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Öğe Amperometric glucose sensor based on the glucose oxidase enzyme immobilized on graphite rod electrode modified with Fe3O4-CS-Au magnetic nanoparticles(Springer Heidelberg, 2018) Onay, Aykut; Dogan, Uzeyir; Ciftci, Hakan; Cetin, Demet; Suludere, Zekiye; Tamer, UgurIn this report, an amperometric detection method for blood glucose level was developed benefiting from glucose oxidase (GO) enzyme immobilization on nanoparticle modified graphite rod (GR) electrode. Fe3O4-CS-Au magnetic nanoparticles were synthesized, characterized by TEM, UV-Vis, magnetometry, FTIR, and zeta potential measurements and used for the modification of GR electrode. This modified electrode was used for the detection of glucose level amperometrically at 0.6 V. The obtained calibration graph was linear in the range of 5-30mM glucose concentration with a coefficient of determination (R-2) 0.9971. The limit of detection (LOD) and limit of quantification (LOQ) values were calculated as 0.55 and 1.83mM, respectively. The modified GR electrode showed excellent selectivity in the presence of dopamine, ascorbic acid, and uric acid. The applicability of the developed method was examined in real blood samples by comparing the results obtained from commercial glucose sensor. This novel glucose detection method exhibited fast amperometric response, long storage time, and good selectivity.Öğe Cytotoxic, apoptotic and necrotic effects of starch coated copper nanoparticles on Capan 1 pancreatic cancer cells(Elsevier, 2023) Ilbasmis-Tamer, Sibel; Turk, Mustafa; Evran, Sefika; Boyaci, Ismail Hakki; Ciftci, Hakan; Tamer, UgurIn the present study we utilized a green synthesis approach by reduction route with ascorbic acid in the presence of starch as the capping agent. Here we aimed to generate a stable starch coating copper nanoparticles (Cu-SNPs) and to investigate their apoptotic and necrotic effects on Capan 1 pancreatic cancer cell line. The water soluble monodisperse starch-protected zero-valent copper nanoparticles were characterized by transmission electron microscopy, XPS, FTIR analysis. TEM images showed that the presence of metallic copper nanoparticles with anisotrophic morphologies and the sizes of 90% copper nanoparticles were in 50 nm and 80 nm range. Cetyl-trimethylammonium bromide (CTAB) coated copper nanoparticles was also synthesized to compare the stability of starch coating copper nanoparticles. It was also found that copper nanoparticles were significantly protected by starch coating. Cu-SNPs exhibited stronger antimicrobial effects on Staphylocossus and Enterococcus. In vitro cell culture studies demonstrated that Cu-SNPs were not cytotoxic on L929-fibroblasts and Capan 1 pancreatic cancer cell in all concentrations used here (6.25-100 ppm) in different extends. The cytotoxic, necrotic, and apoptotic effects of Cu-SNPs on the Capan 1 pancreatic cancer cell line have been exhibited. Furthermore, the micronucleus test and hemolytic activity test were also performed.Öğe Development of poly(3-aminophenylboronic acid) modified graphite rod electrode suitable for fluoride determination(Elsevier Science Bv, 2014) Ciftci, Hakan; Oztekin, Yasemin; Tamer, Ugur; Ramanaviciene, Almira; Ramanavicius, ArunasPoly(3-aminophenylboronic acid), (PAPBA) film was formed on the graphite rod surface by potential cycling. The PAPBA-modified graphite rod (PAPBA/GR) electrode prepared in this way was used for potentiometric fluoride determination. The linear calibration range was from 5 x 10(-4) to 5 x 10(-2) M with the slope of the linear part of the calibration curve of 42.5 mV/log C. No interference effect of the most common ions such as sodium, potassium, chloride, nitrate, iodide, calcium, zinc, aluminum, sulfate and sorbitol was observed during electrochemical determination of fluoride. On the other hand, the PAPBA/GR electrode showed not only good sensitivity and selectivity, but also relatively rapid response to changes of analyte concentrations in the range of 20 s. The sensor was successfully applied for fluoride determination in real sample - toothpaste. (C) 2014 Elsevier B.V. All rights reserved.