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    Cytotoxic effect of silica nanoparticles on human retinal pigment epithelial cells
    (Academic Press Inc Elsevier Science, 2023) Kaynar, Ayse Humeyra; Comelekoglu, Ulku; Kibar, Deniz; Yildirim, Metin; Yildirimcan, Saadet; Yilmaz, Sakir Necat; Erat, Selma
    In recent years, the use of nanotechnology-based methods has become widespread in the treatment of ocular diseases. Silica nanoparticles (SiO2 NPs) are most common used NPs in medical field due to their physicochemical properties. SiO2 NPs can easily cross biological membranes and interact with basic biological structures, causing structural and functional changes in cells. In this study, it was aimed to investigate the dose dependent effect of SiO2 NPs on retinal pigment epithelium (RPE) in vitro using electrobiophysical, biochemical and histological methods. A commercially purchased human RPE (hARPE-19) cell line was used in this study. Cells were divided into four groups as control, 50 mg/mL SiO2, 100 mg/mL SiO2 and 150 mg/mL SiO2 groups. Cell index, apoptotic activity, cell cycle and oxidative stress markers were measured in all groups. Findings in the present study showed that SiO2 nanoparticles reduced cell proliferation, increased oxidative stress, apoptosis and arrest in the G0/G1 phase of the cell cycle as dose dependent manner in ARPE-19 cells. In conclusion, SiO2 exposure can induce cytotoxic effects in RPE cell line. The results of this study provide clues that exposure to SiO2 nanoparticles may impair visual function and reduce quality of life. However, further studies are needed in this regard.& COPY; 2023 Elsevier Inc. All rights reserved.
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    Solution-Processable Growth and Characterization of Dandelion-like ZnO:B Microflower Structures
    (Mdpi, 2022) Erat, Selma; Braun, Artur; Cetinkaya, Samed; Yildirimcan, Saadet; Kasapoglu, Ahmet Emre; Gur, Emre; Harputlu, Ersan
    Intrinsic and dandelion-like microflower nano-rod structures of boron-doped ZnO thin films were synthesized with an ecofriendly and cost-effective chemical bath deposition technique from an aqueous solution of zinc nitrate hexahdyrate [Zn(NO3)(2).6H(2)O] as a precursor solution and boric acid as a doping solution. The boron concentrations were 0.1, 0.3, 0.5, 1.0, 3.0, 5.0, and 7.0 by volume. Scanning electron micrographs showed that doping with boron appears to hinder the vertical alignment of crystallites. Additionally, independent hexagonal nano-rod structures were observed to coalesce together to form dandelion-like structures on the film's surface. The atomic ratio of the elements was determined via the X-ray photoemission spectrum technique. There were no substantial changes in the vibration structure of the film upon doping in terms of the Raman spectra. The optical band gap of ZnO (3.28 eV) decreased with B doping. The band gap of the ZnO:B film varied between 3.18 and 3.22 eV. The activation energy of the ZnO was calculated as 0.051 eV, whereas that of the ZnO:B film containing 1.0% B was calculated as 0.013 eV at low temperatures (273-348 K), versus 0.072 eV and 0.183 eV at high temperatures (348-523 K), respectively. Consequently, it can be interpreted that the 1% B-doped ZnO, which has the lowest activation energy at both low and high temperatures, may find some application areas such as in sensors for gases and in solar cells.
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    Öğe
    Study on crystallographic and electronic structure of micrometre-scale ZnO and ZnO:B rods via X-ray absorption fine-structure spectroscopy
    (Int Union Crystallography, 2021) Erat, Selma; Ozkendir, Osman Murat; Yildirimcan, Saadet; Gunaydin, Selen; Harfouche, Messaoud; Demir, Bunyamin; Braun, Artur
    X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS) spectra were recorded to investigate the electronic structure and local crystal structure of ZnO and ZnO:B powders produced via hydrothermal synthesis. ZnO and ZnO:B grow as micrometre-scale rods with hexagonal shape, as confirmed by scanning electron microscopy micrographs. The number of broken ZnO:B rods increases with increasing B concentration, as observed in the images, due to B atoms locating in between the Zn and O atoms which weakens and/or breaks the Zn-O bonds. However, no disorder within the crystallographic structure of ZnO upon B doping is observed from X-ray diffraction results, which were supported by EXAFS results. To determine the atomic locations of boron atoms in the crystal structure and their influence on the zinc atoms, EXAFS data were fitted with calculated spectra using the crystal structure parameters obtained from the crystallographic analysis of the samples. EXAFS data fitting and complementary k-weight analysis revealed the positions of the B atoms - their positions were determined to be in between the Zn and O atoms.