Person: TOKSOY ÖNER, EBRU
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TOKSOY ÖNER
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Publication Metadata only Synthesis and characterization of levan hydrogels and their use for resveratrol release(SAGE PUBLICATIONS LTD, 2021) TOKSOY ÖNER, EBRU; Selvi, Sinem Selvin; Haskoylu, Merve Erginer; Genc, Seval; Toksoy Oner, EbruConsidering the need for systematic studies on levan based hydrogels to widen their use in drug delivery systems and biomedical applications, this study is mainly focused on the synthesis and comprehensive characterization as well as drug release properties of hydrogels based on Halomonas levan (HL) and its chemical derivatives. For this, hydrolyzed and phosphonated HL derivatives were chemically synthesized and then cross-linked with 1,4-Butanediol diglycidyl ether (BDDE) and the obtained hydrogels were characterized in terms of their swelling, adhesivity, and rheological properties. Both native and phosphonated HL hydrogels retained their rigid gel like structure with increasing shear stress levels and tack test analysis showed superior adhesive properties of the phosphonated HL hydrogels. Moreover, hydrogels were loaded with resveratrol and entrapment and release studies as well as cell culture studies with human keratinocytes were performed. Biocompatible and adhesive features of the hydrogels confirmed their suitability for tissue engineering and drug delivery applications.Publication Metadata only Development and optimization of a novel PLGA-Levan based drug delivery system for curcumin, using a quality-by-design approach(ELSEVIER, 2019) TOKSOY ÖNER, EBRU; Bahadori, Fatemeh; Eskandari, Zahra; Ebrahimi, Nabiallah; Bostan, Muge Sennaroglu; Eroglu, Mehmet Sayip; Oner, Ebru ToksoyThis study aimed to develop a PLGA, Levan-based drug delivery system (DDS) of Curcumin using a quality-by-design (QbD) approach to reveal how formulation parameters affect the critical quality attributes (CQAs) of this DDS and to present an optimal design. First, a risk assessment was conducted to determine the impact of various process parameters on the CQAs of the DDS (i.e., average particle size, ZP, encapsulation efficiency and polydispersity index). Plackett-Burman design revealed that potential risk factors were Levan molecular weight, PLGA amount and acetone amount. Then, the optimization of the DDS was achieved through a Box-Behnken Design. The optimum formulation was prepared using low molecular weight Levan (134 kDa), 51.51 mg PLGA and 10 ml acetone. The model was validated and the optimized formulation was further characterized using different physic-chemical methods. The study resulted in the most stable NP with a spherical and uniform shape and physical stability tests indicated its stability for at least 60 days at room temperature. In conclusion, this study was an effort for developing a DDS which solubilizes Curcumin in clinically applicable concentrations.Publication Metadata only 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.Publication Metadata only 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 ToksoyHydrogels 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.Publication Metadata only Gradient multifunctional biopolymer thin film assemblies synthesized by combinatorial MAPLE(ELSEVIER SCIENCE BV, 2019) TOKSOY ÖNER, EBRU; Mihailescu, Natalia; Haskoylu, Merve Erginer; Ristoscu, Carmen; Bostan, Muge Sennaroglu; Sopronyi, Mihai; Eroglu, Mehmet S.; Chifiriuc, Mariana Carmen; Mustaciosu, Cosmin Catalin; Axente, Emanuel; Oner, Ebru Toksoy; Mihailescu, Ion N.Combinatorial Matrix-Assisted Pulsed Laser Evaporation (C-MAPLE) was recently introduced to the fast generation of compositional libraries of two biopolymers in a single-step process, for tissue engineering and regenerative medicine applications. Synchronized laser irradiation of two distinct cryogenic targets, one consisting of Sulfated Halomonas Levan and the other of quaternized low molecular weight Chitosan was used to fabricate compositional gradient coatings for surface functionalization. Synthesized coatings preserved the base material composition as confirmed by Fourier Transform Infrared Spectroscopy. Morphological study by Scanning Electron Microscopy, Atomic Force Microscopy and profilometry correlated with water contact angles measurements demonstrated that the obtained thin coatings have improved surface properties with respect to pure material coatings. Fluorescence microscopy validated the compositional gradient, while in vitro assays evidenced characteristic responses of mouse fibroblasts (L929 cell line) by distinct deposition surface regions. The coagulation test pointed out good properties for Sulfated Halomonas Levan coatings as compared to the case of an increased amount of quaternized low molecular weight Chitosan biopolymer or the control. The antimicrobial effect of the coatings was demonstrated against Escherichia coli and Staphylococcus aureus strains, representative for both Gram negative and Gram positive bacterial species, respectively, mainly involved in implant and nosocomial infections. The assembled nanostructures possess variable anti-biofilm activity along the compositional gradient, with a stronger inhibitory effect on the initial adherence phase of both tested microbial strains, but also against mature Escherichia coli biofilms. It was shown that C-MAPLE can generate discrete areas of blended polymeric composition exhibiting improved surface properties for a broad range of biomedicine applications, e.g. the fabrication of thin bioactive and cell-instructive coatings with anti-adherence properties.