Optimization and evaluation of gastroresistant microparticles designed for siRNA oral delivery

Oral administration of siRNA is a challenging strategy for the local treatment of intestinal diseases, including cancer and inflammatory bowel disease. Both nucleic acids and delivery systems, especially lipid nanoparticles (LNPs), are sensitive to the acidic pH of the stomach, bile salts and digestive enzymes. The present work focuses on the design and evaluation of gastroresistant alginate microparticles (MPs) prepared with an original process for oral delivery of siRNA. MPs with a mean diameter of less than 200 µm were obtained without extrusion and emulsification methods. Onpattro® marketed pharmaceutical product and TNF-α siRNA-loaded LNPs were successfully microencapsulated with an efficiency of at least 80 %. Gastroresistance properties and intestinal release were demonstrated in simulated gastric and intestinal fluids. After exposure to simulated gastric fluid, MPs in contact with hepatocyte and LPS-activated monocyte-derived macrophage cell lines reduced the expression of transthyretin and TNF-α, demonstrating the preservation of the siRNA activity.