Thiolated eudragit-based nanoparticles for oral insulin delivery: preparation, characterization, and evaluation using intestinal epithelial cells in vitro.

This work deals with the synthesis of insulin loaded nanoparticles (NPs) composed of thiolated Eudragit L100 (Eul-cys) and reduced glutathione (GSH) as potential nanocarriers for oral delivery of insulin. Perfectly spherical NPs with an average particle size of nearly 200-300 nm are prepared. The insulin release from Eul-cys/GSH and Eul-cys NPs in PBS (pH 7.4) shows that GSH can slightly decrease the release rate of insulin. Eul-cys in combination with GSH or sodium caprate (SC) is evaluated for its permeation enhancing effect of FITC-insulin using the Caco-2 monolayer and Caco-2/HT29-MTX co-cultured cells models. SC results in greater permeation enhancement compared to GSH. However, GSH proves to be less toxic. Paracellular transport of insulin represents the main mechanism by which the NPs facilitate insulin permeation through the intestinal epithelium, whereas a number of NPs are also taken up by the cells and release insulin within the cells.