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    Electrospun PCL/PVP nanofibers embedded with magnetic nanoparticles: Correlating porosity, structure and magneto-thermo-mechanical properties
    (Elsevier, 2026) Pekdemir, Sibel Selcuk; Pekdemir, Mustafa Ersin; Ulu, Ahmet; Kuzu, Serpil Yalcin
    Smooth and homogeneous PCL/PVP-Fe3O4 composite nanofibers with varying magnetic nanoparticle (MNP) contents were successfully fabricated via a simple electrospinning technique. The influence of Fe3O4 MNP incorporation on the structural, morphological, thermal, magnetic, and physicochemical properties of PCL/PVP nanofibers was systematically investigated using ATR-IR, TGA, DTA, SEM, EDX, XRD, and VSM analyses. ATR-IR and XRD results revealed strong interactions between Fe3O4 and the polymer matrix, indicating significant structural modification and enhanced crystallinity. The optimized nanofibers exhibited uniform diameters (400-600 nm) and smooth, interconnected surfaces, confirming the efficiency of the electrospinning parameters. EDX mapping verified the homogeneous distribution of Fe3O4 MNPs across the nanofibers. The incorporation of Fe3O4 notably improved the thermal stability and magnetic response, achieving a saturation magnetization of 5.30 emu/g at 10 wt% Fe3O4 content. Moreover, the presence of rigid inorganic particles enhanced mechanical stability while slightly reducing swelling behavior due to restricted polymer chain mobility. Overall, the synergistic effects of PCL/PVP blending and Fe3O4 loading produced nanofibers with balanced thermal, magnetic, and mechanical performance. The results suggest that optimizing the thermal, magnetic, and mechanical properties of PCL/PVP- Fe3O4 composite nanofibers can endow them with versatile functional material potential.
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    Nature-derived otolith loaded polyethylene glycol-polycaprolactone electrospun composite nanofiber membranes: preparation, characterization, and biocompatibility evaluation
    (Springer, 2025) Pekdemir, Sibel Selcuk; Gedik, Kubra Karadas; Kurucay, Ali; Onay, Hatice; Ulu, Ahmet; Pekdemir, Mustafa Ersin; Kolak, Seda
    The electrospun nanofibers have paid much attention to biomedical applications. In this study, the electrospun composite nanofibers were prepared based on optimized polycaprolactone (PCL, 12 wt%) and polyethylene glycol (PEG, 3.6 wt%) polymers loaded with otoliths particles (OTO, 10-30 wt%) by electrospinning technique. The morphological, molecular interactions, crystallinity, and thermal properties of the composite nanofiber membranes were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. In addition to that, swelling behaviors, biodegradability, porosity, and biocompatibility were also evaluated. Both PEG/PCL and OTO/PEG/PCL nanofibers revealed bead-less constructions with average diameters of around 500 nm. Thermogravimetric analysis revealed OTO/PEG/PCL composite membranes thermally stable up to 300 degrees C. XRD results also indicated a good crystallinity for the OTO/PEG/PCL composite membranes due to higher crystallinity of otolith. Adding otolith to PEG/PCL nanofibers did not obviously change the water uptake capacity, biodegradability, and porosity while increasing swelling ratio. Finally, membranes with the lowest otolith concentration (10% w/w) showed 96.2% cell viability, while increasing otolith concentration decreased cell viability. Based on the obtained results, the cytotoxicity of OTO/PEG/PCL membranes was evaluated with mouse fibroblast (L-929) cells by more than 85% survival during 72 h, which revealed that the OTO/PEG/PCL membranes were non-toxic. Taken together, these data suggest that OTO/PEG/PCL membranes could potentially be used as a nanofiber scaffold for applications.
