A porous and luminescent metal-organic framework containing triazine group for sensing and imaging of Zn2+

Accepted Manuscript A porous and luminescent metal-organic framework containing triazine group for 2+ sensing and imaging of Zn Tianen Fan, Tifeng Xia, Qi Zhang, Yuanjing Cui, Yu Yang, Guodong Qian PII:

S1387-1811(18)30115-X

DOI:

10.1016/j.micromeso.2018.02.050

Reference:

MICMAT 8813

To appear in:

Microporous and Mesoporous Materials

Received Date: 10 November 2017 Revised Date:

8 February 2018

Accepted Date: 27 February 2018

Please cite this article as: T. Fan, T. Xia, Q. Zhang, Y. Cui, Y. Yang, G. Qian, A porous and luminescent 2+ metal-organic framework containing triazine group for sensing and imaging of Zn , Microporous and Mesoporous Materials (2018), doi: 10.1016/j.micromeso.2018.02.050. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. 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.

ACCEPTED MANUSCRIPT

Graphical abstract A porous and luminescent metal-organic framework

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containing triazine group for sensing and imaging of Zn2+ Tianen Fan, Tifeng Xia, Qi Zhang, Yuanjing Cui*, Yu Yang, Guodong Qian*

A porous and luminescent lanthanide metal-organic framework, TbTATB, for

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sensing and imaging of Zn2+ was successfully synthesized. TbTATB exhibits

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selective and sensitive detection of Zn2+ even in the present of other relevant metal ions with the detection limit of 10.5 nM. Furthermore, TbTATB could

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perform as the marker of Zn2+ with the coexist of living cells.

ACCEPTED MANUSCRIPT

A porous and luminescent metal-organic framework containing triazine group for sensing and imaging of Zn2+ Tianen Fan, Tifeng Xia, Qi Zhang, Yuanjing Cui*, Yu Yang, Guodong Qian*

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State Key Laboratory of Silicon Materials, Cyrus Tang Center for Sensor Materials and Applications, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, P. R. China. E-mail: [email protected], [email protected]

Abstract: The rapid development of functionalization of lanthanide metal organic frameworks (Ln-MOFs) offers the potential for biomarkers sensing. It is closely associated with biology science and clinic medicine. In this work, a porous and luminescent terbium metal-organic

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framework TbTATB has been designed and solvothermally synthesized. The PXRD results demonstrated the commendable stability of this sensor. Enhanced luminescence of TbTATB origin from Tb3+ was observed in the presence of Zn2+, which is a kind of biologically importmant ion. This turn-on pattern was ultilized for sensing Zn2+. TbTATB exhibited excellent sensitivity and slectivity towards Zn2+ in aqueous solution with

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the detection limit of 10.5 nM. What’s more, it has fairly acceptable biocompatibility which was fully verified by cytotoxicity test. In the state of coexistence with living cells, visible increased green light of TbTATB emerged after the addition of Zn2+, while the survival state of cells was hardly disturbed. Markedly, this is the first time that a luminescent Tb-MOF can act as a sensor for sensing and imaging of Zn2+ ions simultaneously. What’s more, the results also guide a new application direction of MOFs and supply a new way for the detection of other analytes in biological systems.

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Key words: metal-organic frameworks, turn-on, luminescent, sensing, imaging

1. Introduction 2+

numerous

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Zinc (Zn ) is recognized to play pivotal roles in fundamental

biological

processes

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covering enzyme regulation, gene expression, nerve transmission and cell apoptosis in living systems [1]. Owing

to

the

unique

10

3d 4s

0

electronic

luminescent signals, stabilized and time-dependent luminescence signals could be obtained. It has been developed

in

detection fields

and

possesses

superiorities such as conveniences, good sensitivity, excellent selectivity, rapid response and noninvasive 2+

sensing [3]. Generally, a luminescent Zn 2+

contains two essential parts: Zn

sensor

chelating or

2+

configuration, Zn exists in the +2-oxidation state in the living systems and shows no spectroscopic or magnetic

signals

[2].

