Calcium depletion-mediated protease inhibition and apical-junctional- complex disassembly via an EGTA-conjugated carrier for oral insulin delivery

Er-Tuan Chuang, Kun Ju Lin, Fang Yi Su, Hsin Lung Chen, Barnali Maiti, Yi Cheng Ho, Tzu Chen Yen, Nilendu Panda, Hsing Wen Sung

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40 Citations (Scopus)


Calcium (Ca2+) has a crucial role in maintaining the intestinal protease activity and in forming the apical junctional complex (AJC) that preserves epithelial barrier function. Ethylene glycol tetraacetic acid (EGTA) is a Ca2+-specific chelating agent. To maintain the concentration of this chelator in areas where enzyme inhibition and paracellular permeation enhancement are needed, this study synthesized a poly(γ-glutamic acid)-EGTA conjugate (γPGA-EGTA) to form nanoparticles (NPs) with chitosan (CS) for oral insulin delivery. The results of our molecular dynamic (MD) simulations indicate that Ca2+ ions could be specifically chelated to the nitrogen atoms, ether oxygen atoms, and carboxylate oxygen atoms in [Ca(EGTA)]2- anions. By che-lating Ca2+, γPGA-EGTA conferred a significant insulin protection effect against proteases in intestinal tracts isolated from rats. Additionally, calcium depletion by γPGA-EGTA could stimulate the endocytosis of AJC components in Caco-2 cell monolayers, which led to a reversible opening of AJCs and thus increased their paracellular permeability. Single-photon emission computed tomography images performed in the biodistribution study clearly show the 123I-insulin orally delivered by CS/γPGA-EGTA NPs in the heart, aorta, renal cortex, renal pelvis and liver, which ultimately produced a significant and prolonged hypoglyce-mic effect in diabetic rats. The above results confirm that this γPGA-EGTA conjugate is a promising candidate for oral insulin delivery.

Original languageEnglish
Pages (from-to)296-305
Number of pages10
JournalJournal of Controlled Release
Issue number3
Publication statusPublished - 2013
Externally publishedYes



  • Apical junctional complex
  • Calcium depletion
  • Chelating agent
  • Enzyme inhibition
  • Oral protein delivery

ASJC Scopus subject areas

  • Pharmaceutical Science

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