A coumarin-based turn-on chemosensor for selective detection of Zn(II) and application in live cell imaging

Journal Pre-proof A coumarin-based turn-on chemosensor for selective detection of Zn(II) and application in live cell imaging Shang Yanfang, Wang Hualai, Bai Hui PII:

S1386-1425(19)31136-9

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https://doi.org/10.1016/j.saa.2019.117746

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SAA 117746

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Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

Received Date: 19 September 2019 Revised Date:

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Accepted Date: 1 November 2019

Please cite this article as: S. Yanfang, W. Hualai, B. Hui, A coumarin-based turn-on chemosensor for selective detection of Zn(II) and application in live cell imaging, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2019), doi: https://doi.org/10.1016/j.saa.2019.117746. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier B.V.

A Coumarin-based turn-on chemosensor for selective detection of Zn(II) and application in live cell imaging Shang Yanfang*, [a] [a]

Wang Hualai[a]

Bai Hui*, [b]

School of Chemistry and Chemical Engineering, Nantong University, Nantong, 226019, [email protected]

[b]

Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024; [email protected]

Graphical abstract

A new “turn-on” chemodosimeter exhibited instant / reversible and excellent specificity towards Zn2+ in aqueous media and living cells.

A Coumarin-based turn-on chemosensor for selective detection of Zn(II) and application in live cell imaging Shang Yanfang*, [a] Wang Lanping*, [b] Wang Wenling[b] Wang Hualai[a] [a]

School of Chemistry and Chemical Engineering, Nantong University, Nantong, 226019, People’s Republic of China; [email protected]

[b]

School of marine and Biological Engineering, Yancheng Teachers University, Yancheng, 224002, People’s Republic of China; [email protected]

Abstract: A 2-oxo-2H-chromene-3-carbohydrazide (CHB) was synthesized by the reaction of salicylaldehyde with diethyl malonate. The recognition behaviors of CHB to Zn2+ were investigated and the results showed that CHB exhibits well selectivity and sensitivity to Zn2+ with fast response in PBS (pH = 7.24, 60% DMF), the co-existed cations and anions could not interfere the recognition between CHB and Zn2+. Besides, the detection limit of CHB for Zn2+ was calculated to be 0.95 μM. Furthermore, DFT, EI-MS data and Job's plot were applied for determining the sensing mechanism of CHB with Zn2+ and the results showed that a type of 2:1 complex was formed between CHB and Zn2+ with the binding constant was 1.32×104 M-2. At last, probe CHB was successfully applied for the imaging of Zn2+ in living cells. Keywords: Cell imaging, Coumarin-based, DFT Study, Zn2+, Recognition Mechanism Introduction As essential trace elements, some transition-metal ions were widely existed in biological systems. Among these transition-metal ions, Zn2+ has been well considered as an important divalent ion and played a vital role in all kinds of basic physiological processes[1] including gene expression, cell growth, cell division[2], cellular metabolism[3], DNA replication and repair[4], neurotransmission modulator[5]. It is pointed out that nearly thousands of proteins contain zinc and over 200 enzymes are associated with zinc as a catalytic factor or a structural element[6, 7]. Some diseases were induced by disruptions of zinc homeostasis[8]. For instance, the deficiency of Zn2+ may lead to diminishing cognition, immune malfunction,

