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    3D-Printed Biocomposites from Hemp Fibers Reinforced Polylactic Acid: Thermal, Morphology, and Mechanical Performance
    (North Carolina State Univ Dept Wood & Paper Sci, 2025) Celik, Esra; Uysal, Mesut; Gumus, Omer Yunus; Tasdemir, Cagatay
    Thermal, morphological, and mechanical properties were studied for 3D- printed biocomposites prepared from polylactic acid (PLA) and hemp fibers. For this purpose, the neat PLA, PLA/Hemp fiber (3 wt%), PLA/Hemp fiber/Maleic anhydride (3 wt% and 0.6 wt%), and PLA/Hemp fiber/Maleic anhydride/Glycerol (3 wt% and 0.6 wt% + Glycerol added in 10% of PLA) biocomposites were extruded to obtain filaments for fused filament fabrication (FFF). Thermogravimetric analysis (TGA) provided temperatures corresponding to 5%, 10%, and 90% mass losses for materials before and after 3D printing. During 3D printing, filaments were extruded with a nozzle temperature of 220 degrees C; consequently, their thermal properties worsened after 3D printing. In thermal analysis, T g increased by adding hemp fiber and maleic anhydride but was decreased with glycerol addition. The tensile and flexural strengths of neat PLA and biocomposites were not statically different, but flexural strength was slightly increased by adding ingredients one by one. Regarding modulus of elasticity (MOE) of materials, the sample group of the PLA/hemp fiber/maleic anhydride had the highest value. However, glycerol addition decreased MOE by 17%. These results showed that material performance of the PLA could be improved or remain statistically identical by adding hemp fiber, maleic anhydride, and glycerol.
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    DNA and hemoglobin binding activities: Investigation of coumarin-thiosemicarbazone hybrids
    (Academic Press Inc Elsevier Science, 2024) Celik, Esra; Meletli, Furkan; Ozdemir, Mucahit; Koksoy, Baybars; Danis, Ozkan; Yalcin, Bahattin
    Coumarin and coumarin-thiosemicarbazone hybrids were synthesized and characterized by various techniques such as FT-IR, 1H NMR, 13C NMR, MALDI-TOF-MS spectroscopy, and single crystal X-Ray diffractometer (XRD). The photochemical and photophysical properties of the compounds, such as solvatochromism, solubility, and chemical reactivity, were analyzed using UV-vis spectroscopy in different solvents. Due to the potential biological activities of the synthesized compounds, their binding affinity and mechanisms with calf thymus DNA (ctDNA) and bovine hemoglobin (BHb) were determined using several useful spectrophotometric and theoretical approaches such as UV-vis absorption and fluorescence spectroscopy, molecular docking, and density functional theory (DFT). The experimental results showed that the compounds exhibited strong binding interactions with DNA and BHb. Additionally, the compounds demonstrated predominantly binding modes, such as intercalation and groove binding with DNA and pi-pi stacking interactions with BHb. To better understand the thermodynamics of these interactions, quenching constants, binding constants, and Gibbs free energy changes (Delta G degrees) were calculated. Molecular docking and DFT results supported the experimental data regarding the binding affinity and mechanisms of the compounds to DNA and BHb. Overall, this comprehensive study on coumarin and coumarin-thiosemicarbazone hybrids provides valuable insights into their interaction mechanisms with critical biomolecules, highlighting their potential in therapeutic applications as multifunctional agents.