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    Characterization of short-length multi-walled carbon nanotubes and cytotoxicity on MDA-MB-231 and HUVEC cell lines
    (Springer Japan Kk, 2020) Dinc, Bircan; Unlu, Ayhan; Bektas, Muhammet
    Multi-walled carbon nanotubes (MWNTs) are suitable for delivering large biomolecules with lower cytotoxicity values and low prime cost. Surface modifications of MWNTs affect interaction with cells and proteins. Oxidation with strong acids decreases cytotoxicity of CNTs and increases protein-loading capacity. Here, after oxidation, TEM images revealed more aligned structure and carboxylated groups at the surface which decreases toxicity. Functionalized MWNTs showed more gradual degradation than the pristine MWNTs and mass loss increased by 2% in the same temperature range. Raman spectroscopy corrected graphitic structure with characteristic D and G bands at 1330 and 1579 cm(-1) and increased intensity after oxidation. FTIR spectroscopy peaks at 1443 cm(-1), 1560, 1640 cm(-1), 2100-2200 cm(-1) and 3426 cm(-1) are ascribed to C-O-C vibrational stretch, C=C bonds, vibration of C equivalent to C bonds and stretch of hydroxyl groups, respectively. The sonication-driven dispersion of in phosphate-buffered saline, distilled water and cell culture medium were detected by UV-vis-NIR spectroscopy, water-dispersed functionalized MWNTs revealed the highest absorbance value. Cytotoxicity of MWNTs was investigated before and after functionalization in breast cancer (MDA-MB-231) and human vein endothelial (HUVEC) cells. Relatively low-toxicity results were obtained in functionalized MWNTs and cellular uptake of MWNTs were corrected with fluorescent imaging of cells and cell lysates. Protein-loading capacity of fsMWNTs (functionalized short-length multi-walled carbon nanotubes) was evaluated by using bovine serum albumin (BSA) and with an equal amount of fsMWNTs and BSA; 36% binding yield was obtained. Protein corona after covalent functionalization potentially lowered cytotoxicity up to 6%.
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    A Comparative Study of Short Multi-Walled Carbon Nanotubes with Different Bulk Densities
    (Maik Nauka/Interperiodica/Springer, 2022) Dinc, Bircan; Ustunsoy, Recep; Unlu, Ayhan; Meran, Mehdi; Karatepe, Nilgun; Bektas, Muhammet
    Multi-walled carbon nanotubes (MWNTs) were investigated before and after carboxylic acid functionalization. Here, the comparative analysis of MWNTs with different bulk densities reveals similar Raman and FTIR spectra before and after acid functionalization except for minor differences. However thermal analyses exhibited some basic differences for both MWNTs before and after acid treatment. We investigated the cytotoxicity of two MWNTs on HT-29 and HEK293-T cells through three different methods: MTT assay, DAPI staining, and xCELLigence real-time cell analyzing method. It was observed that high bulk density affects the cytotoxicity for both cell lines and in all methods. Because the acid treatment lowered the bulk density, after acid treatment, the MWNTs with the higher bulk density (C150P) elicited similar cytotoxicity compared to the lower one (C70P).
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    Cytotoxicity of doxrubicin loaded single-walled carbon nanotubes
    (Springer, 2018) Unlu, Ayhan; Meran, Mehdi; Dinc, Bircan; Karatepe, Nilgun; Bektas, Muhammet; Guner, F. Seniha
    Carbon nanotube (CNTs) is a new alternative for efficient drug delivery and it has a great potential to change drug delivery system profile in pharmaceutical industry. One of the important advantage of CNTs is their needle-like, cylindrical shape. This shape provides a high surface area for multiple connections and adsorption onto for millions of therapeutic molecules. CNTs can be internalized by cells via endocytosis, passive diffusion and phagocytosis and release the drug with different effects like pH and temperature. The acidic nature of cancer cells and the susceptibility of CNTs to release the drug in the acidic environment have made it a promising area of research in cancer drug delivery. In this research, we investigated cell viability, cytotoxicity and drug delivery in breast cancer cell line by designing non-covalent single walled carbon nanotubes (SWNT)-doxorubicin (DOX) supramolecular complex that can be developed for cancer therapy. Applied high concentrations of DOX loaded SWNTs changed the actin structure of the cells and prevented the proliferation of the cells. It was showed that doxorubicin loaded SWNTs were more effective than free doxorubicin at relatively small concentrations. Once we applied same procedure for short and long (short: 1-1.3 mu m; long: 2.5-4 mu m) SWNTs and compared the results, more disrupted cell structure and reduction in cell proliferation were observed for long CNTs. DOX is bounded more to nanotubes in basic medium, less bound in acidic environment. Cancer cells were also examined for concentration at which they were effective by applying DOX and it was seen that 3.68 mu M doxorubicin kills more than 55% of the cells.
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    Investigation of the three-dimensional structure and interaction mechanism of poly (ADP-ribose) polymerase 4
    (Taylor & Francis Ltd, 2020) Unlu, Ayhan; Dinc, Bircan
    Poly ADP-ribose polymerases (PARPs) are family of proteins that use nicotinamide adenine dinucleotide (NAD) as substrate. Seventeen putative PARP sequences were determined in the human genome. Although PARPs show a variety of functions and low sequence identities, they share common structural and functional properties. In our study, PARP1 and PARP2 and PARP4 sequences in different species were compared; it was found that active sites of PARP1 for human, rat and mouse have highly conserved sequence. Overall folding of PARP1, PARP2 and PARP4 confirms similarity in catalytic domains but can differ in substrate proteins. The three-dimensional structure of PARP4 was interacted with NAD using the molecular docking method and the interaction sites were determined. When we modeled the three-dimensional structure of PARP4 using MODELLER v9.22 algorithm and examined the interaction with Autodock v4.2 in computer environment, we observed that the enzyme is connected with a common motif similar to PARP1 and PARP2. When PARP1 and PARP2 interact with this common motif with NAD, we experimentally observed that these structures interact directly with NAD in order to undergo catalytic reactions by Thermal-Shift assay. The PARP4-NAD complex with the binding energy -26.73 kJ/mol was further used for molecular dynamics analysis. Root mean square deviation (RMSD) for all backbone atoms, electrostatic energy, van der Waals energy of PARP4-NAD complex were studied in the form of molecular dynamics trajectories to throw light on the medically important PARP family of enzymes.