In vivo tracing of immunostimulatory raw starch microparticles after mucosal administration.

Raw starch microparticles (SMPs) proved efficient antigen carriers with adjuvant properties when administered via the mucosal route; however, the underlying mechanisms associated with this bioactivity are unknown. In the present study, we explored the mucoadhesion properties, fate, and toxicity of starch microparticles after mucosal administration. Nasally administered microparticles were mainly retained in nasal turbinates, reaching the nasal-associated lymphoid tissue; this step is facilitated by the ability of the microparticles to penetrate through the mucous epithelium. Likewise, we found intraduodenally administered SMPs on the small intestinal villi, follicle-associated epithelium, and Peyer's patches. Furthermore, under simulated gastric and intestinal pH conditions, we detected mucoadhesion between the SMPs and mucins, regardless of microparticle swelling. SMPs' mucoadhesion and translocation to mucosal immune responses induction sites explain the previously reported role of these microparticles as vaccine adjuvants and immunostimulants.