6Ac1-C12 is an ester-core degradable ionizable cationic lipid designed for mRNA delivery, featuring a unique hexa-acrylate ester core ("6Ac1") conjugated with six N-methyldodecylamine chains ("C12") via solvent-free Michael addition. This branched architecture enables optimal mRNA encapsulation and confers exceptional stability, maintaining consistent ~100 nm particle size for over 30 days at 4°C—crucial for cold-chain storage. With a pKa ≈ 6.0, it facilitates pH-responsive endosomal escape through membrane fusion (80% FRET signal increase at pH 5.5) and efficient cytoplasmic mRNA release.Its composition allows precise organ targeting: in conventional four-component LNPs, 98% hepatic mRNA expression occurs post-IV administration, primarily in endothelial cells (60% transfection efficiency). Cholesterol removal enables lung-specific accumulation and translation via three-component formulations, overcoming historical hepatic off-targeting. The lipid shows negligible cytotoxicity in vitro (>85% cell viability) and no significant organ damage in vivo (ALT/AST/BUN/CREA levels comparable to PBS controls). Its degradable ester core hydrolyzes into smaller metabolites, enhancing biocompatibility. Modular compatibility with DOTAP/DDAB cationic lipids expands applicability for pulmonary or splenic targeting, establishing 6Ac1-C12 as a versatile platform for organ-selective mRNA therapeutics.
