Fig. 3.

Strategies for nano/microparticle-based oral vaccine delivery. a Antigens can be loaded into nano/microparticles on their surface by chemical conjugation or encapsulated inside the particles. Further, the nano/microparticle surface can be modified by conjugating different targeting ligands, such as Microfold cell and dendritic cell targeting ligands. Particles can be modified on their surface by electrostatic coating with a series of cationic and anionic polyelectrolytes or pH-sensitive polymers for enhanced stability in the gastrointestinal environment. b Approaches to enhance the permeability of particles across the intestine by targeting microfold cell (M-cells)