Sulfonium lipid nanoparticles for intranasal mRNA delivery to lung epithelial and immune cells.

Lung epithelial and immune cells play an important role in respiratory health, serving as the first line of defense. Targeting these cells presents significant therapeutic opportunities, particularly for mRNA-based medicine. However, efficient mRNA delivery to lung cells remains challenging due to mucosal barriers, enzymatic degradation, and complex tissue architecture. In this study, we developed sulfonium lipid nanoparticles (sLNPs) featuring a sulfonium head group and branched tail structure. These sLNPs efficiently delivered mRNA to lung epithelial and immune cells via intranasal instillation in mice, transfecting club cells, ciliated cells, and macrophages, which are key players in lung structure and function. Additionally, sLNPs successfully delivered CRISPR-Cas9 mRNA and sgRNA for genome editing, as well as cytokine mRNA for immune modulation in the lungs. The sLNP platform demonstrated safety in adult mice, with no significant local or systemic tissue damage observed. These findings highlight the sLNP platform's effectiveness and versatility in delivering diverse mRNA molecules, demonstrating its potential for applications ranging from gene editing to immunomodulation therapies. With further optimization, the sLNP system could pave the way for advanced mRNA-based treatments for lung diseases. STATEMENT OF SIGNIFICANCE: Almost all of the previously developed lipids for pulmonary mRNA delivery are amine-based. We designed and synthesized a group of lipids featuring the sulfonium charge-carrying group for mRNA delivery. This is the first demonstration of employing sulfonium lipid nanoparticles (sLNPs) for mRNA delivery to lung epithelial and immune cells in vivo. These sLNPs enabled efficient pulmonary delivery of diverse mRNA cargos, supporting applications such as bioluminescence imaging, gene editing, and immunomodulation. Club and ciliated cells as well as macrophages in the bronchoalveolar fluid, were successfully transfected. No sustained inflammation or toxicity was induced, highlighting the safety of these sulfonium lipid materials.