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    MerR-fluorescent protein chimera biosensor for fast and sensitive detection of Hg2+ in drinking water
    (Wiley, 2019) Ozyurt, Canan; Ustukarci, Handan; Evran, Serap; Telefoncu, Azmi
    Mercury ion (Hg2+) is a universal pollutant and its detection is crucial for public healthcare. In this study, we developed a novel fluorescent biosensor by construction of a protein fusion between the mercury-sensing transcription factor MerR and enhanced yellow fluorescent protein (EYFP). Hg2+-induced conformational change of MerR was transduced into fluorescence signal. Fluorescence intensity of the biosensor protein decreased with increasing concentrations of Hg2+ and a linear response was obtained in the range of 0.5-40 nM. The limit of detection was 0.5 nM, which was much lower than the maximum allowed level in water. The biosensor specificity was highly dependent on type and concentration of metal ion. The biosensor exhibited high specificity in a mixture of metal ions at 0.5 nM concentration. However, the interference effect was more pronounced at 40 nM concentration of metal ions. The measurement was completed in less than 1 Min with no need for sample preparation or preincubation steps. The biosensor achieved accurate and reliable detection in the spiked drinking water sample, as validated by the inductively coupled plasma optical emission spectrometry.
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    Nucleic Acid and Peptide Aptamers as Potential Antiviral Drugs
    (Bentham Science Publishers, 2021) Evran, Serap; Uğurlu, Özge; Man, Ezgi; Gültan, Merve; Özyurt, Canan
    Aptamers with target-specific binding properties have emerged as an alternative to antibodies. Nucleic acid aptamers are short single-stranded oligonucleotides that can fold into unique three-dimensional structures. Nucleic acid aptamers are selected from random libraries in vitro by using the SELEX (Systematic Evolution of Ligands by Exponential Enrichment) technology. Likewise, peptide aptamers are short peptides that can be selected in vitro by using different strategies including phage display, ribosome display, or mRNA display. Aptamers are superior to antibodies with regard to ease of production, high stability, small size, and low cost. Therefore, aptamers find broad use in different biotechnological and therapeutic applications. Among them, aptamer use in virus detection and antiviral therapy is one of the attractive applications. The present Covid-19 pandemic and life-threatening viral infections reveal the need for rapid therapeutic solutions that can efficiently target viral mechanisms. In this respect, the chapter is mainly focused on aptamers with antiviral activity, as well as the use of aptamers in viral detection platforms. First, we summarize aptamer selection technologies that can be performed in vitro. Among them, we briefly explain ribosome display, mRNA display and SELEX (Systematic Evolution of Ligands by Exponential Enrichment) technologies. Then, we review aptamers targeting viral proteins and viral invasion mechanisms. In addition, we give an overview of aptamers developed against viruses. We also discuss the major hurdles in aptamer use, as well as the strategies to improve the drug potential of aptamers. © 2021 Bentham Science Publishers.
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    Single-stranded DNA (ssDNA) Aptamer targeting SipA protein inhibits Salmonella Enteritidis invasion of intestinal epithelial cells
    (Elsevier, 2020) Shatila, Fatima; Yalcin, H. Tansel; Ozyurt, Canan; Evran, Serap; Cakir, Busra; Yasa, Ihsan; Nalbantsoy, Ayse
    Salmonella Enteritidis is an important pathogen that can invade the intestinal cells of its host causing salmonellosis. SipA protein, an effector protein secreted by T3SS, maintains invasion of host cells more efficient. Thus, inhibitory aptamers against SipA protein were developed using magnetic bead-based Systematic Evolution of Ligands by Exponential Enrichment (SELEX) method. The enriched sequences were obtained after 9 SELEX rounds. Among which, an aptamer namely Apt17 displayed Kd values equivalent to 114.9 and 63.4 nM at 27 degrees C and 37 degrees C, respectively. The effect of Apt17 on adhesion and invasion of Caco-2 cells by the tested strains was determined. While the adhesion and invasion of Salmonella Enteritidis TM 6 were inhibited by 70% and 37.7%, those of Salmonella Enteritidis TM 68 were inhibited by 45.71% and 39.5% respectively. These results represent a corner stone for future studies that could aim to develop putative inhibitors against Salmonellosis. (C) 2020 Elsevier B.V. All rights reserved.