Materials Science and Engineering / Malzeme Bilimi ve Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4719
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Article Citation - WoS: 61Citation - Scopus: 64Electrospun Gelma Fibers and P(hema) Matrix Composite for Corneal Tissue Engineering(Elsevier Ltd., 2021) Arıca, Tuğçe A.; Güzelgülgen, Meltem; Yıldız, Ahu Arslan; Demir, Mustafa MuammerThe development of biocompatible and transparent three-dimensional materials is desirable for corneal tissue engineering. Inspired from the cornea structure, gelatin methacryloyl-poly(2-hydroxymethyl methacrylate) (GelMA-p(HEMA)) composite hydrogel was fabricated. GelMA fibers were produced via electrospinning and covered with a thin layer of p(HEMA) in the presence of N,N?-methylenebisacrylamide (MBA) as cross-linker by drop-casting. The structure of resulting GelMA-p(HEMA) composite was characterized by spectrophotometry, microscopy, and swelling studies. Biocompatibility and biological properties of the both p(HEMA) and GelMA-p(HEMA) composite have been investigated by 3D cell culture, red blood cell hemolysis, and protein adsorption studies (i.e., human serum albumin, human immunoglobulin and egg white lysozyme). The optical transmittance of the GelMA-p(HEMA) composite was found to be approximately 70% at 550 nm. The GelMA-p(HEMA) composite was biocompatible with tear fluid proteins and convenient for cell adhesion and growth. Thus, as prepared hydrogel composite may find extensive applications in future for the development of corneal tissue engineering as well as preparation of stroma of the corneal material. © 2020 Elsevier B.V.Article Citation - WoS: 14Citation - Scopus: 17Spectrophotometric Characterization of Plasticizer Migration in Poly(vinyl Chloride)-Based Artificial Leather(Elsevier Ltd., 2021) Akkuş Altındağ, İffet; Akdoğan, YaşarPlasticized polyvinyl chloride (PVC) is one of the most commonly used material in the manufacture of artificial leather because of its flexibility, high durability and low cost. While hundreds of plasticizers have been produced to obtain PVC films and artificial leathers, it is important to choose the correct plasticizer to produce the desired products. Therefore, here five non-phthalate type plasticizers with three levels (40 phr, 60 phr and 80 phr); trioctyl trimelliate (TOTM), tributyl trimelliate (TBTM), dioctyl terephthalate (DOTP), dioctyl adipate (DOA) and dioctyl succinate (BIO) were used to prepare plasticized PVC films. They were studied in terms of their compabilities with PVC polymer chains, and their effects on mechanical properties of PVC films. Although, linear plasticizers e.g. BIO and DOA have higher compabilities with PVC, a branched plasticizer e.g. TOTM showed higher mechanical properties. Moreover, a new spectrophotometric method for determination of plasticizer migration from PVC polymer matrix to the surface of artifical leather was developed. According to lightness change on the surface of PVC artifical leather before and after heat treatment at 70 °C, the migration rates of used plasticizers increase in this order: TOTM < TBTM < DOTP < BIO < DOA. © 2020 Elsevier B.V.Article Citation - WoS: 19Citation - Scopus: 22Enhanced Methylene Blue Removal Efficiency of Tio2 Embedded Porous Glass(Elsevier Ltd., 2021) Ertuş, E.Burak; Vakıfahmetoğlu, Çekdar; Öztürk, AbdullahA porous glass (PG) embedded with titanium dioxide (TiO2) was produced via impregnation of the PG with Titanium (IV) Isopropoxide solution followed by crystallization. N2 sorption analyses revealed that the specific surface area (SSA) and total pore volume of the PG reached to 358 m2/g and 0.370 cm3/g, respectively. The adsorption capacity of methylene blue (MB) for the glasses was measured in the dark, instead the photocatalytic MB removal efficiency was evaluated by the degradation of MB under UV light illumination using a UV–vis spectrometer. The MB removal efficiency of the TiO2 synthesized anatase powder was only 32.3 % whereas, for TiO2 embedded PG (TiPG) it was 91.6 %, and nearly complete (> 99 %) efficacy was achieved for TiO2 embedded alkaline leached PG (TiPG-AL) under UV illumination 3 h period. Better MB removal efficiency was attributed to high SSA and dispersion of nano size anatase TiO2 crystallites within the porous structure. © 2020 Elsevier LtdArticle Citation - WoS: 63Citation - Scopus: 65Amidoxime Functionalized Polymers of Intrinsic Microporosity (pim-1) Electrospun Ultrafine Fibers for Rapid Removal of Uranyl Ions From Water(Elsevier Ltd., 2019) Satılmış, Bekir; Isık, Tuğba; Demir, Mustafa Muammer; Uyar, TamerThe Polymers of Intrinsic Microporosity (PIM-1) is considered as one of the most promising polymer candidates for adsorption applications owing to its high surface area and the ability to tailor the functionality for the targeted species. This study reports a facile method for the preparation of amidoxime functionalized PIM-1 fibrous membrane (AF-PIM-FM) by electrospinning technique and its practical use for the extraction of U(VI) ions from aqueous systems via column sorption under continuous