Browsing by Author "Naha, Sanay"

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A novel nanomolar highly selective fluorescent probe for imaging mercury (II) in living cells and zebrafish
(2018-12-20)
Liu, Yen-Yu
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Naha, Sanay
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Thirumalaivasan, Natesan
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Velmathi, Sivan
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Wu, Shu-Pao
A novel fluorescent probe, PES, which contains a bisethylsulfane moiety, displayed high specificity for Hg2+ detection. With Hg2+, PES showed significant blue fluorescence enhancement, while the metal ions Al3+, Ag+, Cr3+, Ca2+, Cu2+, Co2+, Cd2+, Fe3+, Fe2+, Mn2+, Mg2+, Ni2+, Zn2+, and Pb2+ exhibited only negligible fluorescence change. PES has been found to be an effective quantitative detector (LOD, 57 nM) for Hg2+ in semi-aqueous medium based on the Hg2+-induced removal of bisethylsulfane. It resulted in a turn-on blue fluorescence response. The fluorescence enhancement induced by Hg2+ was observed over the pH range of 4-10. Our fluorescence cell-imaging experiments revealed the applicability of the new probe, PES, to be a reliable and effective fluorescent marker for Hg2+ in living cells.
Nanomolar Detection of H2S in an Aqueous Medium: Application in Endogenous and Exogenous Imaging of HeLa Cells and Zebrafish
(2020-08-11)
Naha, Sanay
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Thirumalaivasan, Natesan
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Garai, Somenath
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Wu, Shu-Pao
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Velmathi, Sivan
The homeostasis of short-lived reactive species such as hydrogen sulfide/hypochlorous acid (H2S/HOCI) in biological systems is essential for maintaining intercellular balance. An unchecked increase in biological H2S concentrations impedes homeostasis. In this report, we present a molecular probe pyrenebased sulfonyl hydrazone derived from pyrene for the selective detection of H2S endogenously as well as exogenously through a "turn-off' response in water. The structure of the receptor is confirmed by Fourier-transform infrared spectroscopy, H-1 and C-13 nuclear magnetic resonance spectroscopy, electrospray ionization mass spectrometry, and single-crystal X-ray diffraction studies. The receptor shows excellent green emission in both the aqueous phase and solid state. Quenching of green emission of the receptor is observed only when H2S is present in water with a detection limit of 18 nM. Other competing anions and cations do not have any influence on the receptor's optical properties. The efficiency of H2S detection is not negatively impacted by other reactive sulfur species too. The sensing mechanism of H2S follows a chemodosimetric reductive elimination of sulfur dioxide, which is supported by product isolation. The receptor is found to be biocompatible, as evident by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and its utility is extended to endogenous and exogenous fluorescence imaging of HeLa cells and zebrafish.
Naphthalimide based smart sensor for CN-/Fe3+ and H2S. Synthesis and application in RAW264.7 cells and zebrafish imaging
(2020-03-01)
Naha, Sanay
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Wu, Shu-Pao
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Velmathi, Sivan
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應用化學系
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Department of Applied Chemistry
Achieving selective detection of target analytes in aqueous media continues to be an arduous proposition. Herein, we report the conceptualization and synthesis of a novel tailor-fit molecular probe R based on 1,8-naphthalimide which acts as a trifunctional molecular sensor for CN-, Fe3+ and H2S. R shows colorimetric and fluorometric "on-off" relay recognition for CN- (red colour and orange emission) and Fe3+ (no colour and no emission) in 5% H2O + DMSO medium which is experimentally ascertained to be a tandem deprotonation-protonation process and is supported by H-1-NMR titration. Among all RSS (Reactive Sulphur Species), R shows selectivity for H2S through red colouration. Other coexistent anions, cations and RSS cause no discernible perturbation to the detection process. The detection of H2S is attributed to a chemodosimetric reduction of the nitro to amino group as evidenced by a potentiometric titration assay. The experimental observations are well supported by DFT theoretical calculation. The K-a for CN-/Fe3+ are 1.4 x 10(4) M-1, 6.07 x 10(4) M-1 respectively and photochemical yield of R + CN- is 0.86. Limit of detections for CN-, Fe3+ and H2S are 17.5 nM, 8.69 mu M and 8.1 mu M respectively. Receptor R is effective for real time applications, bio-compatible and has been successfully employed for confocal fluorescence imaging of RAW264.7 cell and zebrafish.