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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only Exploration of novel 6,8,9-trisubstituted purine analogues: synthesis, in vitro biological evaluation, and their effect on human cancer cells(Tubitak Scientific & Technological Research Council Turkey, 2024) Polat, Muhammed Fatih; Atalay, Rengul; Tuncbilek, Meral; N/A; Şahin, İrem Durmaz; Koç University Research Center for Translational Medicine (KUTTAM); School of MedicineCancer, a leading global cause of mortality, demands continuous advancements in therapeutic strategies. This study focuses on the design and synthesis of a novel series of purine derivatives, specifically 6 -(substituted phenyl piperazine)-8-(4-phenoxyphenyl)9-cyclopentyl purine derivatives (5-11). The motivation behind this endeavor lies in addressing acquired resistance mechanisms in cancer cells, a significant hurdle in current treatment modalities. The synthesis, starting from 4,6-dichloro-5-nitropyrimidine, involves a multi -step process, resulting in seven new purine derivatives. Biological evaluation against human liver, colon, and breast cancer cells (Huh7, HCT116, and MCF7, respectively) was performed using the SRB assay. Among the synthesized analogs, compounds 5 and 6, exhibited notable cytotoxic activity, surpassing clinically used positive controls 5-Fluorouracil and Fludarabine in terms of efficacy. This research underscores the potential of purine derivatives with a phenyl group at the C-8 position as a scaffold for developing compounds with improved anticancer properties. The findings offer insights for future exploration and development of novel agents in cancer pharmaceutical research.Publication Metadata only Targeting cancer cells via tumor-homing peptide CREKA functional PEG nanoparticles(Elsevier, 2016) N/A; N/A; N/A; Department of Chemical and Biological Engineering; Okur, Aysu Ceren; Erkoç, Pelin; Kızılel, Seda; Master Student; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 28376Targeting cell microenvironment via nano-particle based therapies holds great promise for treatment of various diseases. One of the main challenges in targeted delivery of nanoparticles for cancer therapy includes reduced localization of delivery vehicles at tumor site. The therapeutic efficacy of drugs can be improved by recruiting delivery vehicles towards specific region of tumorigenesis in the body. Here, we demonstrate an effective approach in creating PEG particles via water-in-water emulsion technique where tumor-homing peptide CREKA was used for functionalization. Simultaneous conjugation of laminin peptide IKVAV into hydrogel network and influence of altered combinations of ligands on intracellular uptake of anticancer drugs by HeLa cells were investigated. CREKA conjugated hydrogel nanoparticles were more effective to improve apoptotic effects of the model drug Doxorubicin (DOX) compared to that of particles conjugated with other peptides. Fluorescence intensity analysis on confocal micrographs suggested significantly higher cellular uptake of CREKA conjugated PEG particles than internalization of nanoparticles in other groups. We observed that fibrin binding ability of PEG particles could be increased up to 94% through CREKA conjugation. Our results suggest the possibility of cancer cell targeting via CREKA-functional PEG nanoparticles.Publication Metadata only Biomedical optical fibers(Royal Soc Chemistry, 2021) Jiang, Nan; Yetişen, Ali K.; N/A; N/A; Department of Mechanical Engineering; Sarabi, Misagh Rezapour; Öztürk, Ece; Taşoğlu, Savaş; PhD Student; Faculty Member; Faculty Member; Department of Mechanical Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); KU Arçelik Research Center for Creative Industries (KUAR) / KU Arçelik Yaratıcı Endüstriler Uygulama ve Araştırma Merkezi (KUAR); Graduate School of Sciences and Engineering; School of Medicine; College of Engineering; N/A; 326940; 291971Optical fibers with the ability to propagate and transfer data via optical signals have been used for decades in medicine. Biomaterials featuring the properties of softness, biocompatibility, and biodegradability enable the introduction of optical fibers' uses in biomedical engineering applications such as medical implants and health monitoring systems. Here, we review the emerging medical and health-field applications of optical fibers, illustrating the new wave for the fabrication of implantable devices, wearable sensors, and photodetection