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    Investigation of mechanical and printing properties of poly(lactic acid) and its composite filaments used in 3D printing
    (Springer, 2024) Sahin, Goekcen; Ozyildirim, Hasan; Sahin, Anil
    In this work, we investigated how the mechanical and printing properties of poly(lactic acid) (PLA) and its composite filaments, which are increasingly used in 3D printers, changed in a humid environment. PLA filament, PLA/Graphite, and PLA/polyhydroxybutyrate (PHB) composite filaments were used in these experiments. The filaments were exposed to 80% relative humidity for 15 days, and standard dog-bone specimens were printed by these filaments. Tensile tests were applied to the filaments and printed specimens, Fourier transform infrared spectrometry (FTIR) was performed, and scanning electron microscopy (SEM) micrographs of the specimens and their fractured surfaces were obtained. The tensile strength of the PLA filament, PLA/Graphite, and PLA/PHB composite filaments exposed to a humid environment decreased compared with the reference specimens. When the experiments were evaluated, it was observed that the print quality and tensile strength decreased in dog-bone specimens printed from PLA filament and PLA/Graphite composite filament exposed to a humid environment. The tensile strength decreased in the PLA specimen by 29.5% and the PLA/Graphite composite specimen by 28% compared with the reference specimens. In contrast, for dog-bone specimens printed from PLA/PHB composite filaments, print quality and tensile strength increased. The tensile strength increased by 8.5% in PLA/PHB composite specimens. The band changes in the FTIR spectra of the dog bone and conditioned specimens produced from PLA filament, PLA/Graphite, and PLA/PHB composite filaments showed the chemical changes in the specimens.
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    Synthesis of novel dimeric compounds containing triazole using click method and their selective antiproliferative and proapoptotic potential via mitochondrial apoptosis signaling
    (Springer Birkhauser, 2020) Karabulut, H. R. Ferhat; Karatavuk, Ali Osman; Ozyildirim, Hasan; Doganlar, Oguzhan; Doganlar, Zeynep Banu
    In this study, the main aim was synthesis of dimeric compounds, which contain lithocholic acid and a triazole structure to investigate the selective cellular and molecular antiproliferative and proapoptotic potential of these products in healthy embryonic fibroblast (MEF), cervix cancer (HeLa), and breast cancer (MCF-7) cells. Four ester (5a-d) and five dimeric (6a-d, 7) out of nine novel compounds were obtained. First of all, lithocholic acid was converted to methyl lithocholate and then it was reacted with certain alkynoic acids (a-d) to obtain its alkynoate derivatives (5a-d). Finally, these compounds were converted to dimers (6a-d) by using 2,6-bis(azidomethyl)pyridine via the click method. Our result indicate that, treatment with dimeric compounds can selectively decrease the cell viability and proliferation in cervix cancer HeLa and breast cancer MCF-7 cells, except 7 which caused a strong cytotoxicity on healthy MEF cells. According to MTT assay, Nucblue cell stain and Annexin V/Propodium iodide molecular probe staining, 100 mu M concentrations of the dimeric compounds was sufficient in inducing death and apoptotic cell ratio in HeLa and MCF-7 breast cancer cells selectively. In brief, the present study indicates that most effective dimeric compounds are 6a and 6b, which have the highest IC50 (345.8-342.6 mu M) value on healthy cell and the lowest IC50 value in both cervix (49.2-36.9 mu M) and breast (23.0-66.1 mu M) cancer cells especially long-term treatment and which triggers apoptosis pathway specifically.