Highly Branched Poly(β-amino ester)s for Efficient mRNA Delivery and Nebulization Treatment of Silicosis.

mRNA therapeutics hold tremendous promise for disease prevention and treatment. Development of high-performance mRNA delivery systems with enhanced transfection efficiency and a safety profile will further fulfill their therapeutic potential and expedite their translation. The synthesis of "four-in-one" highly branched poly(β-amino ester)s (O-LhPAEs) is reported by integrating the essential components of lipid nanoparticles (LNPs) for spleen-selective mRNA enrichment and nebulization treatment of silicosis. 60 O-LhPAEs with distinct branched structure and chemical composition, including tertiary/quaternary amines, cholesterol moieties, zwitterionic species, and hydrophobic alkyl tails, are synthesized using sequential Michael addition, ring-opening, and nucleophilic substitution reactions. The unique topological structure and chemical composition collectively enhanced O-LhPAEs/mRNA polyplex serum resistance, cellular uptake, and endosomal escape. The optimal O-LhPAE, 20%b-3C-2P12, exhibits up to 93.1% mRNA transfection across 11 different cell types, including epithelial cells, fibroblasts, cancer cells, stem cells, neurological cells, and astrocytes. Biodistribution study reveals that 20%b-3C-2P12/mRNA polyplexes are mainly enriched in the spleen following systemic administration. Through nebulization, 20%b-3C-2P12 mediated high Tbx2 mRNA expression in the lungs of silicosis mice, effectively restoring lung functions. This study not only establishes a strategy for development of LNP-like O-LhPAEs but also provides promising candidates for highly safe, efficient, and spleen-selective mRNA delivery and nebulization treatment of silicosis.