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    Discriminative sensing of DOPA enantiomers by cyclodextrin anchored graphene nanohybrids
    (Elsevier Science Bv, 2017) Ates, Salih; Zor, Erhan; Akin, Ilker; Bingol, Haluk; Alpaydin, Sabri; Akgemci, Emine G.
    Discriminative sensing of chiral species with a convenient and robust system is a challenge in chemistry, pharmaceutics and particularly in biomedical science. Advanced nanohybrid materials for discrimination of these biologically active molecules can be developed by combination of individual obvious advantages of different molecular scaffolds. Herein, we report on the comparison of the performance of cyclodextrin functionalized graphene derivatives (x-CD/rGO, x: alpha-, beta-, gamma-) for discrimination of DOPA enantiomers. Within this respect, electrochemical measurements were conducted and the experimental results were compared to molecular docking method. Thanks to cavity size of g-CD and the unique properties of graphene, rGO/gamma-CD nanohybrid is capable of selective recognition of DOPA enantiomers. Limit of detection (LOD) value and sensitivity were determined as 15.9 mu M and 0.2525 mu A mu M-1 for D- DOPA, and 14.9 mu M and 0.6894 mu A mu M-1 for L-DOPA. (C) 2017 Elsevier B.V. All rights reserved.
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    Graphene-based hybrid for enantioselective sensing applications
    (Elsevier Advanced Technology, 2017) Zor, Erhan; Morales-Narvaez, Eden; Alpaydin, Sabri; Bingol, Haluk; Ersoz, Mustafa; Merkoci, Arben
    Chirality is a major field of research of chemical biology and is essential in pharmacology. Accordingly, approaches for distinguishing between different chiral forms of a compound are of great interest. We report on an efficient and generic enantioselective sensor that is achieved by coupling reduced graphene oxide with gamma-cyclodextrin (rGO/gamma-CD). The enantioselective sensing capability of the resulting structure was operated in both electrical and optical mode for of tryptophan enantiomers (D-/L-Trp). In this sense, voltammetric and photoluminescence measurements were conducted and the experimental results were compared to molecular docking method. We gain insight into the occurring recognition mechanism with selectivity toward D- and L-Trp as shown in voltammetric, photoluminescence and molecular docking responses. As an enantioselective solid phase on an electrochemical transducer, thanks to the different dimensional interaction of enantiomers with hybrid material, a discrepancy occurs in the Gibbs free energy leading to a difference in oxidation peak potential as observed in electrochemical measurements. The optical sensing principle is based on the energy transfer phenomenon that occurs between photo excited D-/L-Trp enantiomers and rGO/gamma-CD giving rise to an enantioselective photoluminescence quenching due to the tendency of chiral enantiomers to form complexes with gamma-CD in different molecular orientations as demonstrated by molecular docking studies. The approach, which is the first demonstration of applicability of molecular docking to show both enantioselective electrochemical and photoluminescence quenching capabilities of a graphene-related hybrid material, is truly new and may have broad interest in combination of experimental and computational methods for enantiosensing of chiral molecules. (C) 2016 Elsevier B.V. All rights reserved.
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    Nanopaper-based photoluminescent enantioselective sensing of L-Lysine by L-Cysteine modified carbon quantum dots
    (Elsevier Science Sa, 2019) Copur, Funda; Bekar, Nisa; Zor, Erhan; Alpaydin, Sabri; Bingol, Haluk
    The production and application of chiral nanomaterials are expanding to understand the nature of chiral interactions and to detect chiral molecules due to the chirality is a fundamental characteristics of life processes. With the new advances in optical sensors by combining the advantages of optical signaling unit and sensing platform, new avenues can be opened to produce simple and useful devices for chiral sensor applications. Here, we report construction of nanoscale chirality of carbon quantum dots (CQDs) by functionalization with L-cysteine and application for paper-based sensors. Within this respect, nanopaper made of cellulose nanofibers was prepared and the produced chiral carbon quantum dots (cCQDs) were embedded into nanopaper to gain photoluminescence properties. The chiral sensing behavior of cCQDs was investigated in solution phase and nanopaper. cCQDs exhibited an enantioselective response towards L-lysine among the tested enantiomers of amino acids with a LOD value of 0.30 mM and 0.97 mM for solution phase and nanopaper, respectively.
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    Photoluminescent nanopaper-based microcuvette for iodide detection in seawater
    (Elsevier Science Sa, 2018) Zor, Erhan; Alpaydin, Sabri; Arici, Aylin; Saglam, Muhammed Esad; Bingol, Haluk
    Nanopaper defined as a sheet made of cellulose nanofibers has recently attracted a growing interest in paper-based flexible and transparent sustainable transistors, electronics, devices and sensors. Use of bacterial cellulose nanopaper, particularly in optical sensing platforms, is becoming increasingly popular owing to its numerous desirable properties. Herein, we propose a carbon quantum dots embedded paper-based sensor for selective iodide sensing. To this aim, the nanopaper was obtained by an environment-friendly approach using bacterial cellulose made of nanofibers (the diameter of nanofibers was observed as 40 +/- 10 nm), which were produced by A. xylinum. Then, nitrogen-doped carbon quantum dots were embedded into nanopaper to gain photoluminescence properties. The obtained photoluminescent nanopaper was cut into circular pieces for easily handling, or rectangular pieces for use in a disposable wax-printed paper-based microcuvette which could be inserted in a common spectrofluorometer. Finally, the nanopaper pieces were used for anion sensing and we obtained a selective detection of iodide in seawater (as a model real sample media). Limit of detection (LOD) and limit of quantification (LOQ) values were respectively calculated as 48 and 144 mu M (6.1 and 18.3 ppm) for microcuvette application in seawater. (C) 2017 Elsevier B.V. All rights reserved.
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    A reduced graphene oxide/?-cyclodextrin hybrid for the detection of methionine: electrochemical, fluorometric and computational studies
    (Royal Soc Chemistry, 2014) Zor, Erhan; Saglam, Muhammed Esad; Alpaydin, Sabri; Bingol, Haluk
    We report on fluorometric and voltammetric detection of L-methionine (Met) based on host-guest interactions between Met and reduced graphene oxide/alpha-cyclodextrin (rGO/alpha-CD) hybrid materials. For voltammetric measurements, rGO/alpha-CD was used as an electrode modification material and successful detection of Met was achieved. Also, rGO/alpha-CD was used as a fluorescence quencher (turn off) for luminol which was employed as a fluorescent probe. The addition of Met into the same solution gave rise to fluorescence enhancement (turn on) after the host-guest recognition between Met and rGO/alpha-CD which caused the release of luminol. Interactions of luminol and Met with rGO/alpha-CD were modeled by molecular docking using AutoDock Vina and the interaction energies were predicted to be -4.3 and -4.4 kcal mol(-1), respectively. The proposed biosensor is considered to be a promising model for the detection of Met.