while excessive Zn2+ amount has been related to several neurological diseases, including Alzheimer's disease[9], prostate cancer, diabetes and cardiovascular diseases[10-13]. It has been reported that the normal content of Zn2+ in human plasma is 6 -12mM[8]. What’s more, the plants, the activity of reducing protective enzyme and photosynthesis could be infected by the high concentration of Zn2+ in the environment[14, 15]. So the development of techniques and tactics for exploring the trafficking of Zn2+ in biological processes was still an important and challenging topic. Due to the selectively recognize guest species with high selectivity, sensitivity, the fluorescent probes/chemosensors simplicity attracted particular attention for chemists [16-20]. A fluorescent probe/chemosensor is a molecular system for which the physicochemical properties change after interacting with chemical substances to produce detectable fluorescent signals[21]. Metal cation fluorescent chemical sensors have attracted wide attention because of their important role in medical biological systems and environment[22, 23]. A serious of fluorescence-based approaches for Zn(II) detection has been reported, including fluorescein, rhodamine, azo and coumarin[24-32]. Although various of probes are effective for detecting biological samples, arguably all suffer from one or more insufficients, which stimulates the search for development new Zn(II) imaging tools. Due to the long excitation wavelength, easily to be modifiable, low toxicity and photo-stable properties[33], large Stokes shift [34, 35], excellent quantum yields[36], high dipole moment of the excited state[33, 37], coumarin and its derivatives are widely used in medicine[38], pharmaceutical industry[39], food controls[40], materials[41]. Here, we developed a coumarin derivative CHB to examine the Zn2+ through metal-binding properties. The feasibility of using the CHB as an intracellular sensor of Zn2+ was examined by confocal fluorescence microscope. In our recently study, a new coumarin-based CHB for fast detection of Zn2+ was synthesized and characterized. Metal ion identification experiments showed that the probe exhibited a highly selective fluorescence enhancement recognition of Zn2+. Moreover, the selectivity of probe CHB toward Zn2+ comparing to other metal ions and anion is also

investigated. And the proposed mechanism of interaction was supported with DFT and ESI-MS. Experimental Materials and Instrumentation All reagents and solvents (analytical grade and spectroscopic grade) this communication mentioned being received from Shanghai, China. Most of metal ions solution were developed with their chloride salts. 1H NMR and

13

C NMR spectra were consulted on a

Bruker DRX 400 spectrometer relative to TMS for dissolving in DMSO-d6. Absorption spectra were measured by an UV-1800 ENG spectrometer. Emission spectra were determined on a RF-5301 fluorescence spectrophotometer. Elemental analysis was calculated through a VARI-EL elemental analyzer. Electrospray ionization mass spectra were collected by Triple TOF TM 5600+ system instrument. Synthesis of Probe CHB Scheme 1 explains the synthetic route of Probe CHB. Following the early reported methods, in ethanol solution containing 2-hydroxybenzaldehyde (1.22 g, 10 mmol) added diethyl malonate (0.190 mL, 10 mmol), adding the morpholine as the catalyzer, reflexed for about 6 h, white ethyl 2-oxo-2H-chromene-3-carboxylate was achieved and washed with ethanol for three times. Then ethyl 2-oxo-2H-chromene-3-carboxylate (0.654 g, 3 mmol) was added to a solution of Hydrazine hydrate in ethanol (30 mL) and stirred for 6 h. The yellow solid was separated, filtered and washed repeatedly with CH3OH and diethyl ether, and recrystallized from CH3CH2OH. The purity of CHB was further checked by TLC analysis (Yield: 76%). m.p. 176-178℃; Exact mass for CHB: 204.0535, ESI - MS ( positive mode ) [ CHB + 2H2O + H+ ]+ ( m / z, cal. 241.0824; Exp. 240.9237 ), [ CHB + 2CH3OH + 2H2O + Na+ ]+ ( m / z, Cal. 327.1168; Exp. 326.9625 ). Elemental analysis ( calcd. % ) for C10H8N2O3: C, 58.82; H, 3.95; N, 13.72; Found: C, 58.78; H, 4.04; N, 13.72. 1H-NMR (400 MHz, MeOD) δ 9.76 (s, 1H), 7.80-7.75 (m, 2H), 7.25-7.20 (m, 2H), 6.94-6.90 (m, 2H), 6.79-6.74 (m, 2H), 5.27 (s, 1H), 4.88 (s, 3H), 3.31 (dt, J = 3.2, 1.6 Hz, 1H). 13C-NMR (101 MHz, MeOD) δ 157.51 (s), 132.05 (s), 129.43 (s), 128.68 (s), 127.39-127.19 (m), 115.64 (s), 114.42 (s).

