Imidazolium Lipid-based Nanoparticles Enable Effective mRNA Delivery and Cellular Immune Response

Imidazolium LipidBrick^® cationic lipid nanoparticles (LNPs) provide a pH-independent alternative to conventional ionizable systems for nucleic acid delivery. Through a high-throughput screen of 1,944 formulations spanning eight imidazolium cores, three helper lipids, and varying PEG densities, we found that more than half of the library outperformed the clinical ionizable benchmark ALC-0315 in multiple representative mammalian cell types. Top-performing candidates showed robust cellular uptake, efficient endosomal escape, and strong transgene expression both in vitro and following intramuscular administration. A lead formulation (C3 LNP), incorporating an imidazolium lipid core bearing a hydroxyethyl substituent, with 30 mol% DOPE, achieved comparable intramuscular luciferase expression and antibody titers to ALC-0315, while eliciting ~3-fold stronger ovalbumin-specific IFN-γ⁺ T-cell responses and maintaining low cytotoxicity. Machine-learning analysis of the dataset further distilled transferable design rules to inform future formulation strategies. Collectively, these findings establish cationic LipidBrick^® LNPs as a versatile platform for mRNA delivery, offering a generalizable framework for the high-throughput discovery of ionization-independent systems that effectively prime adaptive immune responses.