation because of the formation of a protein corona enriched in apolipoprotein E (ApoE). Our lab developed selective organ targeting (SORT) LNPs that incorporate a supplementary component, termed a SORT molecule, for tissue-specific mRNA delivery to the liver, spleen, and lungs of mice. Mechanistic work revealed that the biophysical class of SORT molecule added to the LNP forms a distinct protein corona that helps determine where in the body mRNA is delivered. To better understand which plasma proteins could drive tissue-specific mRNA delivery, we characterized a panel of quaternary ammonium lipids as SORT molecules to assess how chemical structure affects the organ-targeting outcomes and protein corona of lung-targeting SORT LNPs. We discovered that variations in the chemical structure of both the lipid alkyl tail and headgroup impact the potency and specificity of mRNA delivery to the lungs. Furthermore, changes to the chemical structure alter the quantities and identities of protein corona constituents in a manner that correlates with organ-targeting outcomes, with certain proteins appearing to promote lung targeting whereas others reduce delivery to off-target organs. These findings unveil a nuanced relationship between LNP chemistry and endogenous targeting, where the ensemble of proteins associated with an LNP can play various roles in determining the tissue-specificity of mRNA delivery, providing further design criteria for optimization of clinically-relevant nanoparticles for extrahepatic delivery of genetic payloads.