Structure–Activity-Driven Multicompartment Lipid Nanoparticles for Synergistic mRNA and siRNA Codelivery in Acute Myeloid Leukemia

The rational design of nonlamellar, multicompartment lipid nanoparticles (LNPs) offers a promising strategy for advancing nucleic acid delivery and immunotherapy. In this study, imidazole-based LNPs (A3-DM/DL-LNPs) with a mesoscopically disordered internal structure resembling the sponge phase were developed, enabling efficient codelivery of mRNA and STAT3-targeting siRNA (siSTAT3). Small-angle scattering analysis revealed a unique quasi-periodic arrangement in A3-DM/DL-LNPs, characterized by broader interdomain spacing and higher membrane heterogeneity compared to benchmark ALC-0315-LNPs, suggesting enhanced endocytosis efficiency and more favorable RNA encapsulation. The "M-shaped" polar headgroup, formed by a piperazine ring flanked by two imidazole moieties, promoted membrane interaction, cellular uptake, and transfection efficiency. In contrast, alternative LNPs with linear polar head structures (A3-SS/SM/SL-LNPs and A4-SS/SM/SL-LNPs) showed inferior delivery performance. Raman spectroscopy revealed that lipid spatial localization correlated with RNA expression in the spleen and lymph nodes, highlighting the importance of LNP structure in immune activation and targeting specific immune organs. Functionally, A3-DM/DL-LNPs restored dendritic cell (DC) antigen presentation, alleviated endoplasmic reticulum (ER) stress, and reversed T cell exhaustion in acute myeloid leukemia (AML), triggering strong immune responses and enhancing natural killer (NK) cell and T cell-mediated antileukemic activity, thereby improving therapeutic outcomes.