Öğe Electrochemical biosensor based on glucose oxidase encapsulated within enzymatically synthesized poly(1,10-phenanthroline-5,6-dione)(Elsevier Science Bv, 2014) Ciftci, Hakan; Oztekin, Yasemin; Tamer, Ugur; Ramanaviciene, Almira; Ramanavicius, ArunasThis study is focused on the investigation of electrocatalytic effect of glucose oxidase (GOx) immobilized on the graphite rod (GR) electrode. The enzyme modified electrode was prepared by encapsulation of immobilized GOx within enzymatically formed poly(1,10-phenanthroline-5,6-dione) (pPD) film. The electrochemical responses of such enzymatic electrode (pPD/GOx/GR) vs. different glucose concentrations were examined chronoamperometrically in acetate-phosphate buffer solution (A-PBS), pH 6.0, under aerobic or anaerobic conditions. Amperometric signals of the pPD/GOx/GR electrode exhibited well-defined hyperbolic dependence upon glucose concentration. Amperometric signals at 100 mM of glucose were 41.17 and 32.27 mu A under aerobic and anaerobic conditions, respectively. Amperometric signals of the pPD/GOx/GR electrode decreased by 6% within seven days. The pPD/GOx/GR electrode showed excellent selectivity in the presence of dopamine and uric acid. Furthermore it had a good reproducibility and repeatability with standard deviation of 9.4% and 8.0%, respectively. (C) 2014 Elsevier B.V. All rights reserved.Öğe Electrochemical copper (II) sensor based on chitosan covered gold nanoparticles(Springer, 2014) Ciftci, Hakan; Tamer, Ugur; Metin, Aysegul U.; Alver, Erol; Kizir, NevinThis study outlines a new sensing platform based on glassy carbon electrodes modified by gold nanoparticles (AuNPs) for the determination of heavy metal. A glassy carbon electrode was modified by chitosan stabilized AuNPs. AuNPs were prepared by reducing gold salt with a polysaccharide chitosan. Here, chitosan acted as a reducing/stabilizing agent. The AuNPs were characterized with UV-Visible absorption spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Chitosan covered AuNPs were immobilized on the glassy carbon electrode for the determination of Cu (II) in aqueous solutions. The electrochemical determination of Cu (II) ions was performed using the differential pulse voltammetry technique. Some parameters for Cu (II) determination, such as pH, preconcentration time and electrolysis potential of Cu (II), were optimized. The detection limit was calculated as 5 x 10(-9) mol L-1 by means of the 3:1 current-to-noise ratio. The interference of Cr(III), Fe(II), Ni(II), Pb(II), Mg(II), Zn(II), Ba(II) ions was investigated and showed a negligible effect on the electrode response. Recovery studies were carried out using tap water.Öğe Electrochemical determination of iodide by poly(3-aminophenylboronic acid) film electrode at moderately low pH ranges(Elsevier, 2011) Ciftci, Hakan; Tamer, UgurA new potentiometric sensor for the determination of iodide based on poly(3-aminophenylboronic acid) (PAPBA) film electrode was constructed. Poly(3-Aminophenylboronic acid) films were synthesized electrochemically on platinum electrode by cyclic voltammetry. The effect of film thickness, pH, and preconditioning parameters on the electrode performance were examined. The analytical performance was evaluated and linear calibration graphs were obtained in the concentration range of 10(-6) to 10(-1) M iodide ion. The limit of detection was found to be 8 x 10(-7) M. The response time of the sensor was 5s and its lifetime is about one week. To check the selectivity of the PAPBA film for iodide ion, potential interferences such as Cl-, Br-, F-, CN-, IO3-, Ca-2(+), and Mg-2(+) were tested. The PAPBA electrode was also employed as a sensing platform for the determination of iodide ions in commercial table salt. (C) 2010 Elsevier B.V. All rights reserved.Öğe Fabrication and characterization of gold-nanoparticles/chitosan film: a scaffold for L929-fibroblasts(Taylor & Francis Ltd, 2013) Turk, Mustafa; Tamer, Ugur; Alver, Erol; Ciftci, Hakan; Metin, Aysegul U.; Karahan, SiyamiThe objective of the present study was to fabricate a gold nanoparticle crosslinked chitosan (Ch/AuNPs) composite film simple and to evaluate its use as a carrier matrix for L929-fibroblasts. L929-fibroblasts were seeded either onto Ch or Ch/AuNPs scaffolds. The Ch/AuNPs scaffold exhibited a higher cell proliferation and growth rate. The cytotoxicity test determined trypan blue staining indicated that Ch scaffolds devoid of AuNPs expressed almost no toxicity while the Ch/AuNPs composite scaffolds expressed a very limited toxicity only at higher doses. The Ch/AuNPs scaffold promotes cell attachment, growth and proliferation with almost no cytotoxicity.