Browsing by Author "Thirumalaivasan, Natesan"

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A far-red to NIR emitting ultra-sensitive probe for the detection of endogenous HOCl in zebrafish and the RAW 264.7 cell line
(2019-04-14)
Natarajan, Vijay
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Thirumalaivasan, Natesan
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Wu, Shu-Pao
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Sivan, Velmathi
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應用化學系
Fluorescence imaging is a dynamic tool for monitoring the functions of biomolecules in living systems. Probes with emission in the far-red to near-infrared range have been found to demonstrate great application prospects in bioimaging due to their deep tissue penetration, low background fluorescence, minimum photodamage to the tissue and high sensitivity. The present study aimed to construct a far-red to near-infrared emitting probe (PI) bearing dicyanoisophorone coupled with a phenothiazine moiety. The probe exhibits an instant response towards HOCl with a colour change from red to yellow with a 100 fold fluorescence enhancement at 620 nm with a low detection limit (42 nM). The electron-rich sulfur atom can be oxidised by HOCl; this endows the probe with distinct selectivity over other anions as well as other reactive oxygen species. The probe demonstrates great cell permeability with low toxicity to the cell. Therefore, the probe can be effectively applied in biological systems to monitor the endogenous level of HOCl produced by PMA in living systems and in the fluorescence imaging of endogenous HOCl in zebrafish and the RAW 264.7 cell line.
A fluorescent turn-on probe for detection of hypochlorus acid and its bioimaging in living cells
(2020-06-05)
Chu, Chien-Ju
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Wu, Guan-Syuan
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Ma, Ho-I
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Venkatesan, Parthiban
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Thirumalaivasan, Natesan
Hypochlorous acid has played several functions in the biological system. However, excess HOCI can cause damage to biomolecules and result in some diseases. Accordingly, a new fluorescent probe, BSP, has been developed for fast recognition of HOCI through the HOG-induced oxidation of methyl phenyl sulfide to sulfoxide. The reaction of BSP with HOG caused a 22-fold fluorescence enhancement (quantum yield increase from 0.006 to 0.133). The detection limit of HOCI is found to be 30 nM (S/N = 3). The fluorescence enhancement is due to the suppression of the photo-induced electron transfer from the methyl phenyl sulfide moiety to BODIPY. Eventually, the cellular fluorescence imaging experiment showed that BSP could be effectively used for monitoring HOCI in living cells. (C) 2020 Elsevier B.V. All rights reserved.
A highly selective fluorescent anthracene-based chemosensor for imaging Zn2+ in living cells and zebrafish
(2020-05-01)
Minh-Hai Nguyen
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Thi-Nguyet Nguyen
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Danh-Quang Do
;
Hung-Huy Nguyen
;
Quan-Manh Phung
A new fluorescent chemosensor (An3) bearing anthracenyl rings was designed and developed for detection of Zn2+. Addition of Zn2+ into An3 gave rise to a fluorescent turn-on response at 424 nm whereas Al3+, Cd (2+), Co2+, Cu2+, K+, Mg2+, Zn2+, Ca2+, Fe3+, Mn2+, Ni2+, Pb2+, and Hg2+ did not induce any emission intensity enhancement. Furthermore, the probe exhibited high selectivity toward Zn2+ and a very low detection limit (36 nM) based on chelation-enhanced fluorescence. Theoretical calculations revealed the possible formation of 1:1 and 1:2 complexes between An3 and Zn2+. In bioimaging experiments, the chemosensor displayed low cytotoxicity and good biocompatibility, rendering it an effective tool for fluorescent visualization of Zn2+ in living cells and zebrafish models.
A hydrogen sulfide triggered self-immolative fluorescent probe for lysosome labeling in live cells
(2018-02-07)
Velusamy, Nithya
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Thirumalaivasan, Natesan
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Bobba, Kondapa Naidu
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Wu, Shu-Pao
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Bhuniya, Sankarprasad
We developed a naphthalimide-based, lysosome-targeting, and self-immolative fluorescent probe for H2S detection. Probe LS-1 comprises a 2-formylbenzoate derivative of the 1,8-naphthalimide fluorophore. H2S forms a thiohemiacetal intermediate by reacting with the formyl group of the 2-formylbenzoate derivative, which subsequently undergoes intramolecular cyclization with the ester moiety to generate a free naphthalimide fluorophore (FL-1). The UV-vis absorbance (lambda(abs)) value of probe LS-1 at 450 nm increased in the presence of H2S. Similarly, with increasing H2S concentrations, the emission band (lambda(em)) centered at 560 nm increased gradually. The probe was found to be highly sensitive and chemoselective towards H2S compared with other biological analytes. Probe LS-1 was nontoxic and very stable across the physiological pH range. The probe LS-1 enables the detection of intracellular endogenous H2S formation in HT29 cells in lysosomes.
