Abstract
Functionalized drug delivery systems have been investigated to improve the targetability and intracellular translocation of therapeutic drugs. We developed high functionality and quality lipids that met unique requirements, focusing on the quality of functional lipids for the preparation of targeted nanoparticles using microfluidic devices. While searching for a lipid with high solubility and dispersibility in solvents, which is one of the requirements, we noted that KK-(EK)(4)-lipid imparts nonspecific cellular association to polyethylene glycol (PEG)-modified (PEGylated) liposomes, such as cell-penetrating peptides (CPPs). We investigated whether KK-(EK)(4)-lipid, which has a near-neutral charge, is a novel CPP-modified lipid that enhances the intracellular translocation of nanoparticles. However, the cellular association mechanism of KK-(EK)(4)-lipid is unknown. Therefore, we synthesized (EK)(n)-lipid derivatives based on the sequence of KK-(EK)(4)-lipid and determined the sequence sites involved in cellular association. In addition, KK-(EK)(4)-lipid was applied to extracellular vesicles (EVs) and mRNA encapsulated lipid nanoparticles (mRNA-LNPs). KK-(EK)(4)-lipid-modified EVs and mRNA-LNPs showed higher cellular association and in vitro protein expression, respectively, compared to unmodified ones. We elucidated KK-(EK)(4)-lipid to have potential for applicability in the intracellular delivery of liposomes, EVs, and mRNA-LNPs.