Öğe Functional gold nanorod particles on conducting polymer poly(3-octylthiophene) as non-enzymatic glucose sensor(Elsevier Science Bv, 2012) Ciftci, Hakan; Tamer, UgurThe immobilization of surface-functionalized self-assembled monolayer (SAM) gold nanoparticles onto poly(3-octylthiophene) (POT) was achieved by the cooperation of hydrophobic forces. SAMs were prepared by 11-mercaptoundecanoicacid (MUA), 4-mercaptophenyl boronic acid (MPB), and 1-decanethiol (DT) hydrophobic substrates. Nanoparticles-SAM-POT system was characterized by cyclic voltammetry, SEM. EDAX and contact angle measurements. SAMs (MUA) is closely packed providing effective blocking of the underlying platinum electrode and preventing a ferrocyanide molecule from penetrating. However, potential scanning was applied at SAMs (MUA) modified electrode on which electron penetrating holes or defects were occured. Since SAMs (MPB) is poorly packed according to SAMs (MUA), ferrocyanide molecules could penetrate to SAMs (MPB) modified electrode surface. POT-Au-SAM (MPB) electrode was used for glucose determination as potentiometric non-enzymatic glucose sensor. The analytical performance was evaluated and linear calibration graphs were obtained in the concentration range of 5-30 mM glucose including the level of human blood glucose. (C) 2011 Elsevier Ltd. All rights reserved.Öğe Glucose determination based on a two component self-assembled monolayer functionalized surfaceenhanced Raman spectroscopy (SERS) probe(Royal Soc Chemistry, 2014) Torul, Hilal; Ciftci, Hakan; Dudak, Fahriye Ceyda; Adiguzel, Yekbun; Kulah, Haluk; Boyaci, Ismail Hakki; Tamer, UgurIn this report, we present a new detection method for blood glucose, using gold nanorod SERS, a surface enhanced Raman scattering probe embedded in two component self-assembled monolayers (SAMs). Gold nanorod particles and a gold coated slide surface were modified with the two component SAMs consisting of 3-mercaptophenylboronic acid (3-MBA) and 1-decanethiol (1-DT). The immobilization of 3-MBA/1-DT surface-functionalized gold nanoparticles onto 3-MBA/1-DT modified gold-coated slide surfaces was achieved by the cooperation of hydrophobic forces. Two component SAM functionalized substrates were used as SERS probes, by means of the boronic acid and the alkyl spacer functional groups that serve as the molecular recognition and penetration agents, respectively. The SERS platform surface was characterized by cyclic voltammetry, contact angle measurements, AFM (atomic force microscopy) and Raman spectroscopy. Optimum values of the parameters such as pH, time and (3-MBA/1-DT) molar ratio were also examined for the glucose determination. The analytical performance was evaluated and linear calibration graphs were obtained in the glucose concentration range of 2-16 mM, which is also in the range of the blood glucose levels, and the detection limit was found to be 0.5 mM. As a result, the SERS platform was also used for the determination of glucose in plasma samples.Öğe High-yield aqueous synthesis of multi-branched iron oxide core-gold shell nanoparticles: SERS substrate for immobilization and magnetic separation of bacteria(Springer, 2014) Tamer, Ugur; Onay, Aykut; Ciftci, Hakan; Bozkurt, Akif Goktug; Cetin, Demet; Suludere, Zekiye; Greneche, Jean-MarcThe high product yield of multi-branched core-shell Fe3-x O-4@Au magnetic nanoparticles was synthesized used as magnetic separation platform and surface-enhanced Raman scattering (SERS) substrates. The multi-branched magnetic nanoparticles were prepared by a seed-mediated growth approach using magnetic gold nanospheres as the seeds and subsequent reduction of metal salt with ascorbic acid in the presence of a stabilizing agent chitosan biopolymer and silver ions. The anisotropic growth of nanoparticles was observed in the