Engineered Polymeric Nanoparticles Based on Arylated Polyethylenimine Enable Spleen-Selective mRNA Delivery

Nonviral vectors hold great promise for mRNA (mRNA)-based therapeutics. However, achieving organ-selective mRNA delivery after systemic administration remains a major challenge. Herein, we engineered hydrophobized polymeric nanoparticles (PNPs) derived from arylated polyethylenimine (PEI) for efficient and organ-selective mRNA delivery. Nine new hydrophobized polymers were synthesized by grafting 2-phenylethyl acrylate (PA) onto PEI with three different molecular weights of PEI and three PA-to-PEI feeding molar ratios. The resulting PNPs were systematically evaluated for mRNA delivery both in vitro and in vivo. Through in vitro transfection screening, three optimal candidates (6PP3-PNP, 12PP6-PNP, and 24PP12-PNP) were selected for systemic mRNA delivery studies in mice. Remarkably, 6PP3-PNP preferentially delivered mRNA to the spleen, in contrast to the liver tropism observed with 12PP6-PNP and 24PP12-PNP. Moreover, 6PP3-PNP exhibited excellent biocompatibility both in vitro and in vivo. These findings elucidate the structure-function relationship of hydrophobized PEI in mRNA delivery and demonstrate a tunable strategy for developing organ-selective carriers, thereby expanding the potential of mRNA therapeutics for immunotherapy.