Recently,

luminescence

techniques have increased our insight into more possibilities to look into this biologically important

binding moieties and luminescent centers capable of emitting light [4]. To date, several organic fluorophores sensors have been developed for Zn

2+

detection, such as quinolone and coumarin [5-8]. However, there are some imperfections including

ion. Based on monitoring the change of the

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ACCEPTED MANUSCRIPT intricate synthetic route, weak luminescence, short

turn-off sensors, as they can effectively avoid false

luminescent lifetime and poor biocompatibility,

response and obtain a better signal-to-noise ratio.

leading to strong desire of developing new sensors

The quenching effect might be caused by a series of

to overcome these problems [9].

environment and instrument factors which brings difficulties to analyze the actual contributor [28-29].

novel crystallographic porous materials which can

Therefore, there is thereby an urgent need but it is

be synthesized by simply self-assembly process with

still a significant challenge to seek functional Ln-

corresponding metal cations or clusters and organic

MOFs

ligands [10-11]. They have attracted more and more

biocompatibility to achieve the purpose of highly

attention due to the peculiarities including simple

selective and sensitive sensing and imaging of Zn

synthetic method, modifiable pore size, designable

in biological systems.

and

unique

luminescent

good

water-stability

and

2+

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sites

with

Considering the unique luminescent properties of

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functionalized

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In the past few decades, MOFs are emerging as

properties [12-15]. Particularly, lanthanide MOFs

terbium and the fact that terbium is preferential to

(Ln-MOFs) can exhibit intense, long-lived emission

coordinate

in the visible region, which are applicable for

incorporation of carboxyl groups into the ligand

luminescent sensing and imaging [16-22].

should be a feasible approach. In addition, Zn

with

the

oxygen

atoms,

the

2+

has

Up to now, several luminescent MOFs sensors for

strong coordination ability with nitrogen atoms, a

2+

ligand

have been reported [23-24]. However, most of

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Zn

containing

2+

Consequently, a trigonal-planar organic ligand

from inferior stability and poor biocompatibility,

4,4',4''-striazine-2,4,6-triyl-tribenzoic acid (H3TATB)

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mechanism. In addition, MOFs are usually suffering

imaging in biological systems

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2+

Zn

supply

functionalized

application for Zn

for

might

them are based on the luminescence quench

which restrict the detection conditions and the

sites

triazine

sensing

[30].

was chosen as the ligand to construct a luminescent MOF with terbium. As expected, within the 3+

[25]. As is well-known, Imaging of analytes in

synthesized framework TbTATB, all the Tb ions are

biological environments is a critical strategy for the

coordinated by oxygen atoms, leaving abundant

discovery and treatment of disease. And with the

exposed

development

selectivity

of

microscopic

techniques,

Lewis and

basic

sites.

sensitivity

Meanwhile,

were

studied

the by

luminescent sensors supply new aspects that we

luminescence

could see the direct-viewing distribution of analytes

Furthermore, the biocompatibility of TbTATB was

in

Moreover,

evaluated by MTT test. And subsequent imaging

luminescent turn-on sensors are preferable than

experiments with living cells were also conducted.

biological

systems

[26-27].

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spectra

in

aqueous

solutions.

ACCEPTED MANUSCRIPT As anticipated, the as-developed Ln-MOF TbTATB is

Fourier maps in the refinement cycles. The scattering

demonstrated to have favorable accuracy and

from the highly-disordered lattice guest molecules were

2+

repeatability for Zn sensing. Moreover, it might be potentially applied for imaging of Zn

2+

in biological

systems.

removed using the SQUEEZE procedure implemented in the PLATON package. Selected crystal parameters, data collection, and refinement are summarized in Table S1. 1582634

contains

the

supplementary

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CCDC

2. Experimental

crystallographic data for this paper. Elemental analyses were performed on a Thermo Finnigan Flash EA 1112

