Chitosan-Modified Cationic Amino Acid Nanoparticles as a Novel Oral Delivery System for Insulin

In this study, chitosan-modified basic amino acid derivatives were explored as novel absorption enhancers and nanocarriers for oral insulin delivery. N-Arginine-chitosan (ACS) and N-histidine-chitosan (HCS) were successfully synthesized, and their polyelectrolyte complexes (PECs) with insulin were formed by the ordinary self-assembly method. The obtained PECs exhibited a spherical morphology with a narrow size of 205-303 nm, positive surface charge (zeta potential +14- +27 mV) and encapsulation efficiency of approximately 80%. The electrostatic interactions between chitosan derivatives and insulin were confirmed by molecular modeling simulation. In vitro studies demonstrated that PECs could partially protect insulin from proteolysis and degradation at 50 degrees C for at least 6 h. Compared with the insulin solution, internalization of PECs into Caco-2 cells was increased by up to 20.7-fold. Moreover, permeability was enhanced as the degrees of substitution of arginine and histidine increased. The PECs had in vivo pharmacological activities of 2.29%-5.39%, with a significant reduction of blood glucose levels in diabetic rats. These results suggested that ACS and HCS PECs hold promising potential for the oral delivery of insulin, peptides and proteins.