A nano-molar fluorescent turn-on probe for copper(II) detection in living cells
(2019-09-15)
Wei, Ling-Fang
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Chen, Chong-Yan
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Lai, Chia-Kai
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Thirumalaivasan, Natesan
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Wu, Shu-Pao
The development of fluorescent probes to detect trace metal ions in biological samples has been in great need. Herein, a fluorescence turn-on sensor (PHC) was designed for highly selective detection of Cu2+ ions. The probe PHC shows weak fluorescence due to imine isomerization. With Cu2+, a significant blue emission due to Cu2+-induced oxidation of imine to a carboxylate group is observed. The turn-on process is observed with a 63-fold increase of fluorescence quantum yield (from 0.004 to 0.252). The emission intensity has a good linear relation at Cu2+ concentrations of 0-40 mu M. The detection limit is estimated as 8 nM (S/N = 3). The maximum emission change induced by Cu2+ is found in the pH range of 6.5-8.0. The probe PHC can be applied in detecting Cu2+ in living cells monitored by confocal fluorescence microscopy imaging.
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.
Coumarin-based Hg2+ fluorescent probe: Fluorescence turn-on detection for Hg2+ bioimaging in living cells and zebrafish
(2019-08-05)
Chen, Chong-Guang
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Vijay, Natarajan
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Thirumalaivasan, Natesan
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Velmathi, Sivan
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Wu, Shu-Pao
The need in developing fluorescent probes for trace metal ion detection in biological samples has been an important issue. Herein, a reaction-based fluorescent probe PIC containing a perimidine moiety was designed and synthesized for Hg2+ detection. The probe can selectively distinguish Hg2+ with 42-fold fluorescent enhancement from the other metal ions at physiological pH. This probe can detect Hg2+ with the detection limit of 1.08 mu M. The sensor PIC can be applied to real-time detection of Hg2+ in cells with blue emission. (C) 2019 Elsevier B.V. All rights reserved.
Cysteamine-capped gold-copper nanoclusters for fluorometric determination and imaging of chromium(VI) and dopamine
(2019-12-01)
Shellaiah, Muthaiah
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Simon, Turibius
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Thirumalaivasan, Natesan
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Sun, Kien Wen
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Ko, Fu-Hsiang
Highly emissive cysteamine-capped gold-copper bimetallic nanoclusters (CA-AuCu NCs) with a quantum yield of 18% were synthesized via one-pot anti-galvanic reduction. The CA-AuCu NCs were characterized by HR-TEM, XPS, FTIR, MALDI-TOF mass spectrometry, DLS, and zeta potential analyses. The NCs are shown to be viable fluorescent probes for Cr(VI) ions and dopamine (DA) via quenching of the blue fluorescence, typically measured at excitation/emission wavelengths of 350/436 nm. During DA recognition, a dark brown color appears, which is distinguishable from that of Cr(VI) detection. The aggregation induced quenching due to electron transfer was demonstrated by photoluminescence, HR-TEM, FTIR, DLS, and zeta potential interrogations. In buffer of pH 7, response is linear in the 0.2 100 mu M for Cr(VI) and from 0.4 250 mu M for DA. The respective detection limits are 80 and 135 nM. The method was applied to the determination of both Cr(VI) and DA in (spiked) tap, lake and sea water, and in human urine samples. The low toxicity of CA-AuCu NCs was validated by the MTT assay, and their responses to Cr(VI) ions and DA was also proven by Raw 264.7 cell imaging. Graphical abstract Cysteamine capped Au-Cu nanoclusters (CA-AuCu NCs) were synthesized via one-pot anti-galvanic reduction and utilized in sensing of Cr(VI) ions and dopamine (DA) with demonstrated real/urine and cell imaging applications.
Fluorescent coumarin-based probe for cysteine and homocysteine with live cell application
(2017-08-05)
Wei, Ling-Fang
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Thirumalaivasan, Natesan
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Liao, Yu-Cheng
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Wu, Shu-Pao
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應用化學系
Cysteine (Cys) and homocysteine (Hcy) are two of important biological thiols and function as important roles in several biological processes. The development of Cys and Hcy probes will help to explore the functions of biothiols in biological systems. In this work, a new coumarin-based probe AC, containing an acryloyl moiety, was developed for Cys and Hcy detection in cells. Cys and Hcy undergo a nucleophilic addition and subsequent cyclization reaction to remove to the acryloyl group and yield a fluorescent product, 7-hydroxylcomuarin. The probe AC showed good selectivity for cysteine and homocysteine over glutathione and other amino acids and had low detection limits of 65 nM for Cys and 79 nM for Hcy, respectively. Additionally, confocal imaging experiments demonstrated that the probe AC can be applied to visualize Cys and Hcy in living cells. (C) 2017 Elsevier B.V. All rights reserved.