presence of chitosan polymer matrix resulting in multi-branched nanoparticles with a diameter over 100 nm, and silver ions also play a crucial role on the growth of multi-branched nanoparticles. We propose the mechanism of the formation of multi-branched nanoparticles while the properties of nanoparticles embedded in chitosan matrix are discussed. The surface morphology of nanoparticles was characterized with transmission electron microscopy, scanning electron microscopy, ultraviolet visible spectroscopy (UV-Vis), X-ray diffraction, and fourier transform infrared spectroscopy and Fe-57 Mossbauer spectrometry. Additionally, the magnetic properties of the nanoparticles were also examined. We also demonstrated that the synthesized Fe3-x O-4@Au multi-branched nanoparticle is capable of targeted separation of pathogens from matrix and sensing as SERS substrates.Öğe Multiwalled Carbon Nanotube-Chitosan Scaffold: Cytotoxic, Apoptotic and Necrotic Effects on Chondrocyte Cell Lines(Bentham Science Publ Ltd, 2017) Ilbasmis-Tamer, Sibel; Ciftci, Hakan; Turk, Mustafa; Degim, Tuncer; Tamer, UgurBackground: Carbon nanotubes (CNTs) have been considered highly successful and proficient in terms of their mechanical, thermal and electrical functionalization and biocompatibility. In regards to their significant extent in bone regeneration, it has been determined that CNTs hold the capability to endure clinical applications through bone tissue engineering and orthopedic procedures. In the present study, we report on a composite preparation, involving the use of CNT-chitosan as scaffold for bone repair and regeneration. Through the use of water-soluble tetrazolium salt (WST-1) and double staining methods, the cytotoxic, necrotic, and apoptotic effects of chitosan-multiwalled carbon nanotube nanocomposites on the chondrocyte ATTC cell line have been exhibited. Methods: The chitosan-multiwalled carbon nanotube scaffolds were prepared. Chondrocytes differentiation tool (ATCC) cell line was prepared. WST-1 assay for cytotoxicity studies were performed by using chondrocytes cells in 12.5-200 mu L concentration range. The samples of membranes (chitosan-multiwalled carbon nanotube scaffold) were measured at 2 mg/mL and further prepared amongst chitosan-multiwalled carbon nanotube scaffold's which were placed into separate wells. While in the process of incubation, in the four-hour time range, the plates were immediately read in an Elisa microplate Reader. To predict the number of apoptotic and necrotic cells in culture, the technique of double staining with Hoechst dye was performed with PI on the basis of scoring cell nuclei. The mechanical properties such as tensile strength and elongation at break values of the chitosan only and chitosan/CNT scaffolds were evaluated on Texture Analyzer. Results: Based on the results of the WST-1 assay procedure, the amount of cell viability was not significantly affected by nanocomposite concentrations and the lowest mortality rate of cells was obtained at a concentration of 12.5 mu g/mL, whereas the highest mortality rate was obtained at a rate of 200 mu g/mL. In addition, the effects of chitosan-CNT nanocomposites were not found to cytotoxic on chondrocyte cells. The double staining method has been able to determine the apoptotic and necrotic effects of chitosan MWCNT nanocomposites. The apoptotic and necrotic effects of the combined compounds had varied within the concentrations. In a similar manner to the outcome of the control groups, apoptosis was obtained at a percentage of 2.67%. Under a fluorescent inverted microscope, the apoptotic cell nuclei were stained with a stronger blue fluorescence in comparison to non-apoptotic cells, which may have had an effect. We also compared the strain-stress curve measurements results. The results indicated that the mechanical properties of scaffold were not different. Elongation at break values increased by addition of CNT. Conclusion: CNTs as a biomaterial hold the potential to be used for applications in future regenerative medicine. By using the components of chondrocytes (ATTC) cell lines, the cytotoxicity evaluations were made for the chitosan-multiwalled carbon nanotube scaffold. The chitosan-MWCNT nanocomposites do not seem to induce drastic cytotoxicity to the chondrocyte cells.