and therapy setups. A glimpse of fabrication methods is also provided, with the introduction of 3D printing as an emerging fabrication technology. The use of artificial intelligence for solving issues such as data analysis and outcome prediction is also discussed, paving the way for the new optical treatments for human health.Publication Metadata only Performance of high capacity Li-ion pouch cells over wide range of operating temperatures and discharge rates(Elsevier Science Sa, 2020) N/A; N/A; N/A; Department of Chemical and Biological Engineering; Alipour, Mohammad; Esen, Ekin; Varzeghani, Amir Rahimi; Kızılel, Rıza; PhD Student; PhD Student; PhD Student; Researcher; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; 114475Operating temperature of Lithium-ion batteries (LIBs) significantly affects their electrochemical-thermal performance, cycle life, and cost. This study presents the thermal and electrochemical performance of 20 Ah LiFePO4 cells for 8 current rates (0.2C-5C) at 8 operating temperatures (-20 degrees C to 50 degrees C). Results show that the effects of operating temperature and current rate on cell performance differ above 10 degrees C, between 10 degrees C and 0 degrees C, and at subzero temperatures. Based on the electrochemical impedance spectroscopy (EIS) measurements, significantly higher bulk and charge-transfer resistances in conjunction with the lower diffusion coefficients results in poor battery efficiency at subzero temperatures. Optimum operating condition is 50 degrees C at a rate of 0.2C, in terms of utilized power and capacity, while a considerable power loss and capacity decrease occur below 20 degrees C. Furthermore, increasing the current rate is detrimental above 0 degrees C, whereas it improves cell performance at -10 degrees C, in terms of cell capacity. Moreover, cell temperature reaches an undesirable value at 50 degrees C and 5C rate, thus a thermal management system is necessary for high capacity LiFePO4 cells at higher temperatures and/or at higher C-rates. Additionally, temperature differences on the surface of high capacity cells reach 10 degrees C below room temperature at high current rates which can lead to nonuniform material utilization, and consequently cell failures. Finally, the cycle life of 20 Ah LiFePO4 cells decreases dramatically as discharge current rate increases. (C) 2020 Elsevier B.V. All rights reserved.Publication Metadata only Determination of thyroglobulin levels by radioimmunoassay method in anti thyroglobulin positive differentiated thyroid patients: one center clinical experience(Pergamon-Elsevier Science Ltd, 2020) Uçar, Burcu; Şen, Melis; Acar, Tayfun; N/A; Demirkol, Mehmet Onur; Faculty Member; School of Medicine; 196946It is very crucial to determine Tg accurately and precisely in thyroid cancer cases. Although there are many studies on the detection of Tg in thyroid cases in the literature, there are no sufficient clinical studies examining many cases with different features by using RIA methodology. Here, a radiometric and chromatographic method has been studied for the first time to eliminate the interference from anti-Tg positive patients. In this paper, radioimmunoassay (RIA) and immunoradiometric (IRMA) techniques were used for the analysis of 302 sera collected from patients for Tg and TgAb quantification. By the RIA technique, a reliable result was obtained by calculating the real Tg value quantitatively in 41 patients showing TgAb positivity out of 208 patients. Our findings show that the RIA assay is the most suitable approach for detection of changeable (low or undetectable) Tg value and metastases detected by post-therapeutic imaging in early-stage DTC cases showing preoperative and postoperative TgAb positivity. The new immunoradiometric method allows the real (%) Tg value to be reached in a part of TgAb-positive DTC. Even if TgAb positive in the metastatic and nonmetastatic DTC patient group. This allows the accurate clinical follow-up of patients.Publication Metadata only Antibacterial silicone-urea/organoclay nanocomposites(Springer, 2009) Department of Chemistry; N/A; N/A; Department of Chemistry; Yılgör, Emel; Nugay, Işık Işıl; Bakan, Murat; Yılgör, İskender; Researcher; Undergraduate Student; Undergraduate Student; Faculty Member; Department of Chemistry; College of Sciences; College of Engineering; College of Engineering; College of Sciences; N/A; N/A; N/A; 24181Montmorillonite modified with distearyldimethyl ammonium chloride (C18-QAC) (Nanofil-15) (NF15) was incorporated into polydimethylsiloxane-urea (silicone-urea, PSU) copolymers. PSU was obtained by the reaction of equimolar amounts of aminopropyl terminated polydimethylsiloxane (PDMS) oligomer (= 3,200 g/mol) and bis(4-isocyanatohexyl) methane (HMDI). A series of PSU/NF15 nanocomposites were prepared by solution blending with organoclay loadings ranging from 0.80 to 9.60% by weight, corresponding to 0.30 to 3.60% C18-QAC. Colloidal dispersions of organophilic clay (NF15) in isopropanol were mixed with the PSU solution in isopropanol and were subjected to ultrasonic treatment. Composite films were obtained by solution casting. FTIR spectroscopy confirmed that the organoclay mainly interacted with the urea groups but not with PDMS. XRD analysis showed that nanocomposites containing up to 6.40% by weight of organoclay had fully exfoliated silicate layers in the polymer matrix, whereas 9.60% loading had an intercalated structure. Physicochemical properties of nanocomposites were determined. PSU/NF15 nanocomposites displayed excellent long-term antibacterial properties against E. coli.Publication Metadata only Nanoheterogeneous ZrTa metallic glass thin films with high strength and toughness(Elsevier, 2022) Behboud, Ali B.; Ozerinc, Sezer; N/A; Motallebzadeh, Amir; Researcher; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; N/AThis study investigated the mechanical behavior of ZrxTa1-x (x = 21-79 at%) thin films and nanolayered films of ZrTa with modulated composition as model systems to gain insight into the hardness and toughness of metallic glasses and metallic glass nanocomposites. The monolithic films exhibit two primary micro-structures, namely, a fully amorphous form (Zr = 35-70at%.) and an amorphous-crystalline composite (21-30 at% Zr). The amorphous films show a monotonic hardness variation with composition over a wide range of 5.5 - 9 GPa. The partial crystallization of the films results in a further jump in hardness, as opposed to the general trend of softening upon crystallization. The emergence of the crystalline phase also improves the ductility of the films, as verified by nanoindentation-based fracture toughness measurements. The indentation pile-up exhibits several shear bands in the fully amorphous films, replaced by a featureless pileup zone for the case of Zr25Ta75, further verifying the superior toughness of the composite. The second part of the analysis pursued obtaining a similar toughening through fully amorphous nanolayered films of Zr35Ta65 / Zr70Ta30. The results indicate that these films provide a balanced combination of high hardness and enhanced ductility, providing an alternative route to the development of tough metallic glass coatings. Data Availability: The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.Publication Metadata only Motion of single terrylene molecules in confined channels of poly(butadiene)-poly(ethylene oxide) diblock copolymer(Amer Chemical Soc, 2009) N/A; Department of Physics; Department of Chemistry; Yorulmaz, Mustafa; Kiraz, Alper; Demirel, Adem Levent; Master Student; Faculty Member; Faculty Member; Department of Physics; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; 22542; 6568The motion of terrylene probe molecules in confined PB channels of an asymmetric PB-PEO diblock copolymer has been investigated by single molecule tracking. The one-dimensional diffusion coefficients were found to be significantly smaller and had a narrower distribution compared to two-dimensional diffusion coefficients in PB. The trajectories of some single molecules showed unusual behavior of directed motion where mean square displacement had a parabolic dependence oil lag time. The likely origin of this behavior is discussed in terms of local variations in the PB channel width and the resulting change in the local density. The results show the effect of nonuniformities and heterogeneities in the channels on the motion of single molecules and demonstrate the sensitivity of single molecule tracking in characterizing self-assembled block copolymer morphologies.Publication Metadata only Investigation of the factors affecting the photothermal therapy potential of small iron oxide nanoparticles over the 730-840 nm spectral region(Royal Soc Chemistry, 2018) N/A; N/A; N/A; Department of Physics; Department of Chemistry; Bilici, Kübra; Muti, Abdullah; Duman, Fatma Demir; Sennaroğlu, Alphan; Acar, Havva Funda Yağcı; PhD Student; PhD Student; PhD Student; Faculty