HCQ-4 is a rationally engineered ionizable lipid derived from hydroxychloroquine (HCQ), featuring a ditetradecylamine-derived twin-C14 saturated hydrocarbon tail linked to the HCQ headgroup via a succinic acid spacer. Synthesized through a three-step route involving HCQ deprotonation, ditetradecylamine carboxylation, and EDC/DMAP-mediated amidation, this lipid forms the core of optimized lipid nanoparticles (LNPs) at a molar ratio of 60:10:40:0.5 (HCQ-4:DOPE:cholesterol:DMG PEG2000). The structure enables dual functionality: (1) Spleen-selective mRNA delivery (2.3-fold higher splenic vs. hepatic transfection) via 80-100 nm particle size, near-neutral charge (-3 mV), and low PEG density, facilitating immune cell uptake; (2) Tumor microenvironment modulation through HCQ-mediated repolarization of M2 macrophages to antitumor M1 phenotype (iNOS+ cells ↑2.5-fold, CD206+ cells ↓60%). This bifunctional design synergistically enhances mRNA cancer vaccine efficacy, demonstrating superior prophylactic/therapeutic antitumor activity and antimetastatic effects compared to clinical benchmarks like MC-3 LNP.
