the invention relates to an enteric - coated capsule containing cationic nanoparticles for oral insulin delivery , in particular to a type of cationic nanoparticle including a polycationic and mucoadhesive polymer and a biodegradable polymer , wherein each of the nanoparticles has positive surface charge and enhanced permeability for paracellular insulin delivery ; the enteric - coated capsule further includes a ph - sensitive polymer as the coating . the enteric - coated capsule containing cationic nanoparticles , when being orally administered to a subject , are configured to prevent the acidic degradation of the active substance such as insulin before being released from said cationic nanoparticles to a specific absorption site along the gastrointestinal tract .