Scheme 1 here Results and discussion Synthesis and characterization of CHB The target coumarin derivative CHB was synthesized according to the Scheme 1. The structure of CHB was well characterized by FT-IR spectra (IR) analysis, Elemental analyses (EAs), 1H-NMR, 13C-NMR and Electrospray ionization mass spectra (ESI-MS) (Figures. S1-S4). The detailed information was described in the Supporting Information. The selectivity of CHB over alot of metal ions was determined in various different solvents, such as the pH range from 2.0 to 12.0 PBS buffer solutions with proportionate of CH3CH2OH or CH3OH or CH3CN or DMSO or DMF. Upon addition of Zn2+ ions into PBS (pH = 7.24, 60 % DMF) containing 5.0 μM CHB, a strong selective characteristic emission band was observed at 505 nm concomitantly a color change from colorless to greenish blue while the equivalent other metal ions did not induce significant fluorescence enhancement (as showed in Figure. 1). In other words, CHB can

be

used

to

sense

the

Zn2+

through

the

fluorescence

emission

in

PBS (pH = 7.24, 60 % DMF). Figure. 1 here. Fluorescence Response of CHB to Zn2+ To further demonstrate the sensing ability to Zn2+ of the CHB, it was titrated with incremental amount of Zn2+ ions and the response of CHB was recorded by fluorescence measurement. It displays in Figure. 2 that the change in fluorescence spectra of CHB upon titration with Zn2+ ions. With the increase of Zn2+ concentrations, the fluorescence emission of CHB at 505 nm steadily increased following colorless changed to greenish blue under the UV-light illuminated. The fluorescence quantum yields (φf)[42] of CHB and CHB-Zn2+ were 0.024 and 0.526, respectively. The fluorescence enhancement phenomenon is caused by the inhibition of photoinduced electron transfer (PET), as showed in Scheme 2. These speculations are consistent with previous publishcations[43, 44].

Scheme 2 here

Figure. 2 here. Competition of CHB to Zn2+ with various metal ions For further develop the practical apply of CHB as a ion selective fluorescent probe for Zn2+, competition experiments were carried out in PBS (pH = 7.24, 60 % DMF) with CHB (5.0 μM) and 2 equiv. of Zn2+, followed by adding 5.0 equiv. of various metal ions including K+, Na+, Mg2+, Ca2+, Cr3+, and et al. The results showed that a obvious fluorescence enhancement was found when Zn2+ was added to CHB in presence of other metal cations in PBS (pH = 7.24, 60 % DMF). According to Figure. 3, tested metal ions except Zn2+ caused a negligible effect on the fluorescence intensity enhancement of the CHB- Zn2+ complexation at 505 nm, which revealed that CHB could detect Zn2+ ion selectively in a complex context of a potentially competing species. Figure. 3 here. UV-vis Spectra for Zn2+ In order to determine the sensitivity of the CHB towards Zn2+ ions, the UV–vis absorption titrations were independently carried out by successive addition of Zn2+ to the DMF of CHB. Figure. S5 displayed well-defined bands at 280 and 360 nm, respectively, which strengthened constantly by the rising concentration of Zn2+. When the concentration of Zn2+ up to 10 μM, the absorbance intensity almost arrived to saturate situation. Selectivity and anti-interference over other anions To investigate the anion whether interfere selectivity of the CHB to Zn2+, variation fluorescence spectra of the complex were taken in the presence of several anions, such as Cl-, Br-, I-, SO42-, PO43-, H2PO4-, OH-, HCO3-, NO3-, Br-, C2O42-, F-, HPO42-, S2O32-, NO2-, Ac-, P2O74-, B4O72-, HSO3-, SO32-. In Figure. 4, no significant fluorescent enhancement was generated after the addition of various anions. Furthermore, illustrated in Figure. 5 the emission intensity of CHB-Zn2+ complex had barely been affected by the presence of several anions above mentioned. These observations indicated that the CHB-Zn2+ complex had eminent selectivity and anti-interference ability over other anions.

