Enhanced stability of oral insulin in targeted peptide ligand trimethyl chitosan nanoparticles against trypsin

Oral insulin delivery is often limited by protease degradation. 2-(Dimethylamino)-2-oxoethyl 4-(4-guanidinobenzoyloxy)phenylacetate methanesulphonate (Camostat mesylate) is reported to have the ability to inhibit trypsin activity, which is the main protease responsible for protein degradation. This study attempted to form a novel nanoparticle by covalently conjugating 4-(2-(2-aminoethylamino)-2-oxoethyl)phenyl 4-guanidinobenzoyloxy (FOY-251), an active derivative of camostat mesylate, to the backbone of poly (γ-glutamic acid) (γ-PGA), in order to improve insulin stability against protease. Goblet cell targeting CSKSSDYQC (CSK) peptide was demonstrated to effectively improve the epithelial absorption of insulin. Therefore, the novel nanoparticle was prepared by mixing cationic peptide modified trimethyl chitosan (TMC-CSK) with anionic γPGA-FOY conjugate using multi-ion crosslinked method. Results showed that not only the γPGA-FOY conjugate but also the prepared novel nanoparticle could inhibit trypsin activity both in vitro environment and on the intestinal mucosal surface. This study would be beneficial for peptide modified nanoparticles in oral insulin delivery.