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    PCL/chitosan composite films enhanced with Bi2O3 in nuclear shielding applications: Irradiation resistance, thermal and structural properties
    (Wiley, 2025) Yilmaz, Demet; Pekdemir, Mustafa Ersin; Dik, Gamze; Pekdemir, Sibel Selcuk; Ulu, Ahmet; Tasgin, Yahya; Ates, Burhan
    In this work, irradiation resistance, thermal, and structural characteristics of Bi2O3-reinforced poly epsilon-caprolactone/chitosan composites for nuclear shielding applications were studied. PCL/CTS/Bi2O3 composite films were prepared by using different amounts of Bi2O3 (0.5%-4.0% (w/v)). The radiation shielding parameters of the synthesized composite films were both experimentally and theoretically measured at the high energy region. The equivalent dose rates of the prepared film samples were measured using a fast neutron source. Also, to determine the irradiation resistance, the samples were irradiated with Am-241 and Co-60 sources for 30 days. The MFP values at 80.99 keV changed by approximately 61% in samples PCL/CTS and PCL/CTS/4% Bi2O3. The results show that Bi2O3 content increases the gamma shielding abilities in PCL/CTS films. According to TGA results, the thermal stability of the polymer composite films is increased by the addition of Bi2O3 to the PCL/CTS blend film. The results show that PCL/CTS composite materials can be used as protective coating materials for nuclear shielding.Highlights PCL/CTS/Bi2O3 composite films were prepared by the solvent casting method. The thermal stability of the composite films increased by increasing the Bi2O3 amount. Bi2O3 increased the LAC and MAC values of the composite films. PCL/CTS/Bi2O3 composite films have a neutron shielding effect.
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    Unveiling the effect of molecular weight of vanillic acid grafted chitosan hydrogel films on physical, antioxidant, and antimicrobial properties for application in food packaging
    (Elsevier, 2024) Bakar, Buesra; Pekdemir, Sibel Selcuk; Birhanli, Emre; Ulu, Ahmet; Pekdemir, Mustafa Ersin; Ates, Burhan
    Till now, a wide range of chitosan (CHS)-based food packaging films have been developed. Yet, the role of molecular weight (MW), which is an important physical property of CHS, in determining the physicochemical and biochemical properties of vanillic acid (VA)-grafted CHS hydrogel films synthesized using CHS with different MWs has not been investigated until now. Three kinds of CHS including low, medium, and high MWs were grafted separately with VA through a carbodiimide mediated coupling reaction. No significant difference in water resistance properties was observed with increasing MW of CHS, in contrast to obvious decrease in light transmittance and opacity. The VA-g-CHS hydrogel films exhibited significantly improved light blocking capacity. A significant improvement in antioxidant (similar to 6-fold) and antimicrobial (similar to 1.2-fold) activity was observed after grafting with VA. In contrast, the free radical scavenging and antimicrobial activity decreased with increasing MW of CHS. Most importantly, VA-g-CHS hydrogel films could maintain the freshness of cherry tomatoes for up to 10 days at similar to 25 degrees C. However, no significant difference was observed depending on the MW value of CHS. This pioneering work is of great importance in guiding the selection of MW of CHS biomacromolecule to design hydrogel films with desired physicochemical and biochemical properties.
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    Valorization of bio-calcium carbonate based Chamelea gallina shell waste fillers in shape memory polymer composites
    (Wiley, 2024) Pekdemir, Sibel Selcuk; Onay, Hatice; Oner, Ecem Ozen; Pekdemir, Mustafa Ersin; Kok, Mediha; Ates, Burhan; Aydogdu, Yildirim
    In recent years, the focus has been on the use of calcium carbonate-based seashell wastes in the production of new thermoplastic and thermoset polymer materials, paving the way for their use as biofillers in polymeric composites. In this study, it is aimed to obtain a new polymeric composite material by doping Chamelea gallina shells, on polylactic acid (PLA)/polyethylene glycol (PEG) blend. Structural characterization of the obtained PLA/PEG blend/C. gallina composite films was performed with attenuated total reflection infrared spectroscopy (ATR-IR). When the thermal properties of composite materials were examined by thermogravimetric analysis (TGA), it was determined that the thermal stability of polymeric composites increased with the addition of C. gallina. SEM images showed that the polymer blend films, which appeared to have a porous structure, filled the pores with increasing C. gallina ratio. It was observed that the biodegradability of PLA/PEG blend composite films decreased with increasing C. gallina shells addition. However, C. gallina had a positive effect on the swelling and water absorption capacities of polymeric composites. The increase in tensile strength and elongation at break values of PLA/PEG blend/C. gallina composite films with increasing C. gallina means that the mechanical properties of the polymer are improved.