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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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    Noncovalent Pyrene-Polyethylene Glycol Coatings of Carbon Nanotubes Achieve in Vitro Biocompatibility
    (AMER CHEMICAL SOC, 2018) Meran, Mehdi; Akkus, Pelin Deniz; Kurkcuoglu, Ozge; Baysak, Elif; Hizal, Gurkan; Haciosmanoglu, Ebru; Unlu, Ayhan; Karatepe, Nilgun; Guner, F. Seniha
    Single-walled carbon nanotubes (SWNTs) have become increasingly exploited in biological applications, such as imaging and drug delivery. The application of SWNTs in biological settings requires the surface chemistry to remain through the low solubility in aqueous media. In this research, a facile approach for the preparation of a polyethylene glycol (PEG)-coated SWNT-based nanocarrier was reported. We focused on the effect of PEG chain length and SWNT size on the cytotoxicity of PEG coated SWNTs as a superior drug delivery nanovector. First, all-atom molecular dynamics (MD) simulations were employed to explore the stability and behavior of SWNT/pyrene-PEG (SWNT/Pyr-PEG) structures at a molecular level that is not attainable with experiments. The MD studies revealed that (i) a pi-pi stacking interactions between the pyrene bearing PEG molecules and SWNTs are maintained in bulky situations, regardless of PEG molecular weight or SWNT size; (ii) pyrene molecules diffuse over the SWNT surface without detaching; and (iii) both short and long dynamic Pyr-PEG chains have the capability of effectively coating the SWNT surface. In light of the simulations, noncovalent (pi-pi stacking) assemblies of SWNT/Pyr-PEG with different molecular weights of PEG (M-W = 2000, 5000, and 12000) were successfully fabricated and characterized. For longer PEG chains, more effective coating of SWNTs was obtained, resulting in more biocompatible SWNT/Pyr-PEG nanomaterials. The number of SWNTs coated by Pyr-PEG was highly dependent on the length of pyrene bearing PEG polymers. Moreover, the short SWNTs showed a higher amount of PEG coating with respect to the long SWNTs. Cell viability results demonstrated a dose-dependent cytotoxicity of coated SWNTs. Short SWNTs coated with longer PEG chains have low cytotoxicity to be used in in vivo studies.