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  • br Introduction br Selenium is well renowned as


    1. Introduction
    Selenium is well-renowned as an operational 64480-66-6 in the solar cells, semi-conductor devices, and photographic exposure meters. Its uniqueness lies in the special physical properties such as high aniso-tropy of thermal conductivity, optical conductivity, and X-ray sensing responses [1,2]. In the current decade, selenium nanoparticles (SeNPs) have reported significant medical diagnostic applications because of their minimal risk when compared to selenium alone, thus were effi-ciently employed as dietary supplements and as antioxidants [3]. Generally, the common industrial techniques employed in the synthesis of selenium nanomaterials involve complex mechanisms associated with huge environmental risks like high pressure and temperature [1]. However, recent literature reported about the green synthesis of metal nanoparticles through the advancement of morphology and size of nanoparticles [4,5]. Additionally, various microorganisms like bacteria, fungi, and yeast are also being used to reduce toxic metal ions into definite nanoscale particles [1,2]. For instance, the formation of silver nanoparticles by means of Escherichia coli was earlier reported by
    Natarajan et al. group [6] while Zare et al. have described a synthetic approach to prepare spherical selenium particles using Aspergillus ter-reus [7]. Fesharaki et al. have proposed a novel technique to recover selenium nanoparticles mediated by Klebsiella pneumonia [8]. More-over, many studies demonstrated amomentous toxicity difference be-tween SeNPs and selenium oxyanions such as selenite [9]. Selenite has the ability to obstruct the growth and even instigates liver toxicity, despite of its antioxidant nature [10]. Therefore, SeNPs with extremely minimal toxicity and significant antioxidant properties can be an ap-propriate option in order to regulate proper body functioning. Inter-estingly, there are also numerous reports that signified the anti-carci-nogenic influence of SeNPs against various types of cancers, thus elevating its potential [11,12].
    With the intent to explore the anti-carcinogenic effect of selenium nanoparticles against lung cancer, selenium nanoparticles were bio-synthesized and thus obtained SeNPs were characterized to study their morphology. Further, the SeNPs were evaluated for their cytotoxic potential in the presence and absence of X-rays against A549 cell lines and the results were discussed.
    Corresponding author at: No. 222, Department of Oncology, The First Affiliated Hospital of Dalian Medical University, Zhongshan Road, Dalian 116011, PR China.
    E-mail address: [email protected] (J. Liu).
    1 Contributed equally for this work.
    Available online 11 December 2018
    2. Experiments
    Sodium selenite (Na2SeO3, ≥97%, Chemical grade) was purchased from Shandong West Chemical Industry Co., Ltd. (China). Ascorbic acid (Vc), metformin hydrochloride, and Vitamin E (VE) were obtained from Sangon Biotech Co., Ltd. (Shanghai, China), acetic acid (HAc), and sodium hydroxide (NaOH) were acquired from Chengdu Kelong Chemical Reagent Plant (China).
    2.2. Preparation of Selenium Nanoparticles
    250 ml Erlenmeyer flask was used to harvest the bacterial seed cul-ture in 100 ml N-broth growth medium and incubated at 30 °C for about 24 h. 3 mM Sodium selenite (0.0518 g) and activated E.coli culture (1 ml) and were inoculated into 100 ml sterilized N-broth medium, placed in an incubator at 30 °C for 48 hat 150 rpm. UV visible (HACH, DR 5000, USA) spectrophotometer was employed to analyze the samples. The mixture was centrifuged at 12,000 rpm for 10 min to isolate the particles from the reaction mixture and then washed thrice using acetone and distilled water. For control experiment, active E.coli culture was autoclaved for 15 min and cultivated into 100 ml sterilized N-broth medium with 3 mM (0.0518 g) sodium selenite under similar conditions as described above.
    2.3. Characterization
    Transmission electron microscopy (TEM, Zeiss-EM10C) was em-ployed to study the dimension and morphology of the synthesized SeNPs at a raising voltage of 80 kv. Ultraviolet visible (UV–vis) spec-trophotometer at a resolution of 2 nm was used to record the absorption spectra at a wave length range of 200–1000 nm. For the elemental analysis of the product, Energy dispersive X-ray analysis (EDAX) ana-lyzer (JSM-7600F, JEOL, Japan) was used. XRD analysis (Xpert pro, PANalytical, Holland) was performed to investigate the crystalline phase of synthesized selenium nanoparticles.
    2.4. Cell Culture and Cytotoxicity Study
    Roswell Park Memorial Institute (RPMI-1640) medium was used to cultureA549 cells and supplemented with 10% fetal bovine serum (FBS) along with 1% antibiotic mixture of Penicillin-Streptomycin. The cells were further incubated under 5% CO2 and 37 °C standard conditions. Then, the cells were grown in the desired culture medium and later incubated. MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) assay was employed to determine their cytotoxicity. Each well of 96-well plate was seeded with about 10,000 cells and incubated for 24 h. Later, various concentrations of SeNPs were used for the cells treatment in the presence and absence of X-ray and incubated for 24 h. Finally, MTT solution was used to treat the cells and incubated for 3 h followed by the addition of DMSO and rested for 15 min. ELISA mi-croplate reader (DYNEX, USA) was used to measure the absorbance at 570 nm. Clinac IX 6 MeV beam linear accelerator (Varian Medical Systems, Palo Alto, CA, USA) was used to administer the radiotherapy in vitro.