CSL3 is a pH-switchable cationic lipid optimized for siRNA LNP delivery. Its core design features central pyridine and two ortho-methoxy groups, forming intramolecular hydrogen bonds under endosomal pH 5–6 to trigger conformational flip, which drives membrane fusion and efficient endosomal escape—an advantage absent in control lipid CSL4 without methoxy moieties. Formulated with DSPC, cholesterol and DMG-PEG2000 at a fixed molar ratio, CSL3-based LNPs achieve 85–95% siRNA encapsulation, uniform particle size and decent serum stability. In vitro tests show potent gene silencing with low cytotoxicity; in vivo intravenous administration enables obvious liver accumulation and dose-dependent Factor VII knockdown in mice, proving its great potential for hepatic RNAi therapeutic research.
