Person: TOKSOY ÖNER, EBRU
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TOKSOY ÖNER
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Publication Open Access Evaluation of the Potential Use of Levan Polysaccharide in Paper Conservation(WILEY-HINDAWI, 2020-08-10) TOKSOY ÖNER, EBRU; Saglam, Rumeysa Ozen; Genc, Seval; Oner, Ebru ToksoyConservation of paper-based materials, namely, manuscripts, includes repair of tears, gap filling, consolidation, and fixation, which requires the use of adhesives. The adhesive in use for these purposes should be compatible with the chemical and physical properties of paper and should present good aging characteristics. In this study, we conducted a set of experiments with paper samples on which fructan-based biopolymer Halomonas levan (Hlevan) was applied for the first time and compared with glucan-based adhesive starch. Adhesive-applied samples were initially prepared by the application of different historical recipes of sizing and ink. Then, they underwent accelerated thermal aging. Chemical and physical changes of paper samples (crystallinity, pH, and color) were analyzed. Finally, Principal Component Analysis was performed to identify dominating factors affecting sample behavior with applied adhesives. This study demonstrates the aging characteristics of Hlevan on cellulose-based materials. The results showed that there is a color shift from blue to yellow for all samples after aging, but it is more pronounced for some samples with Hlevan. In addition, Hlevan is slightly less acidic than starch in all cases and acted as a plasticizer for a specific kind of sizing material. The methodology of this research is also efficacious in terms of understanding the interaction of paper media with the adhesives and their effects on aging.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 Open Access Polymer Based Bioadhesive Biomaterials for Medical Application-A Perspective of Redefining Healthcare System Management(MDPI, 2020-12-16) TOKSOY ÖNER, EBRU; Saha, Nibedita; Saha, Nabanita; Saha, Tomas; Toksoy Oner, Ebru; Brodnjak, Urska Vrabic; Redl, Heinz; von Byern, Janek; Saha, PetrThis article deliberates about the importance of polymer-based bioadhesive biomaterials' medical application in healthcare and in redefining healthcare management. Nowadays, the application of bioadhesion in the health sector is one of the great interests for various researchers, due to recent advances in their formulation development. Actually, this area of study is considered as an active multidisciplinary research approach, where engineers, scientists (including chemists, physicists, biologists, and medical experts), material producers and manufacturers combine their knowledge in order to provide better healthcare. Moreover, while discussing the implications of value-based healthcare, it is necessary to mention that health comprises three main domains, namely, physical, mental, and social health, which not only prioritize the quality healthcare, but also enable us to measure the outcomes of medical interventions. In addition, this conceptual article provides an understanding of the consequences of the natural or synthetic polymer-based bioadhesion of biomaterials, and its significance for redefining healthcare management as a novel approach. Furthermore, the research assumptions highlight that the quality healthcare concept has recently become a burning topic, wherein healthcare service providers, private research institutes, government authorities, public service boards, associations and academics have taken the initiative to restructure the healthcare system to create value for patients and increase their satisfaction, and lead ultimately to a healthier society.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.Publication Open Access Resveratrol-Loaded Levan Nanoparticles Produced by Electrohydrodynamic Atomization Technique(MDPI, 2021-09-30) TOKSOY ÖNER, EBRU; Cinan, Ezgi; Cesur, Sumeyye; Haskoylu, Merve Erginer; Gunduz, Oguzhan; Oner, Ebru ToksoyConsidering the significant advances in nanostructured systems in various biomedical applications and the escalating need for levan-based nanoparticles as delivery systems, this study aimed to fabricate levan nanoparticles by the electrohydrodynamic atomization (EHDA) technique. The hydrolyzed derivative of levan polysaccharide from Halomonas smyrnensis halophilic bacteria, hydrolyzed Halomonas levan (hHL), was used. Nanoparticles were obtained by optimizing the EHDA parameters and then they were characterized in terms of morphology, molecular interactions, drug release and cell culture studies. The optimized hHL and resveratrol (RS)-loaded hHL nanoparticles were monodisperse and had smooth surfaces. The particle diameter size of hHL nanoparticles was 82.06 & PLUSMN; 15.33 nm. Additionally, release of RS from the fabricated hHL nanoparticles at different pH conditions were found to follow the first-order release model and hHL with higher RS loading showed a more gradual release. In vitro biocompatibility assay with human dermal fibroblast cell lines was performed and cell behavior on coated surfaces was observed. Nanoparticles were found to be safe for healthy cells. Consequently, the fabricated hHL-based nanoparticle system may have potential use in drug delivery systems for wound healing and tissue engineering applications and surfaces could be coated with these electrosprayed particles to improve cellular interaction.