FRET-based dual channel fluorescent probe for detecting endogenous/exogenous H2O2/H2S formation through multicolor images
(2019-02-01)
Velusamy, Nithya
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Thirumalaivasan, Natesan
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Bobba, Kondapa Naidu
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Podder, Arup
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Wu, Shu-Pao
We have developed a FRET-based fluorescent probe (PHS1) as a combination of two different fluorophores (coumarin and naphthalimide); which can detect both exogenous and endogenous H2S and H2O2 in live cells through multicolor images. The precise overlap between UV-absorption of naphthalimide and the emission band of coumarin in probe PHS1 allows the acquisition of the self-calibrated information of dual analytes through FRET-based imaging. The UV-Vis absorption (lambda(abs) 390 nm) and fluorescence emission (lambda(em) 460 nm) of probe PHS1 in the presence of H2O2 are increased similar to 35-fold and similar to 15-fold respectively. It also allows the estimation of the levels of H2S through enhancement of emission intensity at 550 nm. The probe PHS1 exhibits high stability against various analytes, including various pH (4-9.5). The cell viability assay data indicate that the probe is not harmful to the cancer cells. The nontoxic nature of the probe PHS1 encourages application for cancer cell labeling. The probe PHS1 can detect the level of endogenous H2O2, H2S, and H2O2/H2S in cancer cells through blue, green and FRET-based green channel imaging. PHS1 is a unique probe, has potential application for diagnosing cancer by providing information on the level of dual analytes (H2S, H2O2) in cancer cells.
Highly selective turn-on probe for H2S with imaging applications in vitro and in vivo
(2017-11-21)
Thirumalaivasan, Natesan
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Venkatesan, Parthiban
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Wu, Shu-Pao
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應用化學系
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Department of Applied Chemistry
Hydrogen sulfide (H2S) is the third endogenous gaseous signaling molecule, and its distribution affects several biological processes. To clarify the roles of H2S in living systems, the exact determination of H2S in living cells in vivo has become an important issue. Herein, we report a novel pyrene-based fluorescent probe, PyN3, as a H2S turn-on sensor via reduction of azide to amine, which subsequently undergoes self-immolation through intramolecular 1,6-elimination of the rho-aminobenzyl moiety, releasing 1-aminopyrene and leading to the recovery of fluorescence intensity. With its high sensitivity, good selectivity, and low cytotoxicity, PyN3 was able to recognize both exogenous and endogenously produced H2S in biological systems. In contrast to the traditional azide-based H2S probes, PyN3 shows efficient and effective selectivity to H2S at biological pH ranges. Because of these promising properties, PyN3 is an excellent probe for visualizing endogenous H2S in vitro and in vivo.
Multi-Stimuli Responsive FRET Processes of Bifluorophoric AlEgens in an Amphiphilic Copolymer and Its Application to Cyanide Detection in Aqueous Media
(2020-03-04)
Nhien, Pham Quoc
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Chou, Wei-Lun
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Cuc, Tu Thi Kim
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Khang, Trang Manh
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Wu, Chia-Hua
A novel amphiphilic aggregation-induced emission (AIE) copolymer, that is, poly(NIPAM-co-TPE-SP), consisting of N-isopropylacrylamide (NIPAM) as a hydrophilic unit and a tetraphenylethylene-spiropyran monomer (TPE-SP) as a bifluorophoric unit is reported. Upon UV exposure, the close form of non-emissive spiropyran (SP) in poly(NIPAM-co-TPE-SP) can be photo-switched to the open form of emissive merocyanine (MC) in poly(NIPAM-co-TPE-MC) in an aqueous solution, leading to ratiometric fluorescence of AlEgens between green TPE and red MC emissions at 517 and 627 nm, respectively, via Forster resonance energy transfer (FRET). Distinct FRET processes of poly(NIPAM-co-TPE-MC) can be observed under various UV and visible light irradiations, acid-base conditions, thermal treatments, and cyanide ion interactions, which are also confirmed by theoretical studies. The subtle perturbations of environmental factors, such as UV exposure, pH value, temperature, and cyanide ion, can be detected in aqueous media by distinct ratiometric fluorescence changes of the FRET behavior in the amphiphilic poly(NIPAM-co-TPE-MC). Moreover, the first FRET sensor polymer poly(NIPAM-co-TPE-MC) based on dual AlEgens of TPE and MC units is developed to show a very high selectivity and sensitivity with a low detection limit (LOD = 0.26 mu M) toward the cyanide ion in water, which only contain an approximately 1% molar ratio of the bifluorophoric content and can be utilized in cellular bioimaging applications for cyanide detections.
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.
New phenazine based AIE probes for selective detection of aluminium(III) ions in presence of other trivalent metal ions in living cells
(2017-12-21)
Balamurugan, Gopal
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Velmathi, Sivan
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Thirumalaivasan, Natesan
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Wu, Shu Pao
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應用化學系
Phenazine fluorophore based imidazole derivatives (S1 and S2) were synthesized and sensor studies were carried out with various cations. Aggregation induced emission (AIE) was observed selectively for Al3+ among other cations under study in case of both sensors. H-1 NMR titration supported the aggregation induced emission of S2 with Al3+. ESI mass spectra successfully confirmed the aggregate formation. SEM images clearly showed the aggregation of receptor induced by Al3+ in a flower-like fashion. AIE probe was successfully applied for bio-imaging of RAW264.7 cells.