TY - JOUR
T1 - Calcium depletion-mediated protease inhibition and apical-junctional- complex disassembly via an EGTA-conjugated carrier for oral insulin delivery
AU - Chuang, Er-Tuan
AU - Lin, Kun Ju
AU - Su, Fang Yi
AU - Chen, Hsin Lung
AU - Maiti, Barnali
AU - Ho, Yi Cheng
AU - Yen, Tzu Chen
AU - Panda, Nilendu
AU - Sung, Hsing Wen
N1 - Funding Information:
This work was supported by a grant from the National Science Council (NSC 100-2120-M-007-003 ), Taiwan, Republic of China. The molecular-imaging study was partially supported by a grant from Chang Gung Memorial Hospital ( CMRPG391512 ).
PY - 2013
Y1 - 2013
N2 - 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.
AB - 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.
KW - Apical junctional complex
KW - Calcium depletion
KW - Chelating agent
KW - Enzyme inhibition
KW - Oral protein delivery
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U2 - 10.1016/j.jconrel.2012.11.011
DO - 10.1016/j.jconrel.2012.11.011
M3 - Article
C2 - 23195534
AN - SCOPUS:84885186250
SN - 0168-3659
VL - 169
SP - 296
EP - 305
JO - Journal of Controlled Release
JF - Journal of Controlled Release
IS - 3
ER -