Delivery of small interfering ribonucleic acid using lipid nanoparticles prepared with pH-responsive dipeptide-conjugated lipids.

The development of lipid nanoparticles (LNPs) has enabled the clinical application of small interfering ribonucleic acid (siRNA)-based therapies. Accordingly, various unique ionizable lipids have been explored for efficient siRNA delivery. However, safety concerns related to the structure of ionizable lipids have been raised. Here, we developed a pH-responsive dipeptide-conjugated lipid (DPL) for efficient, high safety siRNA delivery. We synthesized a DPL library by varying the dipeptide sequence and established a strong correlation between the knockdown efficiency of the DPL-based LNPs and the dipeptide sequence. The LNPs prepared with a DPL containing arginine (R) and glutamic acid (E) (DPL-ER) exhibited the highest knockdown efficiency. In addition, the DPL-ER-based LNPs with relatively long lipid tails (DPL-ER-C22:C22) exhibited a higher knockdown efficiency than those with short ones (DPL-ER-18:C18). The zeta potential of the DPL-ER-C22:C22-based LNPs increased as the pH decreased from 7.4 (physiological condition) to 5.5 (endosomal condition). Importantly, the DPL-ER-C22:C22-based LNPs exhibited a higher knockdown efficiency than the LNPs prepared using commercially available ionizable lipids. These results suggest that the DPL-based LNPs are safe and efficient siRNA delivery carriers.

Increasing the siRNA knockdown efficiency of lipid nanoparticles by morphological transformation with the use of dihydrosphingomyelin as a helper lipid.

Lipid nanoparticles (LNPs), comprising ionizable lipids, helper lipids, cholesterol, and PEG lipids, can act as delivery carriers for nucleic acids and have achieved clinical success in the delivery of siRNA and mRNA. It has been shown that the morphology of LNPs varies depending on their lipid composition, but the influence of their morphology on nucleic acid efficacy has not been fully elucidated. In this study, we used our previously developed novel lipid, dioleoylglycerophosphate-diethylenediamine conjugate (DOP-DEDA), to create pH-responsive LNPs (DOP-DEDA LNPs). We evaluated the morphology of DOP-DEDA LNPs composed of different helper lipids and the knockdown efficiency of small interfering RNA (siRNA). A distinctive difference in morphology was observed between DOP-DEDA LNPs of different helper lipids. Significant differences were also observed in the apparent pKa of DOP-DEDA LNPs and the knockdown efficiency of siRNA, which may be due to the difference in the localization of DOP-DEDA molecules in DOP-DEDA LNPs. These findings suggest that changing helper lipids alters the morphology of the DOP-DEDA LNP system, which affects the apparent pKa and knockdown efficiency of siRNA.