Eudragit-Coated Lipid Nanoparticles for Oral Administration and In Vivo Gene Expression in the Gastrointestinal Tract

Background: Lipid nanoparticle (LNP) systems have emerged as leading platforms for nucleic acid delivery, with high transfection, biocompatibility, and clinical success in RNA therapeutics. However, oral nucleic acid delivery remains a major challenge, as nucleic acids and LNPs are highly susceptible to degradation under gastrointestinal (GI) conditions, which includes acidic pH, digestive enzymes, and bile salts. To address these limitations, we developed Eudragit® S 100-coated lipid nanoparticles (Eu-LNPs) as a pH-responsive system for oral nucleic acid delivery. Methods: We optimized LNPs formulated with the ionizable lipid SM-102, with and without Eu coating, by varying the nitrogen-to-phosphate (N/P) ratio, and evaluated them in vitro and in vivo. Results: Increasing the N/P ratio (3–10) significantly improved encapsulation, with N/P 10 achieving the highest nucleic acid loading while slightly reducing particle size and maintaining low polydispersity. Using a model luciferase-expressing mRNA, SM-102-based LNPs exhibited strong transfection in HEK-293 cells, with the highest luminescence-to-viability ratio observed at N/P 6. Similarly, using a GFP-expressing mRNA, strong GFP fluorescence was also observed in HEK-293, SW480, and RAW 264.7 cells, confirming efficient intracellular delivery. Subsequently, we coated the LNPs with Eudragit® S 100 to form Eu-LNPs. The coated nanoparticles preserved the encapsulated mRNA integrity for up to 7 days at 4 °C. In vivo studies in C57BL/6 mice showed that orally administered eGFP mRNA-loaded Eu-LNPs increased GFP fluorescence signal throughout the GI tract, whereas uncoated LNPs showed a negligible difference in fluorescence compared to the control. Conclusions: Overall, this study demonstrates that Eudragit® S 100-coated LNPs represent a promising approach for oral RNA delivery to the GI tract.