We present an efficient method for synthesizing cationic poly(ethylene imine) derivatives using the multicomponent split-Ugi reaction to create a library of functional ionizable lipopolymers. Here we show 155 polymers, formulated into polyplexes, to establish structure-activity relationships essential for endosomal escape and transfection. A lead structure is identified, and lipopolymer-lipid hybrid nanoparticles are developed to deliver mRNA to lung endothelium and immune cells, including T cells, with low in vivo toxicity. These nanoparticles show significant improvements in mRNA delivery to the lung compared to in vivo-JetPEI® and demonstrate effective delivery of therapeutic mRNA(s) of various sizes. IL-12 mRNA-loaded nanoparticles delay Lewis Lung cancer progression, while human CFTR mRNA restores CFTR protein function in CFTR knockout mice. Additionally, we demonstrate in vivo CRISPR-Cas9 mRNA delivery, achieving gene editing in lung tissue and successful PD-1 knockout in T cells in mice. These results highlight the platform's potential for systemic gene therapy delivery.
© 2025. The Author(s).

We present an efficient approach for synthesizing cationic poly(ethylene imine) derivatives using the multicomponent split-Ugi reaction to rapidly create a library of complex functional ionizable lipopolymers. We synthesized a diverse library of 155 polymers, formulated them into polyplexes to establish structure-activity relationships crucial for endosomal escape and efficient transfection. After discovering a lead structure, lipopolymer-lipid hybrid nanoparticles are introduced to preferentially deliver to and elicit effective mRNA transfection in lung endothelium and immune cells, including T cells with low in vivo toxicity. The lipopolymer-lipid hybrid nanoparticles showed 300-fold improvement in systemic mRNA delivery to the lung compared to in vivo -JetPEI ® . Lipopolymer-lipid hybrid nanoparticles demonstrated efficient delivery of mRNA-based therapeutics for treatment of two different disease models. Lewis Lung cancer progression was significantly delayed after treatment with loaded IL-12 mRNA in U155@lipids after repeated i.v. administration. Systemic delivery of human CFTR (hCFTR) mRNA resulted in production of functional form of CFTR protein in the lungs. The functionality of hCFTR protein was confirmed by restoration of CFTR- mediated chloride secretion in conductive airway epithelia in CFTR knockout mice after nasal instillation of hCFTR mRNA loaded U155@lipids. We further showed that, U155@lipids nanoparticles can deliver complex CRISPR-Cas9 based RNA cargo to the lung, achieving 5.6 ± 2.4 % gene editing in lung tissue. Moreover, we demonstrated successful PD-1 gene knockout of T cells in vivo . Our results highlight a versatile delivery platform for systemic delivering of mRNA of various sizes for gene therapy for a variety of therapeutics.