Figure. 4 here. Figure. 5 here Job's plots and Reversibility studies To explore the stoichiometry of CHB binding with Zn2+, Job's plot was performed in PBS (pH = 7.24, 60 % DMF) to obtain the binding stoichiometry. From Figure. 6 & Figure. S8, we could search for the value of [probe CHB]/[ probe CHB + Zn2+] was 0.63, which indicated that a 1:2 complex was formed between CHB and Zn2+. Benesi-Hildebrand equation was used to calculate the binding constant (Ka) of CHB and Zn2+, based on the fluorescence titration data with a good relationship (R=0.998)[45, 46]. Constructed the diagram of 1/(F-F0) against 1/[Zn2+] (Figure. S6), the binding constant (Ka) of CHB with Zn2+ in PBS (pH = 7.24, 60 % DMF) solution was found to be 1.32×104 M-2. According to the formula ((LOD) = 3(SD)/S), the limit of detection was calculated as 9.46 × 10-6 M, which was lower than many reported Zn2+ probes (Table 1)[54-60]. In addition, the fluorescence intensity increased linearly with the concentration of Zn2+ in the range of 0 to 30 μM (Figure. S7), which revealed that CHB is effective for the quantitative detection of Zn2+ in PBS (pH = 7.24, 60% DMF). Figure. 6 here Effects of response time, and EDTA on Zn2+ detection Quick response time was conducive to improving practical apply of fluorescent probes. So we examined the change of CHB (0.1 μM) upon addition different concentration of Zn2+ (5.0 μM, 10 μM, 15 μM) over time in PBS (pH = 7.24, 60% DMF) by fluorescence spectra. As showed in Figure. 7, CHB reached the fluorescent saturation point at 25 s, so CHB could rapidly react with Zn2+ and be widely applied to measure Zn2+. To further consider the reversibility of CHB with Zn2+, chelate EDTA was introduced into the system to bind with Zn2+ in PBS (pH = 7.24, 60% DMF)[47]. The reversible data of same concentration EDTA and Zn2+ measured in PBS (pH = 7.24, 60% DMF) containing 0.1 μM CHB were shown in Figure. 8 & Figure. S9, and it can be seen that CHB possess an excellent reversibility. Figure. 7 here

Figure. 8 here Mechanism of binding between Probe CHB and Zn2+ The mass spectrometry is widely used to analyze the product in solution. As showed in Figure. 9, a peak at m/z = 264.7752, corresponding to [2 CHB + Zn + H + Na + 2H2O] 2+ was clearly obtained, which indicated that a 1:2 stoichiometry complex was formed between Zn2+ and Probe CHB. This result is in good accordance with the results of Job's plot. Besides, we make use of the density functional theory (DFT) to further understand the formation of the CHB-Zn2+ complex[48-51]. Geometries of CHB and Zn2+ were optimized by the Gaussian 09 program with the 6-31G(d) basis set at the level of B3LYP. As shown in Figure. 10, both of the HOMO and LUMO of CHB are delocalized π orbitals. The large HOMO-LUMO gap (4.425 eV) shows the high stability of the CHB. The complexity of CHB-Zn2+ was formed by the chelation of Zn with the nitrogen and oxygen of Probe CHB. The bond lengths of Zn-N and Zn-O in the complex Probe CHB-Zn2+ were 1.916 Å and 2.040 Å, respectively. Therefore, the N binding with Zn is much stronger than Zn-O. In Probe CHB-Zn2+, except for the LUMO of CHB, the dxy orbital of Zn also contributes to its LUMO that is also a typical π orbital. However, the HOMO of CHB-Zn2+ complex is the π*-orbital that is consisting of the Pz orbitals of N and dyz orbital of Zn. The HOMO-LUMO energy gap decreased from Probe CHB (4.425 eV) to the complex of CHB-Zn2+ (2.818 eV), indicating that CHB-Zn2+ is more likely to be induced, result in the visual fluorescence enhancement under Uv lamp. Figure. 9 here. Figure.10 here. Cell imaging study Based on the specific fluorescence response of CHB to Zn2+, the sensing performance of HEK293T to Zn2+ in living cells by confocal fluorescence microscopy was studied[52-53]. The MTT assay results showed that there was remaining 81% cell viability even the CHB was 80 μM(Figure. S10). From Figure.11, the HEK293T cells were incubated with 10 μM Probe CHB showed no fluorescence image. While after being incubated of HEK293T cells with same CHB-Zn2+ complex (40 μM), the bright green fluorescence was generated when the cells

