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A V Pestov - One of the best experts on this subject based on the ideXlab platform.

  • chitosan gels and cryogels cross linked with diglycidyl ethers of ethylene glycol and polyethylene glycol in acidic media
    Biomacromolecules, 2019
    Co-Authors: Svetlana Atskaya, Yuliya Priva, D V Nesterov, E Modi, Mikhail I Kodess, A Slobodyuk, Dmitry Marini, A V Pestov
    Abstract:

    Here we show that the efficacy of the chitosan interaction with diglycidyl ethers of glycols significantly depends on pH and the nature of acid used to dissolve chitosan. In solutions of hydrochloric acid, cross-linking with diglycidyl ethers of ethylene glycol (EGDGE) and polyethylene glycol (PEGDGE) at room and subzero temperatures yields mechanically stable chitosan gels and cryogels, while in acetic acid solutions only weak chitosan gels can be formed under the same conditions. A combination of elemental analysis, FT-IR spectroscopy, and solid state 13C and 15N NMR spectroscopy was used to elucidate possible differences in the mechanism of chitosan cross-linking in alkaline and acidic media at room and subzero temperatures. We have proved that in acidic media diglycidyl ethers of glycols interacted with chitosan mainly via hydroxyl groups at the C6 position of the Glucosamine Unit. Besides, not only cross-linkages but also grafts were formed at room temperature. The cryo-concentration effect facilitat...

Svetlana Atskaya - One of the best experts on this subject based on the ideXlab platform.

  • chitosan gels and cryogels cross linked with diglycidyl ethers of ethylene glycol and polyethylene glycol in acidic media
    Biomacromolecules, 2019
    Co-Authors: Svetlana Atskaya, Yuliya Priva, D V Nesterov, E Modi, Mikhail I Kodess, A Slobodyuk, Dmitry Marini, A V Pestov
    Abstract:

    Here we show that the efficacy of the chitosan interaction with diglycidyl ethers of glycols significantly depends on pH and the nature of acid used to dissolve chitosan. In solutions of hydrochloric acid, cross-linking with diglycidyl ethers of ethylene glycol (EGDGE) and polyethylene glycol (PEGDGE) at room and subzero temperatures yields mechanically stable chitosan gels and cryogels, while in acetic acid solutions only weak chitosan gels can be formed under the same conditions. A combination of elemental analysis, FT-IR spectroscopy, and solid state 13C and 15N NMR spectroscopy was used to elucidate possible differences in the mechanism of chitosan cross-linking in alkaline and acidic media at room and subzero temperatures. We have proved that in acidic media diglycidyl ethers of glycols interacted with chitosan mainly via hydroxyl groups at the C6 position of the Glucosamine Unit. Besides, not only cross-linkages but also grafts were formed at room temperature. The cryo-concentration effect facilitat...

  • Chitosan Gels and Cryogels Cross-Linked with Diglycidyl Ethers of Ethylene Glycol and Polyethylene Glycol in Acidic Media
    2019
    Co-Authors: Svetlana Atskaya, Yuliya Priva, E Modi, Mikhail I Kodess, A Slobodyuk, Dmitry Marini, Denis Nesterov, Alexande Pestov
    Abstract:

    Here we show that the efficacy of the chitosan interaction with diglycidyl ethers of glycols significantly depends on pH and the nature of acid used to dissolve chitosan. In solutions of hydrochloric acid, cross-linking with diglycidyl ethers of ethylene glycol (EGDGE) and polyethylene glycol (PEGDGE) at room and subzero temperatures yields mechanically stable chitosan gels and cryogels, while in acetic acid solutions only weak chitosan gels can be formed under the same conditions. A combination of elemental analysis, FT-IR spectroscopy, and solid state 13C and 15N NMR spectroscopy was used to elucidate possible differences in the mechanism of chitosan cross-linking in alkaline and acidic media at room and subzero temperatures. We have proved that in acidic media diglycidyl ethers of glycols interacted with chitosan mainly via hydroxyl groups at the C6 position of the Glucosamine Unit. Besides, not only cross-linkages but also grafts were formed at room temperature. The cryo-concentration effect facilitates cross-linkages formation at −10 °C and, despite lower modification degrees compared to those of gels obtained at room temperature, supermacroporous chitosan cryogels with Young’s moduli up to 90 kPa can be fabricated in one step. Investigations of chitosan cryogels biocompatibility in a mouse model have shown that a moderate inflammatory reaction around the implants is accompanied by formation of a normal granulation tissue. No toxic, immunosuppressive, and sensitizing effects on the recipient’s tissues have been observed

Wei Kong - One of the best experts on this subject based on the ideXlab platform.

  • investigation into efficiency of a novel glycol chitosan bestatin conjugate to protect thymopoietin oligopeptides from enzymatic degradation
    Journal of Pharmaceutical Sciences, 2016
    Co-Authors: Yong Zhang, Jiao Feng, Lili Cui, Yuebin Zhang, Nianqiu Shi, Yan Chen, Wei Kong
    Abstract:

    Abstract In this study, a novel glycol chitosan (GCS)–bestatin conjugate was synthesized and evaluated to demonstrate its efficacy in protecting thymopoietin oligopeptides from aminopeptidase-mediated degradation. Moreover, the mechanism and relative susceptibility of three thymopoietin oligopeptides, thymocartin (TP4), thymopentin (TP5), and thymotrinan (TP3), to enzymatic degradation were investigated and compared at the molecular level. Initial investigations indicated that formation of the GCS–bestatin conjugate, with a substitution degree of 7.0% (moles of bestatin per mole of glycol Glucosamine Unit), could significantly protect all 3 peptides from aminopeptidase-mediated degradation in a concentration-dependent manner. The space hindrance and loss of one pair of hydrogen bonds, resulting from the covalent conjugation of chitosan with bestatin, did not affect the specific interaction between bestatin and aminopeptidase. Moreover, TP4 displayed a higher degradation clearance compared with those of TP5 and TP3 under the same experimental conditions. The varying levels of susceptibility of these 3 peptides to aminopeptidase (TP4 > TP5 > TP3) were closely related to differences in their binding energies to enzyme, which mainly involved Van der Waals forces and electrostatic interactions, as supported by the results of molecular dynamics simulations. These results suggest that GCS–bestatin conjugate might be useful in the delivery of thymopoietin oligopeptides by mucosal routes, and that TP3 and TP5 are better alternatives to TP4 for delivery because of their robust resistance against enzymatic degradation.

Russell E Bishop - One of the best experts on this subject based on the ideXlab platform.

  • structural biology of membrane intrinsic β barrel enzymes sentinels of the bacterial outer membrane
    Biochimica et Biophysica Acta, 2008
    Co-Authors: Russell E Bishop
    Abstract:

    The outer membranes of Gram-negative bacteria are replete with integral membrane proteins that exhibit antiparallel β-barrel structures, but very few of these proteins function as enzymes. In Escherichia coli, only three β-barrel enzymes are known to exist in the outer membrane; these are the phospholipase OMPLA, the protease OmpT, and the phospholipid∷lipid A palmitoyltransferase PagP, all of which have been characterized at the structural level. Structural details have also emerged for the outer membrane β-barrel enzyme PagL, a lipid A 3-O-deacylase from Pseudomonas aeruginosa. Lipid A can be further modified in the outer membrane by two β-barrel enzymes of unknown structure; namely, the Salmonella enterica 3′-acyloxyacyl hydrolase LpxR, and the Rhizobium leguminosarum oxidase LpxQ, which employs O2 to convert the proximal Glucosamine Unit of lipid A into 2-aminogluconate. Structural biology now indicates how β-barrel enzymes can function as sentinels that remain dormant when the outer membrane permeability barrier is intact. Host immune defenses and antibiotics that perturb this barrier can directly trigger β-barrel enzymes in the outer membrane. The ensuing adaptive responses occur instantaneously and rapidly outpace other signal transduction mechanisms that similarly function to restore the outer membrane permeability barrier. © 2007 Elsevier B.V. All rights reserved.

Yuliya Priva - One of the best experts on this subject based on the ideXlab platform.

  • chitosan gels and cryogels cross linked with diglycidyl ethers of ethylene glycol and polyethylene glycol in acidic media
    Biomacromolecules, 2019
    Co-Authors: Svetlana Atskaya, Yuliya Priva, D V Nesterov, E Modi, Mikhail I Kodess, A Slobodyuk, Dmitry Marini, A V Pestov
    Abstract:

    Here we show that the efficacy of the chitosan interaction with diglycidyl ethers of glycols significantly depends on pH and the nature of acid used to dissolve chitosan. In solutions of hydrochloric acid, cross-linking with diglycidyl ethers of ethylene glycol (EGDGE) and polyethylene glycol (PEGDGE) at room and subzero temperatures yields mechanically stable chitosan gels and cryogels, while in acetic acid solutions only weak chitosan gels can be formed under the same conditions. A combination of elemental analysis, FT-IR spectroscopy, and solid state 13C and 15N NMR spectroscopy was used to elucidate possible differences in the mechanism of chitosan cross-linking in alkaline and acidic media at room and subzero temperatures. We have proved that in acidic media diglycidyl ethers of glycols interacted with chitosan mainly via hydroxyl groups at the C6 position of the Glucosamine Unit. Besides, not only cross-linkages but also grafts were formed at room temperature. The cryo-concentration effect facilitat...

  • Chitosan Gels and Cryogels Cross-Linked with Diglycidyl Ethers of Ethylene Glycol and Polyethylene Glycol in Acidic Media
    2019
    Co-Authors: Svetlana Atskaya, Yuliya Priva, E Modi, Mikhail I Kodess, A Slobodyuk, Dmitry Marini, Denis Nesterov, Alexande Pestov
    Abstract:

    Here we show that the efficacy of the chitosan interaction with diglycidyl ethers of glycols significantly depends on pH and the nature of acid used to dissolve chitosan. In solutions of hydrochloric acid, cross-linking with diglycidyl ethers of ethylene glycol (EGDGE) and polyethylene glycol (PEGDGE) at room and subzero temperatures yields mechanically stable chitosan gels and cryogels, while in acetic acid solutions only weak chitosan gels can be formed under the same conditions. A combination of elemental analysis, FT-IR spectroscopy, and solid state 13C and 15N NMR spectroscopy was used to elucidate possible differences in the mechanism of chitosan cross-linking in alkaline and acidic media at room and subzero temperatures. We have proved that in acidic media diglycidyl ethers of glycols interacted with chitosan mainly via hydroxyl groups at the C6 position of the Glucosamine Unit. Besides, not only cross-linkages but also grafts were formed at room temperature. The cryo-concentration effect facilitates cross-linkages formation at −10 °C and, despite lower modification degrees compared to those of gels obtained at room temperature, supermacroporous chitosan cryogels with Young’s moduli up to 90 kPa can be fabricated in one step. Investigations of chitosan cryogels biocompatibility in a mouse model have shown that a moderate inflammatory reaction around the implants is accompanied by formation of a normal granulation tissue. No toxic, immunosuppressive, and sensitizing effects on the recipient’s tissues have been observed