Member; Faculty Member; Department of Physics; Department of Chemistry; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; N/A; 23851; 178902The use of superparamagnetic iron oxide nanoparticles (SPIONs) as a sensitizer in photothermal therapy (PTT) is relatively new and the origin of such a phenomenon is not known. Usually, large crystals and aggregated particles are preferred in the literature, suggesting that these increase the absorbance of particles at the irradiation wavelength, and hence, provide a larger temperature increase. This study has two major goals: identification of the key factors that affect the photo-induced temperature increase in well-controlled experiments and the influence of laser irradiation on nanoparticle properties. Small, biocompatible poly(acrylic acid) coated SPIONs (PAA/SPIONs) were used since they are more practical for future medical use than large aggregates. We studied the impact of three major laser-dependent variables, namely the wavelength (between 728 and 838 nm), intensity (1.85-9.76 W cm(-2)) and power (105-800 mW) as well as attenuation at the irradiation wavelength, on photothermal heating achieved with PAA/SPIONs. Within the studied range of these variables, only the laser power plays a critical role on the magnitude of photothermal heating in solutions. There is no strong correlation between the attenuation at the excitation wavelength and the temperature increase. In addition, extensive characterization of SPIONs before and after irradiation revealed no significant difference, which supports the re-usability of SPIONs. Lastly, the PTT potential of these small PAA/SPIONs was demonstrated in vitro on HeLa cells. At these low laser powers no temperature increase in SPION-free water or cell death in SPION-free cells was detected. Hence, this study provides a new insight into the photothermal effect of SPIONs, provides a clear and repeatable experimental procedure and demonstrates great potential for small SPIONs to be exploited in PTT.Publication Metadata only Reversible switching of wetting properties and erasable patterning of polymer surfaces using plasma oxidation and thermal treatment(Elsevier Science Bv, 2018) Soydan, Seren; Jonas, Alexander; N/A; Department of Chemistry; N/A; Department of Chemistry; Department of Physics; Department of Chemistry; Rashid, Muhammed Zeeshan; Atay, İpek; Yağcı, Mustafa Barış; Yılgör, Emel; Kiraz, Alper; Yılgör, İskender; PhD Student; Post Doctorate Student; Researcher; Researcher; Faculty Member; Faculty Member; Department of Physics; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; N/A; College of Sciences; College of Sciences; College of Sciences; College of Sciences; N/A; N/A; N/A; N/A; 40527; 22542; 24181Polymer surfaces reversibly switchable from superhydrophobic to superhydrophilic by exposure to oxygen plasma and subsequent thermal treatment are demonstrated. Two inherently different polymers, hydrophobic segmented polydimethylsiloxane-urea copolymer (TPSC) and hydrophilic poly(methyl methacrylate) (PMMA) are modified with fumed silica nanoparticles to prepare superhydrophobic surfaces with roughness on nanometer to micrometer scale. Smooth TPSC and PMMA surfaces are also used as control samples. Regardless of their chemical structure and surface topography, all surfaces display completely reversible wetting behavior changing from hydrophobic to hydrophilic and back for many cycles upon plasma oxidation followed by thermal annealing. Influence of plasma power, plasma exposure time, annealing temperature and annealing time on the wetting behavior of polymeric surfaces are investigated. Surface compositions, textures and topographies are characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and white light interferometry (WLI), before and after oxidation and thermal annealing. Wetting properties of the surfaces are determined by measuring their static, advancing and receding water contact angle. We conclude that the chemical structure and surface topography of the polymers play a relatively minor role in reversible wetting behavior, where the essential factors are surface oxidation and migration of polymer molecules to the surface upon thermal annealing. Reconfigurable water channels on polymer surfaces are produced by plasma treatment using a mask and thermal annealing cycles. Such patterned reconfigurable hydrophilic regions can find use in surface microfluidics and optofluidics applications. (C) 2018 Elsevier B.V. All rights reserved.