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TOKSOY ÖNER, EBRU

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TOKSOY ÖNER

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2016 - 20203
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Author: EROĞLU, MEHMET SAYIP × Subject: FILMS ×

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    Sulfated levan from Halomonas smyrnensis as a bioactive, heparin-mimetic glycan for cardiac tissue engineering applications
    (ELSEVIER SCI LTD, 2016) TOKSOY ÖNER, EBRU; Erginer, Merve; Akcay, Ayca; Coskunkan, Binnaz; Morova, Tunc; Rende, Deniz; Bucak, Seyda; Baysal, Nihat; Ozisik, Rahmi; Eroglu, Mehmet S.; Agirbasli, Mehmet; Oner, Ebru Toksoy
    Chemical derivatives of levan from Halomonas smyrnensis AAD6T with low, medium and high levels of sulfation were synthesized and characterized by FTIR and 2D-NMR. Sulfated levan samples were found to exhibit anticoagulation activity via the intrinsic pathway like heparin in a dose-dependent manner. Exceptionally high heparin equivalent activity of levan sulfate was shown to proceed via thrombin inhibition where decreased Factor Xa activity with increasing concentration was observed in antithrombin tests and above a certain concentration, levan sulfate showed a better inhibitor activity than heparin. In vitro experimental results were then verified in silico by docking studies using equilibrium structures obtained by molecular dynamic simulations and results suggested a sulfation dependent binding mechanism. With its high biocompatibility and heparin mimetic activity, levan sulfate can be considered as a suitable functional biomaterial to design biologically active, functionalized, thin films and engineered smart scaffolds for cardiac tissue engineering applications. (C) 2016 Elsevier Ltd. All rights reserved.
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    Novel levan and pNIPA temperature sensitive hydrogels for 5-ASA controlled release
    (ELSEVIER SCI LTD, 2017) TOKSOY ÖNER, EBRU; Osman, Asila; Oner, Ebru Toksoy; Eroglu, Mehmet S.
    Levan based cross-linker was successfully synthesized and used to prepare a series of more biocompatible and temperature responsive levan/N-isopropyl acrylamide (levan/pNIPA) hydrogels by redox polymerization at room temperature. Volume phase transition temperature (VPTT) of the hydrogels were precisely determined by derivative differential scanning calorimetry (DDSC). Incorporation of levan into the pNIPA hydrogel increased the VPTT from 32.8 degrees C to 35.09 degrees C, approaching to body temperature. Swelling behavior and 5-aminosalicylic acid (5-ASA) release of the hydrogels were found to vary significantly with temperature and composition. Moreover, a remarkable increase in thermal stability of levan within hydrogel with increase of pNIPA content was recorded. The biocompatibility of the hydrogels were tested against mouse fibroblast L929 cell line in phosphate buffer saline (PBS, pH 7.4). The hydrogels showed increasing biocompatibility with increasing Levan ratio, indicating levan enhanced the hydrogel surface during swelling. (C) 2017 Elsevier Ltd. All rights reserved.
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    Levan-based hydrogels for controlled release of Amphotericin B for dermal local antifungal therapy of Candidiasis
    (ELSEVIER, 2020) TOKSOY ÖNER, EBRU; Demirci, Tuba; Haskoylu, Merve Erginer; Eroglu, Mehmet Sayip; Hemberger, Jurgen; Oner, Ebru Toksoy
    Hydrogels from Halomonas levan polysaccharide were prepared at different crosslinking densities. Swelling results demonstrated pH dependent rather than temperature dependent swelling of the hydrogel and the highest swelling value was achieved at basic conditions with a swelling ratio of 9.1 +/- 0.1 which is the highest reported for levan based hydrogels. SEM images show a porous network architecture, which indicates a large surface area of the hydrogels. Rheological analyses showed the viscoelastic behavior of the hydrogels. Biocompatibility of the hydrogels was confirmed by cell culture experiments. For drug release experiments Amphotericin B (AmB) was used. 51% of the loaded AmB was released into the PBS buffer and the released AmB had a significant antifungal activity against Candida albicans.