Influence of lipid composition of messenger RNA-loaded lipid nanoparticles on the protein expression via intratracheal administration in mice.

Intratracheal (i.t.) administration, which takes advantage of the specific structure of the respiratory system, can effectively deliver nanoparticles to the lung. Much remains unknown about the i.t. administration of messenger RNA (mRNA)-lipid nanoparticles (LNPs) and the effect of lipid composition. In this study, we administered minute amounts of mRNA-LNP solutions into mice intratracheally and investigated the effect of lipid composition on protein expression in the lungs. We first validated higher protein expression with mRNA-LNP compared to that with mRNA-PEI complex and naked mRNA. Then, we evaluated the influence of lipid composition of LNPs on the protein expression and found that: 1) decreasing the PEG molarity from 1.5% to 0.5% could significantly increase the protein expression; 2) replacing DMG-PEG with DSG-PEG could slightly increase the protein expression; 3) using DOPE instead of DSPC could increase protein expression by an order of magnitude. We successfully prepared an mRNA-LNP with optimal lipid compositions that led to robust protein expression following i.t. administration, thus providing meaningful insights into advanced development of mRNA-LNPs for therapeutic i.t. administration.

Synthesis and evaluation of a novel adapter lipid derivative for preparation of cyclic peptide-modified PEGylated liposomes: Application of cyclic RGD peptide.

Peptide ligand modified nanoparticles can simply prepared by post-insertion method to mix pre-formed nanoparticles with peptide-lipid conjugates in an aqueous solution at an optimal temperature. Therefore, water dispersibility of peptide-lipid conjugates is a very important factor for implementing the post-insertion method. We proposed that highly water dispersible peptide-lipid conjugates can be easily synthesized by separately designing novel adapter lipids with different water dispersibility and reacting them with ligands in a highly efficient manner. Adapter lipids have three critical roles; as spacers of ligand-conjugated lipids for efficient ligand presentation, as structures that form discrete molecular weight distributions, and as providing water dispersibility. In this study, we developed a novel adapter-lipid derivative that enables a variety of cyclic peptide modifications using the click reaction. The integrin αvß3-targeted cyclic RGDfK (cRGD) peptide was selected as the cyclic peptide ligand. We designed a novel alkyne-tagged lipid with a discrete peptide spacer and bound the cRGD peptide using a click reaction to synthesize a cRGD-conjugated lipid with good water dispersibility for the preparation of cRGD-modified PEGylated liposomes using the post-insertion method. We also revealed that cRGD-modified PEGylated liposomes are efficiently associated with integrin αvß3-expressing murine colon carcinoma (Colon-26) cells in a modification amount- and peptide sequence-dependent manner, showing high cytotoxicity upon loading with doxorubicin. This novel adapter lipid derivative can be used to synthesize various cyclic peptides by click reactions and will provide useful insights for the future development of cyclic peptide-modified PEGylated liposomes.