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    Antibiotic loaded electrospun poly (lactic acid) nanofiber mats for drug delivery system
    (Elsevier, 2022) Suner, Salih Can; Yildirim, Yeliz; Yurt, Fatma; Ozel, Derya; Oral, Ayhan; Ozturk, Ismail
    Active material-loaded nanofibers becoming more important, because of their applications in many areas such as wound healing, skin engineering, and drug release. This study was conducted to compare the release kinetics of three different antibiotics loaded on nanofibers in Phosphate-buffered saline (PBS) solution and their inhibition properties against bacteria. The three different commercial antibiotics; vancomycin (VAN), ceftriaxone (CFT), and cefpodoxime (CFD) were loaded into Polylactic acid (PLA) nanofibers via electrospinning process with different percentages; 5%, 7.5%, and 10% weight ratios of PLA. The SEM images of PLA/Antibiotic nanofibers and pure PLA nanofiber revealed an increase in diameters with the presence of antibiotics embedded in PLA nanofiber. The TGA analysis showed that the thermal degradation of CFD and VAN-loaded nanofibers were higher than neat PLA, while the thermal stability of CFT loaded nanofibers was the lowest. In the Tan Delta curves, the Tg temperatures of CFD, VAN, CFT loaded nanofibers and pure PLA nanofiber were determined as 54.56 degrees C, 54.57 degrees C, 53.86 degrees C, and 53.55 degrees C, respectively. As can be seen from the results, the variation of the glass transition temperatures supports the DSC data. Drug releasing behaviors of PLA/Antibiotic nanofibers were investigated by Ultraviolet-Visible Spectroscopy at 280, 242 and 230 nm wavelength for VAN, CFT, and CFD antibiotics, respectively. Drug-releasing amounts were gradually increased by increasing the drug loading amounts from 5% to 10%. PLA-VAN, PLA-CFT, and PLA-CFD nanofibers which contain 10% of drugs were delivered about 79%, 75%, and 29% of drugs linearly within nearly 380 h, 500 h, and 360 h, respectively. The formulations including CFT at different concentrations were found to be effective against Staphylococcus aureus and Escherichia coli in a dose-dependent manner. The formulations including CFD and VAN at different concentrations have also inhibited the growth of S. aureus.
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    Structural changes in Poly(lactic acid)-zeolite nanocomposites exposed to 60Co gamma rays
    (Taylor & Francis Ltd, 2018) Yildirim, Yeliz; Oral, Ayhan
    Poly(lactic acid) (PLA) nanocomposites containing 3%, 5% and 7% zeolite used in the present research study were prepared by solution casting. The PLA nanocomposites were structurally characterized by Scanning Electron Microscopy and Fourier-transform infrared spectroscopy. The effects of the gamma radiation at the absorbed doses of 10, 15 and 20kGy on the structures and thermal properties of the nanocomposites were investigated in a tetrahydrofuran solvent. Thermodecomposition tests and analyses were carried within 30-500 degrees C range at the rate of 10 degrees Cmin(-1) by thermogravimetric analysis (TG). The activation energies for thermal degradation of the nanocomposites were calculated from their TG data by Flynn-Wall-Ozawa method. The G values of the nanocomposites were calculated based on molecular weights which were measured by means of gel permeation chromatography before and after the gamma irradiation. The E-a and molecular weight results showed that addition of zeolite to the PLA affected the radiation resistance of the polymer.
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    Öğe
    The influence of ?-ray irradiation on the thermal stability and molecular weight of Poly(L-Lactic acid) and its nanocomposites
    (Pergamon-Elsevier Science Ltd, 2014) Yildirim, Yeliz; Oral, Ayhan
    The gamma (gamma) radiation effects on the thermal properties of Poly(L-Lactic acid) (PLLA), and three PLLA nanocomposites containing 1, 3 and 5% montmorillonite MK10 clay were investigated in different solvents such as tetrahydrofuran, chloroform and 1,4 dioxane. The polymers were irradiated by gamma radiation at low absorbed doses of 1, 5, and 10 kGy. The thermal properties and molecular weight of the unirradiated and irradiated PLLA and its nanocomposites were characterized by Thermogravimetry (TG) and Gel Permeation Chromatography (GPC), respectively. The TG curves showed that the thermal degradation of the unirradiated PLLA and its nanocomposites occurred in only one stage. The activation energies of thermal degradation (E) for irradiated and unirradiated PLLA and its nanocomposites were determined by the Flynn-Wall-Ozawa (FWO) method. The E values of the polymer irradiated with gamma radiation seem to be smaller than those of unirradiated sample due to polymer bond scission. In addition, the calculated G values of the polymer and nanocomposites showed that the polymer structure was less stable when exposed to radiation with increasing % MK10 content. (C) 2013 Elsevier Ltd. All rights reserved.