Replacing PEG-Lipid with Amphiphilic Polycarbonates in mRNA-Loaded Lipid Nanoparticles: Impact of Polycarbonate Structure on Physicochemical and Transfection Properties.

Since the remarkable breakthrough of COVID-19 mRNA vaccines, lipid nanoparticles (LNPs) have gained substantial attention as the most cutting-edge clinical formulations for mRNA delivery. PEGylated lipid (PEG-lipid) has been regarded as an essential constituent of LNPs that helps to prolong their systemic circulation by preventing particle aggregation in the blood and sequestration by the mononuclear phagocyte system. Herein, we synthesized a series of mRNA-loaded nanoparticles by replacing ALC-0159 (a PEG-lipid used in the Comirnaty formulation) with amphiphilic PEG-polycarbonate diblock copolymers (PC-HNPs). Interestingly, variations of polycarbonate block length and structure significantly influenced mRNA encapsulation efficiency, transfection potency, colloidal stability, and PEG shedding rate of PC-HNPs. In vivo and ex vivo bioluminescence imaging revealed that upon subcutaneous administration in mice, the leading candidate PC3-HNP achieved lymph node accumulation comparable to that of the conventional ALC-0159-based LNP formulation while avoiding undesirable liver accumulation. Our findings may provide valuable information for the construction of next-generation nanocarriers for effective mRNA delivery.