title: Calcium depletion-mediated protease inhibition and apical-junctional-complex disassembly via an EGTA-conjugated carrier for oral insulin delivery.
abstract: Calcium (Ca(2+)) 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 Ca(2+)-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 Ca(2+) ions could be specifically chelated to the nitrogen atoms, ether oxygen atoms, and carboxylate oxygen atoms in [Ca(EGTA)](2-) anions. By chelating Ca(2+), 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 (123)I-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 hypoglycemic effect in diabetic rats. The above results confirm that this γPGA-EGTA conjugate is a promising candidate for oral insulin delivery.
authors.affiliation: Department of Chemical Engineering/Institute of Biomedical Engineering, National Tsing Hua University, Hsinchu, Taiwan, ROC.
authors.forename: Er-Yuan
authors.initials: EY
authors.lastname: Chuang
authors.forename: Kun-Ju
authors.initials: KJ
authors.lastname: Lin
authors.forename: Fang-Yi
authors.initials: FY
authors.lastname: Su
authors.forename: Hsin-Lung
authors.initials: HL
authors.lastname: Chen
authors.forename: Barnali
authors.initials: B
authors.lastname: Maiti
authors.forename: Yi-Cheng
authors.initials: YC
authors.lastname: Ho
authors.forename: Tzu-Chen
authors.initials: TC
authors.lastname: Yen
authors.forename: Nilendu
authors.initials: N
authors.lastname: Panda
authors.forename: Hsing-Wen
authors.initials: HW
authors.lastname: Sung
mesh_terms: D000284:Administration, Oral; D000818:Animals; D018938:Caco-2 Cells; D002118:Calcium / Q000378:metabolism*; D002614:Chelating Agents / Q000737:chemistry / Q000378:metabolism; D048271:Chitosan / Q000737:chemistry / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy* / Q000378:metabolism; D004337:Drug Carriers / Q000737:chemistry* / Q000378:metabolism; D004533:Egtazic Acid / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage* / Q000378:metabolism / Q000493:pharmacokinetics / Q000627:therapeutic use; D007328:Insulin / Q000008:administration & dosage* / Q000378:metabolism / Q000493:pharmacokinetics / Q000627:therapeutic use; D008958:Models, Molecular; D053758:Nanoparticles / Q000737:chemistry / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism; D011099:Polyglutamic Acid / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D002614:Chelating Agents; D004337:Drug Carriers; D007004:Hypoglycemic Agents; D007328:Insulin; C511775:poly(gamma-glutamic acid); D011099:Polyglutamic Acid; D004533:Egtazic Acid; D048271:Chitosan; D010447:Peptide Hydrolases; D002118:Calcium