Oral drug delivery vehicle for insulin and curcumin based on egg albumin-dextran conjugate: In vitro and in vivo studies

The increasing desire for oral delivery vehicle systems encouraged the development of micro and nano encapsulation technologies to protect drugs against gastric and enzymatic degradation. This study aimed to develop egg albumin-dextran conjugate as a delivery vehicle for oral administration. For this purpose, insulin was selected as a macromolecule drug and curcumin as a natural lipophilic polyphenol, both show negative absorption kinetics in gastrointestinal tract. Egg albumin-dextran conjugate was prepared by Maillard reaction under mild conditions and subsequently be used to encapsulate insulin and curcumin, respectively. The encapsulation efficiency reached to 97 % and 95.5 % at 300 mg/ml of insulin and curcumin, respectively. The profile of in vitro drug release for the insulin and curcumin indicates that approximately 60 % of the drugs were partially retained by the conjugate in gastric pH environment while a more extensive release was observed under intestinal pH conditions. Application of oral administration of insulin conjugate (IC) and/or curcumin conjugate (CC) to streptozotocin (STZ) induced diabetic rats was investigated for 6 weeks and compared with trade insulin drug. Fifty-four albino rats were separated into nine equivalent groups. Control, insulin conjugate (IC), curcumin conjugate (CC), and IC + CC. The remaining groups injected with STZ and subsequently received vehicle, IC, CC, IC + CC, and trade insulin drug; respectively. Interestingly, insulin conjugate and/or curcumin conjugate significantly reduced hyperglycemia, hyperlipidemia, decreased fructosamine level, decreased HOMA-IR, increased insulin level, increased HOMA-β, increased antioxidant defense molecules, along with modulating morphological pancreatic degeneration caused by STZ. In conclusion, oral insulin-conjugate is more effective than the trade insulin drug. Also, curcumin-conjugate has a promising role as antidiabetic agent as it may contribute in β-cells regeneration. Further, the combination between them may have synergetic antidiabetic effect. But, more detailed studies should be done to investigate the possible mechanisms of their antidiabetic effect. [Display omitted]