LEE- Tekstil Mühendisliği Lisansüstü Programı
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Yazar "Başkan, Havva" ile LEE- Tekstil Mühendisliği Lisansüstü Programı'a göz atma
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ÖgeElectrospun composite nanofibers with metal/metal oxidenanoparticles(Graduate School, 2021-04-21) Başkan, Havva ; Karakaş, Hale ; 503142809 ; Textile Engineering ; Tekstil MühendisliğiFunctional materials have taken great interest due to their superior physical and chemical features which allow them to be succesfully used in a wide range of engineering applications. Nanomaterials, specifically nanofibers are regarded as functional materials due the their high surface area to volume ratio, high pore interconnectivity, small pore dimensions and superior chemical and mechanical features. Nanofibers are produced by mainly electrospinning which is a simple and inexpensive technique. Moreover, many types of polymers or polymer blends can be converted to nanofibers by electrospinning. Combination of two or more materials in a nanofibrous structure can result in functional materials. In this thesis, the goal was obtaining functional nanofibrous materials by incorporating a noble metal (silver) and metal oxides (iron III oxide (Fe3O4) and aluminum oxide (Al2O3)) in novel polymeric nanofiber structures and evaluate the biological features of the samples for medical applications. First of all, a novel Poly (acrylonitrile-co-itaconic acid) (P (AN-co-IA)) copolymer was synthesized by emulsion polymerization. In the literature, copolymerization of itaconic acid (IA) with acrylonitrile (AN) was performed for decreasing the cyclization temperature of polyacrylonitrile (PAN) homopolymer and consuming less energy for carbon fiber production. However, in the scope of the thesis, it was aimed to enhance the application areas of IA by integration of metals and metal oxides. Since Fe3O4 nanoparticles and Al2O3 nanoparticles play an imperative role in many biomedical applications, they were utilized together with P (AN-co-IA) copolymer. It was very difficult to study with metal oxide nanoparticles due to their tendency to agglomeration. For that reason, the appropriate amount of metal oxide nanoparticles was determined first by using polyacrylonitrile /N,N Dimethylformamide (PAN/DMF) solutions. Afterwards, the optimized amout of Fe3O4/ Al2O3 nanoparticles were added into P (AN-co-IA)/DMF polymer solutions and the solutions were subjected to electrospinning to obtain a nanofibrous structure. In addition to conventional electrospinning, coaxial electrospinning was also performed for metal oxide nanoparticle incorporation. Detailed morphologic and spectroscopic characterizations of the obtained nanofibers were performed. Thermal features of the resultant nanofibers were also analyzed by Differential Scanning Calorimety (DSC) and Thermogravimetric Analysis (TGA). It was captured from the characterization results that addition of metal oxide nanoparticles to P (AN-co-IA) copolymer structure altered the features of the plain P (AN-co-IA) nanofibers. Even using very small amount (1 wt %) of Al2O3 caused improvements in thermal stability of the nanofibers. On the other side, silver nanoparticles (AgNPs) formation and integration to polymer structures were achieved by different chemical and physical methods. By the assistance of P (AN-co-IA) polymer and DMF, AgNPs were formed in-situ in polymer solution and then the polymer solution was electrospun for nanofiber production. The novelty of the method was related to the decreased reduction duration of silver nitrate (AgNO3) by using P (AN-co-IA) polymer. The method was compared with the literature studies on the utilization of PAN polymer for reduction of AgNO3. P (ANco-IA) polymer allowed to obtain AgNPs from the precursor AgNO3 two times faster than PAN. Moreover, it was understood that P(AN-co-IA)/Ag nanofibers had high electrical conductivity, enhanced thermal stability and satisfying nanofiber morphologies. Besides conventional electrospinning, AgNPs were introduced into P(AN-co-IA) polymer structure via coaxial electrospinning. In the process, AgNO3/DMF solution was prepared to be used as a shell solution and P (AN-co- IA)/DMF solution was prepared