A modular polymer platform for efficient mRNA delivery in cancer immunotherapy

The use of mRNA for prophylactic and therapeutic applications, such as treating coronavirus and cancer, has garnered significant attention. However, owing to the inherent labile nature of mRNA, it requires robust delivery platforms to enable effective mRNA-based therapies. While lipid nanoparticles (LNPs) have shown success in mRNA delivery, they face challenges in terms of safety, storage and manufacturing costs. Polymeric mRNA delivery platforms have emerged as promising alternatives due to their structural versatility, durability, and transfection efficiency. This study presents PFHA-PEI-mRNA-HP, a polymeric mRNA delivery nanoplatform that utilizes simultaneous fluorination and heparinization of low molecular weight polyethylenimine (PEI)-based mRNA complexes to enhance performance. These modifications applied to the PEI backbone significantly improved the physicochemical properties, cellular uptake, endosomal escape capability, and biocompatibility of the platform, resulting in a substantial increase in transfection efficiency. PFHA-PEI-mRNA-HP achieved ultra-high transfection efficiency of >90% across multiple cancer cell types, outperforming the LNP-based delivery reagent Lipofectamine 2000. Additionally, PFHA-PEI-mRNA-HP demonstrated superior stability compared to Lipofectamine 2000 when stored above 0 °C for 15 days. When loaded with therapeutic IL12 mRNA, PFHA-PEI-mRNA-HP effectively delivered its payload <i>in vivo</i> and, in combination with anti-PD-L1 therapy, significantly inhibited tumor growth in a triple-negative breast cancer mouse model without causing harm to healthy tissues. These results highlight PFHA-PEI-mRNA-HP as a highly efficient and reliable mRNA delivery platform for cancer gene therapies.