Starch-based nanocapsules fabricated through layer-by-layer assembly for oral delivery of protein to lower gastrointestinal tract

Anionic carboxymethyl starch (CMS) and cationic quaternary ammonium starch (QAS), were used to fabricate nanocapsules through electrostatic layer by layer (LbL) alternate deposition onto colloidal BSA particles. An ideal starch-based colloidal nanocapsule was achieved by adjusting the degree of substitution (DS) and weight average molecular molar mass (Mw) of CMS. The nanocapsules fabricated by CMS with lower DS or Mw possessed more compact and stable core-shell structure, which favoured the BSA delivery from the upper gastrointestinal tract (GIT) to the colon. In particular, CMS/QAS nanocapsules constructed by CMS with lower DS and Mw showed better colon-specific delivery and release performance in simulated GIT fluid after 7 days' storage in different kinds of beverage (33.04%-46.35% in upper GIT, 52.70%-64.97% in colon, respectively). These findings demonstrated that CMS/QAS nanocapsules constructed by CMS with lower DS and Mw can be further exploited as a potential oral delivery system for protein to colon.