were imaged by fluorescent microscope. The result indicated that CHB has potential applicability for detecting Zn2+ in living cells with well cell-permeable. Figure.11 here. Comparison with other probes Compared with the recently reported chemosensors, the detection limit of CHB is 9.46 μM. As summarized in Table 1, most of them are Schiff base molecules and it possesses a lower detection limit which bears more lone N in cheating site. Our method had comparable sensitivity, higher binding constant, outstanding reversibility and a fast reaction time (nearly 30 s) in PBS (pH = 7.24, 60 % DMF) compared with other reported probes above. We can devote our energy to search the targetability to organelle such as mitochondria and lysosomes, to meet the deep requirements of potential applications in biology. Table 1 here Conclusions In summary, the preparation process and photophysical characterization of a coumarin derivative Probe CHB (2-oxo-2H-chromene-3-carbohydrazide) are presented in this communication. Probe CHB exhibited highly sensitive and selective binding with Zn2+ over other anions and metal ions. After treated with zinc ions, the fluorescence of Probe CHB at 505 nm was enhanced due to a 2:1 complex was formed between Probe CHB and the Zn2+ at room temperature. The detection limit of Zn2+ was 9.46×10-6 M in PBS (pH = 7.24, 60% DMF). It showed excellent reversibility towards Zn2+ and other cheating agent EDTA. The utilization of Probe CHB for the determination of Zn2+ in living cells was evaluated, and the results revealed that it had potential applications for biological imaging. Acknowledgements This work is financially supported by the practice innovation training program projects for the Jiangsu College students (201810304069Y) and sponsored by Qing Lan Project of Jiangsu Province. Reference

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Captions for tables

Table 1 The comparison of Probe CHB with other reported probes in the literature

Table 1 The comparison of Probe CHB with other reported probes in the literature

Association Compound

LOD / M

Application

Ref.

-

4.6×10-5

Urine sample

[54]

5.18×105

3.66×10-8

Constant / M-1

Living plants [55] cells imaging

6.72×105

2.29×10-9

Living

cells [56]

imaging -

1×10-8

Living

cells [57]

imaging 4.04×104

2.58×10-7

Living cells [58] imaging

1.19×103

7.8×10-5

Living

cells [59]

imaging 5.82×104

1.34×10-7

Test strips [60] experiments

1.22×106

9.46×10-6

Living

cells

imaging

This work

Captions of Scheme and Figures Scheme 1 Synthesis of Probe CHB Scheme 2 Fluorescence response mechanism of CHB towards Zn2+ by PET Figure.

1

Fluorescence

spectra

(excited

at

430

nm)

of

CHB

(5.0

μM)

in

PBS (pH = 7.24, 60% DMF) in the presence of 10 equiv. of various metal ions. Slit: excitation/emission=5.0nm/5.0nm. Figure. 2 Fluorescence Emission spectrum of CHB (5.0 μM) in PBS (pH = 7.24, 60% DMF) upon incremental addition of Zn2+. Inset: the visible fluorescence changes upon UV irradiation. Figure. 3 Histogram of F505 nm of CHB in the presence of different metal ions: A-probe CHB, B-Na+, C-K+, D-Mg2+, E-Ca2+, F-Ba2+, G-Cr3+, H-Co3+, I-Mn2+, J-Fe3+, K-Ni2+, L-Cu2+, M-Cd2+, N-Al3+, O-Pb2+, P-Bi3+, Q-Ag+, R-Sn2+, S-Sr2+, T-NH4+, U-Fe2+, V- Zn2+. Figure.

4

Fluorescence

spectra

(excited

at

430

nm)

of

CHB

(5.0

μM)

in

PBS (pH = 7.24, 60% DMF) in the presence of 10 equiv of various anions. Slit: excitation/ emission =5.0nm /5.0nm. Figure. 5 Histogram of F505 nm of CHB in the presence of different metal ions: a-probe CHB, b-Cl-, c-Br-, d-I-, e-SO42-, f-PO43-, g-H2PO4- , h-OH-, i-HCO3-, j-NO3-, k-Br-, l-C2O42-, m-F-, n-HPO42-, o-S2O32-, p-NO2-, q-Ac-, r-P2O74-, s-B4O72-, t-D-3-HB, u-HSO3- , v-SO32-, w-S2-, xZn2+ (λex = 430 nm) Figure. 6 Job's plot for determining the stoichiometry of CHB and Zn2+ Figure. 7 Time-dependent fluorescence intensity of CHB and after addition various amount of Zn2+ Figure. 8 Reversibility experiment of CHB (0.10 μM) in PBS (pH = 7.24, 60% DMF) with EDTA and Zn2+ Figure. 9 ESI mass spectra of CHB upon addition of excess Zn2+. Figure.10 Optimized structures and molecular orbitals (LUMO and HOMO) of CHB and Zn2+. Figure.11 a) bright field of HEK293T cells with C1; b) dark field image of HEK293T cells incubated with CHB; c) bright field of HEK293T cells with CHB and Zn2+ using 405 nm laser excitation and collection of fluorescence signals from 430 to 490 nm; d) dark field image of HEK293T cells with CHB and Zn2+.

