ABSTRACT
Oral delivery of proteins and peptides like insulin has remained to be elusive goal for many researchers around the world. The oral delivery of insulin is hampered by its poor gastrointestinal permeability and degradation by acidic environment in stomach and digestive enzymes in small intestine. In this study we propose a nanoparticles (NPs) composed of chitosan (CS) and poly-γ-glutamic acid (γ-PGA). The cationic NPs were prepared by simple ionic gelation between CS and γ-PGA. Further, MgSO4 and TPP were added in this formulation to increase its pH stability (pH 2.0 to pH 7.0). The loading efficiency was significantly enhanced from 3% to 50% after addition of MgSO4 and TPP. The in vitro release of insulin from aspart NPs was faster compared to regular insulin NPs because the aspart insulin was mainly present in monomer form. The native gel electrophoresis data indicated that aspart insulin did not aggregate to form hexamer in aspart NPs. TEER and transport study in caco-2 cell monolayers was used to evaluate tight junction opening ability of NPs. Confocal analysis was used to confirm the paracellular permeation of insulin. Additionally NPs were evaluated for their hypoglycemic effect in diabetic rats. Both NPs significantly reduced blood glucose; however, the aspart NPs were faster in comparison to regular insulin NPs. Similarly, the plasma insulin profiles showed that the aspart insulin was absorbed faster than regular insulin. The relative bioavailability of insulin is 12%-16%. These results indicated that oral delivery of insulin could be possible using our NPs.

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