flow. Fibrous membrane form of amidoxime functionalized PIM-1 (AF-PIM-FM) was prepared by electrospinning method owing to its excellent processability in dimethylformamide. Bead-free and uniform fibers were obtained as confirmed by SEM imaging and average fiber diameter was 1.69 +/- 0.34 mu m for AF-PIM-FM. In addition, electrospun PIM-1 fibrous membrane (PIM-FM) was prepared as a control group. Structural and thermal characterization of powder and membrane forms of the materials were performed using FT-IR, H-1 NMR, XPS, Elemental analyses, TGA, and DSC. The porosity of the samples was measured by N-2 sorption isotherms confirming amidoxime PIM-1 still maintain their porosity after functionalization. Amidoxime functionality along with membrane structure makes AF-PIM-FM a promising material for uranyl adsorption. First, a comparison between powder and membrane form of amidoxime functionalized PIM-1 was investigated using batch adsorption process. Although membrane form has shown slightly lower adsorption performance in the batch adsorption process, the advantage of using the membrane in column adsorption processes makes membrane form more feasible for real applications. In addition, amidoxime modification enhanced the uranium adsorption ability of PIM-FM up to 20 times. The effect of initial concentration and pH were investigated along with regeneration of the adsorbents. AF-PIM-FM was successfully used for five adsorption-desorption cycles without having any damage on the fibrous structure.Article Citation - WoS: 7Citation - Scopus: 7Increasing Spontaneous Wet Adhesion of Dopa With Gelation Characterized by Epr Spectroscopy(Elsevier Ltd., 2019) Göksel, Yaman; Akdoğan, YaşarThe presence of water molecules around both adhesive materials and surface results in the hydration barriers that weaken adhesion. In nature, mussels attach to various types of surfaces by using 3,4-dihydroxyphenylalanine (DOPA) containing mussel foot proteins. DOPA shows wet adhesive properties before and after contribution in the hydrogel formation. Here, the wet adhesive properties of DOPA modified four armed poly (ethylene glycol) polymer (PEG-(DOPA)(4)) and its hydrogels induced by (IO4)(-) or (Cr2O7)(2-) ions are compared by using electron paramagnetic resonance (EPR) spectroscopy in terms of their surface coverages. In water, spin labeled hydrophobic polystyrene (SL-PS) and hydrophilic silica (SL-SiO2) nanoparticles are prepared, and the percentages of their covered surface values are obtained. Without applying force, the adhesion to SL-PS increases in the order of PEG-(DOPA)(4) < PEG-(DOPA)(4) + (IO4)(-) hydrogel < PEG-(DOPA)(4) + (Cr2O7)(2-) hydrogel with the percentages of surface coverages 65%, 76% and 93%, respectively. Although, neither of PEG-(DOPA)(4) polymer and (IO4)(-) induced PEG-(DOPA)(4) hydrogel adhere to SL-SiO2 nanoparticle spontaneously, (Cr2O7)(2-) induced PEG-(DOPA)(4) hydrogel adhere to SL-SiO2 with a 59% of surface coverage. These results show that gelation mechanisms of DOPA have effect on the spontaneous adhesion of DOPA to the wet surfaces even for the hydrophilic silica surface.Article Citation - WoS: 33Citation - Scopus: 40Preparation of Albumin Nanoparticles in Water-In Liquid Microemulsions(Elsevier Ltd., 2019) Demirkurt, Begüm; Çakan Akdoğan, Gülçin; Akdoğan, YaşarIonic liquids (Its) with a variety of properties have been considered a unique class of solvents. Using ILs in microemulsions as oil substitutes provides environmentally benign media for various applications including nanoparticle synthesis. Here, bovine serum albumin nanoparticles (BSA NPs) widely used in drug delivery studies were prepared in nano-sized water droplets of water-in-IL (W/IL) microemulsion systems. A hydrophobic IL of 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF(6)) was used as oil component in place of oils (castor oil, olive oil, etc.) and/or conventional organic solvents (cyclohexane, dichloromethane, etc.) in an emulsification method. In order to obtain spherical BSA NPs, high speed homogenizer treatment was applied followed by glutaraldehyde addition. Effects of glutaraldehyde, speed of homogenizer, type of surfactants and compositional fractions of the microemulsion components on the formation of water droplets and/or preparation of BSA NPs were studied using FTIR, EPR, DLS, and SEM techniques. Optimization of these preparation parameters showed that 3 wt% of BSA in a water/Tween 20/BmimPF(6) microemulsion with 20:50:30 wt% yielded similar to 100 nm average sized BSA NPs based on the SEM analysis. Although, water droplet size strongly depends on the water content, BSA nanoparticle size did not show a significant dependency on the water content. On the other hand, surfactant/IL weight ratio is more crucial for obtaining more uniformly size distributed albumin nanoparticles. A significant cellular uptake of BSA NPs prepared in IL based microemulsions with high cell viability showed the potential of this technique in preparation of albumin nanoparticles that can be used also in drug delivery studies. (C) 2019 Elsevier B.V. All rights reserved.