as a core solution. Since the most important point in coaxial electrospinning is the feed-rate of core and shell solutions, a set of experimental study was performed for the optimization of flow-rate (0.2 ml/h) of shell solution. After coaxial electrospinning, P(AN-co-IA)(core)/ AgNO3 (shell) nanofibers were subjected to UV-irradiation to generate AgNPs by the reduction of AgNO3. UVirradiation duration was optimized as 3 hours by using PAN(core)/ AgNO3 (shell) nanofibers. In addition to P (AN-co-IA) and PAN polymers, biodegradable and biocompatible poly (3-hydroxybutyrate) P (3HB) and poly (3-hydroxyoctanoate-3 hydroxydecanoate)(P (3HO-3HD)) polymers were also utilized for the combination of AgNPs. To this end, nanofibers of P (3HB)/P (3HO-3HD) were collected via conventional electrospinning and by dip-coating they were coated with AgNPs. As in the nanofibers including metal oxide nanoparticles, detailed morphologic, spectroscopic and thermal characterizations of the resultant nanofibers were performed by Scanning Electron Microscope –Energy Dispersive Spectroscopy (SEM-EDS), Ultra Violet-Visible (UV-Visible) and Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy, and DSC. Most importantly, antimicrobial activity studies of P(AN-co-IA)/Ag nanofibers (obtained via conventional electrospinning) against S. aureus, E.coli, P. aeruginosa and C. albicans and immunomodulatory properties of P (3HB)/P (3HO-HD)/Ag nanofibers against special cytokines (IL-1 (α and β), IL-6, IL-8, TNF-α, TGF-β and HBD-2) were evaluated. Related to the antimicrobial activity results of P (AN-co-IA)/Ag nanofibers, it was observed that the nanofibers produced inhibition zones against the studied microorganisms. That was also proved by susceptibility testing. According to time-kill analysis, without silver nanoparticles, either PAN or P (AN-co-IA) nanofibers did not show any antimicrobial activity against any microorganisms. However, bacteriostatic/fungistatic activity was observed for all nanofiber samples which include AgNPs at almost all time points. Bactericidal activity was started from 24-48 hours and lasted until 120 hours at 10x Minimum Inhibitory Concentration (MIC) whereas fungicidal activity was observed between 120 and 168 hours at 10xMIC. Based on the real-time reverse transcriptase polymer chain reaction (RT-PCR) tests of P (3HB)/P (3HO-3HD)/Ag nanofibers, it was understood that while plain P(3HB)/P(3HO-3HD) nanofibers did not show any difference in the basal production of these molecules by HaCaT cells in culture, AgNP-containing P(3HB)/P(3HO-3HD) nanofibers upregulated the studied proinflammatory cytokines which were IL-1(α and β), IL-6 and IL-8 after 6 hours to start the healing process. Those findings of AgNPs containing P (AN-co-IA) and P (3HB)/P (3HO-3HD) nanofibers revealed that they could be used in wound dressing or tissue engineering applications effectively. Polypyrrole (PPy) is popular with its conductivity, but it can also be used in biological applications such as biosensors and drug delivery. However, due to the problems in processing with PPy, it is very difficult to obtain PPy nanofibers. In this thesis, it wasaimed to combine PPy with AgNPs to be used in biological applications and also converting it to a nanofibrous web structure by the help of P (AN-co-IA). Since it was difficult to electrospin P (AN-co-IA), PPy and AgNPs in a single step, AgPPy was synthesized via chemical oxidation polymerization first. Then AgPPy and P (AN-co-IA) was gathered in a nanofiber structure via coaxial electrospinning. AgPPy/DMF solution was prepared as shell solution and P (AN-co-IA) /DMF was prepared as core solution. It can be fairly said that the same protocol of the abovementioned coaxial electrospinning was performed for coaxial electrospinning of P (AN-co-IA) (core)/AgPPy (shell) nanofibers. Bead-free and continuous nanofiber morphologies with fine nanofiber diameters could be obtained. As a conclusion, in the scope of this thesis, functional nanofibers were achieved by incorporating metal/metal oxide nanoparticles into polymeric nanofiber structures with various experimental procedures. The obtained nanofibers are good candidates for medical applications where conductivity and antimicrobial activity are desired.