Scheme 1 CHO H

HN

O

O

O

O O

O

O CH3CH2OH

O

O

O

O

O

O

OH O O

O O

O O

O

O O

O

O O

OH O

O

-H2O

O

OH

O

Hydrazine hydrate CH3CH2OH

O

O

N H

NH2

(CHB)

Scheme 1 Synthesis of Probe CHB

Scheme 2

Scheme 2 Fluorescence response mechanism of CHB towards Zn2+ by PET

Figure.1

Figure. 1 Fluorescence spectra (excited at 430 nm) of CHB (5.0 μM) in PBS (pH = 7.24, 60% DMF) in the presence of 10 equiv of various metal ions. Slit: excitation/emission=5.0nm/5.0nm.

Figure.2

Figure. 2 Fluorescence Emission spectrum of CHB (5.0 μM) in PBS (pH = 7.24, 60% DMF) upon incremental addition of Zn2+(0-20 µM). Inset: the visible fluorescence changes upon UV irradiation.

Figure.3

Figure. 3 Histogram of F505 nm of CHB in the presence of different metal ions: A-probe CHB, B-Na+, C-K+, D-Mg2+, E-Ca2+, F-Ba2+, G-Cr3+, H-Co3+, I-Mn2+, J-Fe3+, K-Ni2+, L-Cu2+, M-Cd2+, N-Al3+, O-Pb2+, P-Bi3+, Q-Ag+, R-Sn2+, S-Sr2+, T-NH4+, U-Fe2+, V-Ba2+, W- Zn2+.

Figure.4

Figure. 4 Fluorescence spectra (excited at 430 nm) of CHB (5.0 μM) in PBS (pH = 7.24, 60% DMF) in the presence of 10 equiv of various anions. Slit: excitation/ emission =5.0nm /5.0nm.

Figure.5

Figure. 5 Histogram of F505 nm of CHB in the presence of different metal ions: a-probe CHB, b-Cl-, c-Br-, d-I-, e-SO42-, f-PO43-, g-H2PO4- , h-OH-, i-HCO3-, j-NO3-, k-Br-, l-C2O42-, m-F-, n-HPO42-, o-S2O32-, p-NO2-, q-Ac-, r-P2O74-, s-B4O72-, t-D-3-HB, u-HSO3- , v-SO32-, w-S2-, x- Zn2+ (λex = 430 nm)

Figure.6

Figure. 6 Job's plot for determining the stoichiometry of CHB and Zn2+

Figure.7

Figure. 7 Time-dependent fluorescence intensity of CHB and after addition various amount of Zn2+

Figure.8

Figure. 8 Reversibility experiment of CHB (5.0 μM) in PBS (pH = 7.24, 60% DMF) with EDTA and Zn2+

Figure.9

Figure. 9 ESI mass spectra of CHB upon addition of excess Zn2+.

Figure.10

Figure.10 Optimized structures and molecular orbitals (LUMO and HOMO) of CHB and Zn2+.

Figure.11

Figure.11 a) bright field of HEK293T cells with C1; b) dark field image of HEK293T cells incubated with CHB; c) bright field of HEK293T cells with CHB and Zn2+ using 405 nm laser excitation and collection of fluorescence signals from 430 to 490 nm; d) dark field image of HEK293T cells with CHB and Zn2+.

A Coumarin-based turn-on chemosensor for selective detection of Zn(II) and application in live cell imaging Shang Yanfang*, [a] [a]

Wang Hualai[a]

Bai Hui*, [b]

School of Chemistry and Chemical Engineering, Nantong University, Nantong, 226019, [email protected]

[b]

Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024; [email protected]

Highlights 1. CHB based on coumarin was designed and synthesized. 2. CHB displays a grateful turn on property for Zn2+ with fast response time (20 s) 3. The low detection limits was 0.95 μM and the binding constant was 1.22 × 106 M-1. 4. CHB was successfully applied to monitor Zn2+ and the mechanism was verified by HR-MS and DFT.

Declaration of Interest Statement The authors declared that they have no conflicts of interest to this work.