Öğe Nanoparticle embedded chitosan film for agglomeration free TEM images(Wiley-Blackwell, 2017) Dogan, Uzeyir; Ciftci, Hakan; Cetin, Demet; Suludere, Zekiye; Tamer, UgurTransmission electron microscopy (TEM) is a very useful and commonly used microscopy technique, used especially for the characterization of nanoparticles. However, the identification of the magnetic nanoparticle could be thought problematic in TEM analysis, due to the fact that the magnetic nanoparticles are usually form aggregates on the TEM grid to form bigger particles generating higher stability. This prevents to see exact shape and size of each nanoparticle. In order to overcome this problem, a simple process for the formation of well-dispersed nanoparticles was conducted, by covering chitosan film on the unmodified copper grid, it was said to result in aggregation-free TEM images. It is also important to fix the magnetic nanoparticles on the TEM grids, due to possible contamination of TEM filament which is operated under high vacuum conditions. The chitosan film matrix also helps to protect the TEM filament from contact with magnetic nanoparticles during the imaging process. The proposed procedure offers a quick method to fix the nanoparticles in a conventional copper TEM grid and chitosan matrix prevents agglomeration of nanoparticles, and thus getting TEM images showing well-dispersed individual nanoparticles.Öğe Non-enzymatic sensing of glucose using a glassy carbon electrode modified with gold nanoparticles coated with polyethyleneimine and 3-aminophenylboronic acid(Springer Wien, 2016) Ciftci, Hakan; Alver, Erol; Celik, Filiz; Metin, Aysegul U.; Tamer, UgurA non-enzymatic electrochemical method was developed for sensing glucose by using a glassy carbon electrode modified with 3-aminophenylboronic acid (APBA) immobilized on polyethyleneimine (PEI)-coated gold nanoparticles. The modified electrode was characterized by TEM, zeta potential measurements and UV-Vis spectroscopy. Its analytical performance was evaluated in pH 9 solution by potentiometry. The respective calibration plot, established at open circuit potential (vs. Ag/AgCl) covers the 0.5-50 mM glucose concentration range, which makes it suitable for blood glucose assays. The detection limit is 0.025 mM, and no interference is caused by ascorbic acid, dopamine, and uric acid. Effects of other carbohydrates such as fructose, galactose and saccharose were also investigated. The electrode was used to determine glucose in human serum samples and the results agreed well with those obtained with commercial amperometric enzymatic sensors.Öğe Silver nanoparticles: cytotoxic, apoptotic, and necrotic effects on MCF-7 cells(Tubitak Scientific & Technical Research Council Turkey, 2013) Ciftci, Hakan; Turk, Mustafa; Tamer, Ugur; Karahan, Siyami; Menemen, YusufThe present study was conducted to examine cytotoxic, apoptotic, and necrotic effects of silver nanoparticles (AgNPs) on MCF-7 cells. Colloidal AgNPs were fabricated in an alkaline pH environment via reduction of silver nitrate with hydroxylamine hydrochloride. The size of AgNPs was measured by atomic force microscopy (AFM), transmission electron microscopy (TEM), and dynamic light scattering. Zeta potential of AgNPs was determined by laser Doppler microelectrophoresis. After exposing MCF-7 cells to AgNPs for 24 h, cytotoxicity was measured by WST-1 assay. Apoptosis and necrosis in MCF-7 cells were detected by Annexin-V-FLUOS immunostaining and double staining of Hoechst dye with propidium iodide. In AFM and TEM analyses, the sizes of AgNPs varied from 16 nm to 20 nm. AgNPs were 80 nm in hydrodynamic diameter with a zeta potential of -38.2 mV. The WST-1 assay resulted in an IC50 value of 40 mu g/mL. AgNPs caused apoptotic and necrotic effects in a dose-dependent manner The apoptotic effect of AgNPs was marked up to a concentration of 80 mu g/mL AgNPs. At higher concentrations, the apoptotic effect decreased while the necrotic effect became prominent. The results indicate that AgNPs with a zeta potential of -38.2 mV and hydrodynamic diameter of 80 nm can be used in vitro at concentrations of up to 40 mu g/mL.
