Structure–Function Correlation of Clinically Inspired Lipid Nanoparticles for Lung and Spleen Targeted mRNA Delivery

Lipid nanoparticles (LNPs) have emerged as a transformative platform for mRNA delivery. However, challenges such as low endosomal escape efficiency remain key barriers in the field. Herein, we systematically investigate the clinically approved COVID‐19 vaccine LNPs, extracting insights into physicochemical property‐biological function relationships. Then we apply rational design principles to use monoolein (MO) as a structural helper lipid to replace phospholipid in Moderna LNP formulations. We reveal that MO incorporation induces pH‐dependent mesophase transitions within LNPs with a protein corona, promoting inverse hexagonal mesophase structures that facilitate enhanced mRNA release and transfection. Comparison with COVID‐19 vaccine LNPs confirms that MO‐based LNPs achieve superior mRNA transfection efficiency across diverse cell types, including lung macrophages, epithelial cells, and cancer cells. Furthermore, in vivo studies validate enhanced mRNA expression of MO‐based LNPs compared to the original Moderna LNPs, underscoring the capacity of both targeted pulmonary delivery by intranasal administration and targeted spleen delivery by intravenous administration. This study establishes a definitive physicochemical structure‐biological function property correlation in LNP‐mediated mRNA delivery, with the consideration of the protein corona effect on acidification‐induced LNP internal mesophase evolution. This work provides guidance for the development of next‐generation LNP platforms based on molecular biomedical engineering design principles.