Novel pH-Sensitive Chitosan Nanoparticles for Oral Insulin Delivery: Mechanism, Biodistribution, Toxicological, Pharmacodynamic and Pharmacokinetic Evaluations

新穎具pH敏感性幾丁聚醣奈米微粒口服胰島素載體之機制,生物分佈,毒理學,藥物動力學及效學探討

桑傑(Kiran Sonaje)

指導教授 ： 宋信文

國立清華大學/工學院/化學工程學系/博士(2011年)

摘要

The present dissertation was aimed at evaluating the mechanism, safety and efficacy of novel pH-sensitive nanoparticles (NPs) for the oral delivery of insulin. The self-assembled NPs with pH-responsive characteristics were prepared by mixing the anionic poly-r-glutamic acid solution with the cationic chitosan (CS) solution in the presence of MgSO4 and sodium tripolyphosphate. The absorption enhancing potential of the test NPs was evaluated using an in vitro Caco-2 cell monolayer model. The in vitro results indicated that the transport of insulin across the cell monolayers was improved by NPs in a pH-dependent manner; with an increase in pH, the amount of insulin transported decreased significantly. The impact of orally administered NPs on the pharmacodynamics (PD) and pharmacokinetics (PK) of insulin was evaluated in a diabetic rat model. Oral administration of insulin-loaded NPs demonstrated a significant hypoglycemic action for at least 10 h in diabetic rats and the corresponding relative bioavailability of insulin was found to be 15.1 0.9%.
The test NPs were then used to deliver the aspart-insulin, a monomeric insulin analogue. The biodistribution of orally administered aspart-insulin via NPs was studied in rats using the single-photon emission computed tomography (SPECT)/computed tomography (CT). The results indicated that the insulin was absorbed into the systemic circulation, while the drug carrier (CS) was mainly retained in the gastrointestinal tract. The biodistribution of orally administered aspart-insulin was then compared that administered via subcutaneous (SC) injection. In the PD/PK evaluation in a diabetic rat model, the orally administered aspart-insulin-loaded NPs produced a slower hypoglycemic response for a prolonged period of time, whereas the SC injection of aspart-insulin produced a more pronounced hypoglycemic effect for a relatively shorter duration. Finally, comparison of the PD/PK profiles of the orally administered aspart-insulin with those of the SC injection of NPH-insulin (an intermediate-acting insulin preparation) suggested the suitability of our NP system as a noninvasive alternative for the basal insulin therapy.
It has been suggested that the paracellular permeation enhancement by CS may result in the absorption of unwanted toxins present in the GI tract. Therefore, the effects of test NPs on the oral absorption of lipopolysaccharide (LPS, a model toxin) were evaluated in animal models. The results indicated that the intestinal mucus layer acts as a barrier for the absorption of orally administered LPS. However, the test NPs could infiltrate the mucus layer due to their positive surfaces and were able to enhance the absorption of loaded insulin alone without affecting the absorption of LPS. Additionally, the toxicity study confirmed that test NPs did not improve the oral absorption of LPS.
Finally, the ultrastructural effects of CS on the epithelial tight junctions and paracellular permeability were investigated using transmission electron microscopy (TEM). The results indicated that the interaction of CS with intestinal cells induced a relatively rapid increase in paracellular permeability both in vitro and in vivo. The mechanism of action of CS with regard to its ability to disrupt epithelial cell TJs was found to be due to the translocation of the TJs proteins ZO-1, occludin and JAM-1 from the plasma membrane into the cytosol. The TEM results revealed no detectable alterations in the morphology of the TJs or lateral intercellular spaces, indicating that the TJ opening activity of CS was transient and reversible. These results indicated that the prepared NPs can serve as a safe and effective alternative for the oral delivery of insulin

關鍵字

幾丁聚醣奈米微粒 ； 胰島素 ； 口服釋放 ； 機制 ； 生物分布 ； 安全性

並列摘要

無資料

並列關鍵字

Chitosan nanoparticles ； Insulin ； Oral Delivery ； Mechanism ； Biodistribution and Pharmacokinetics ； Safety

參考文獻

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