Rational Design of Pyrrole-Based Ionizable Lipids for mRNA Delivery

Ionizable lipids are key components of lipid nanoparticles for mRNA delivery. Inspired by the DLin-KC2-DMA ionizable lipid, we developed a series of pyrrole-based ionizable lipids to evaluate the feasibility of incorporating a rigid heterocyclic scaffold into ionizable lipid design. Systematic variation of headgroup architecture revealed that positioning the tertiary amine outside the pyrrole core substantially improved RNA encapsulation and transfection activity and identified lipid 6 as the lead structure within this series. Lipid nanoparticles formulated with lipid 6, administered via intramuscular injection, outperformed other pyrrole analogs and achieved lymph node transfection comparable to structural reference DLin-KC2-DMA. Mechanistic studies combining Förster resonance energy transfer assays and multiscale molecular dynamics simulations suggested that the improved delivery was associated with enhanced lipid-RNA electrostatic interactions and favorable membrane fusion behavior. Overall, this work establishes pyrrole as a feasible scaffold for ionizable lipid development and expands the chemical design space of mRNA delivery materials.