Synthesis of CSK-DEX-PLGA Nanoparticles for the Oral Delivery of Exenatide to Improve Its Mucus Penetration and Intestinal Absorption

The oral absorption of exenatide, a drug for type 2 diabetes treatment, can be improved by using nanoparticles (NPs) for its delivery. To improve the mucus penetration and intestinal absorption of exenatide, we designed a block copolymer, CSKSSDYQC-dextran-poly(lactic-co-glycolic acid) (CSK-DEX-PLGA), and used it for the preparation of exenatide-loaded NPs. The functionalized exenatide-loaded NPs composed of CSK-DEX-PLGA were able to target intestinal epithelial cells and reduce the mucus-blocking effect of the intestine. Moreover, the CSK modification of DEX-PLGA was found to significantly promote the absorption efficiency of NPs in the small intestine based on in vitro ligation of the intestinal rings and an examination of different intestinal absorption sites. Compared to DEX-PLGA-NPs (DPs), the absorption of CSK-DEX-PLGA-NPs (CDPs) was increased in the villi, allowing the drug to act on gobletlike Caco-2 cells through clathrin-, caveolin-, and gap-mediated endocytosis. Furthermore, the enhanced transport ability of CDPs was observed in a study on Caco-2/HT-29-MTX cocultured cells. CDPs exhibited a prolonged hypoglycemic response with a relative bioavailability of 9.2% in diabetic rats after oral administration. In conclusion, CDPs can target small intestinal goblet cells and have a beneficial effect on the oral administration of macromolecular peptides as a nanometer-sized carrier.