Triazole-Engineered Ionizable Lipids with Tunable Headgroups for Efficient mRNA Delivery and Protective Immunity

Abstract Lipid nanoparticles (LNPs) have emerged as a revolutionary nonviral platform for administering a wide range of therapeutics, especially nucleic acids. Expanding the diversity of lipid structures, which includes a variety of headgroups, linkers, and tail structures, offers exciting possibilities for developing novel lipid-based drug delivery systems. Consequently, the scientific community laid a greater emphasis on combinatorial methodologies for designing different libraries of ionizable lipid molecules. Herein, we are proposing the synthesis of a library of triazole-based ionizable lipids by using alkyne-azide click chemistry. Systematic variation of the terminal headgroup produced distinct mRNA expression profiles despite broadly comparable encapsulation efficiencies and physicochemical properties. LNP formulated using CL-3, containing primary amine headgroup, exhibited the highest in vitro mRNA expression and outperformed the benchmark ionizable lipids ALC-0315 and SM-102 under the conditions tested. CL-3-based LNPs elicited the highest binding-antibody titers among the evaluated formulations, while pseudovirus-neutralizing activity was comparable to that of the ALC-0315 benchmark. The immunized animals were protected in the mouse viral-challenge model under the conditions investigated. These findings identify CL-3 as a promising candidate within the evaluated lipid series and demonstrate the utility of modular synthesis for investigating structure–activity trends in mRNA delivery.