2.1 Materials and characterization

element analyzer. Powder X-ray diffraction (PXRD) data

reagents were purchased from commercial sources and used without further purification. Bruker SMART APEX-II

detector

was

employed

to

diffractometer (Japan) using Cu-Kα (λ= 1.542 Å) beam o

with the recording rate 5 /min with the 2θ ranging from

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single crystal diffractometer (Germany) with a CCD

were collected on a PANalytical X'Pert Pro X-ray

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All the initial chemicals, including solvents and

implement

the

crystallographic measurements for TbTATB, using

graphite-monochromatic Mo Kα radiation (λ= 0.71073 Å) at 296 K. CrysAlisPro was used to conduct the

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determination of the unit cell and data collection. The

data reduction was carried out with Bruker SAINT. The

data sets were corrected by empirical absorption

correction using spherical harmonics, implemented in

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the SCALE3 ABSPACK scaling algorithm. The cell parameters determination and date collection was

3 to 40 degrees at 293 K. Thermogravimetric analyses (TGA) were carried out on a Netzsch TG209F3(Germany) -1

with a heating rate of 10 K min under N2 atmosphere. X-ray photoelectron spectroscopy (XPS) studies were carried out on an AXIS SUPRA instrument with an Al Kα monochromated (150 W) and delay line detector. The samples were charge-neutralized using a coaxial fully automatic single electron source charge neutralizer and tested under the identical condition. Spectra were analysed using ESCApe software. The C1s signal at 285 eV was used to calibrate the binding energy scale.

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performed directly by CrysAlisPro program. The crystal structure was determined by direct methods and refined by the full-matrix least-squares method with the SHELX-2014 program package. All non-hydrogen atoms were located successfully from Fourier maps and were refined anisotropically. The H atoms on the ligands were placed in idealized positions and refined using a riding model. The disordered lattice DMA, EtOH, and H2O

2.2 Synthesis of TbTATB

A mixture of Tb(NO3)3∙6H2O (70mg, 0.15mmol), 4,4'4''-striazine-2,4,6-triyl-tribenzoic acid (H3TATB) (30mg, 0.068mmol), DMA (10mL), EtOH (3.5mL), H2O (1.0mL) and CH3COOH (100μL) were sealed into a 20mL glass vial and ultrasonically dissolved to from clarified o

solution. Then the vial was heated at 105 C for 24

molecules could not be located successfully from

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ACCEPTED MANUSCRIPT hours, then cooled to room temperature, yielding

were observed upon excitation at 356 nm. The emission

colourless rhombus crystals. Yield: 75.4%. The crystals

and excitation spectra for the samples were recorded in

were collected by filtration and washed with DMA and

suspension state. Suspension could almost remain

EtOH for several times, respectively. Then the crystals

homogeneous within the test time. Triplicate operations

o

for all samples were performed to maintain more

were reserved for PXRD test and other experiments.

accurate results.

2.3 N2 sorption experiments

2.5 Biocompatibility test

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were drying in a 60 C oven overnight, the dried samples

2.5.1 Cell Culture: The rat pheochromocytoma (PC12)

TbTATB, the N2 sorption experiment was carried out

cells were incubated in Dulbecco’s Modified Eagle’s

with the Micromeritics ASAP 2020 surface area analyzer.

Medium (DMEM, Neurons) with 10% fatal bovine serum

Before the N2 sorption measurements, the fresh sample

(FBS) and 1% penicillin/streptomycin (P/S, Boster) for 2

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In order to evaluate the permanent porosity of

of TbTATB was guest-exchanged with dry methyl

days in a humidified incubator (37 °C, 5% CO2). 2.5.2 MTT Test: The biocompatibility of TbTATB was

was freshly exchanged every four hours. Then, the

evaluated by using standard MTT assay in a 96-well

volatile methyl alcohol was removed under vacuum at

plate to assess the viability of cultured cells. Firstly, cells

100 °C. Then filtered and degassed at 298 K for 12 hours

were incubation in the humidified incubator for 24h,

and 348 K for 12 hours under high vacuum to obtain the

and then TbTATB were added to the wells with different

activated TbTATBa.

concentrations (5, 20, 50, 80 and 100 μg/mL) and

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2.4 Luminescence study

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alcohol for two days. During this period, methyl alcohol

The emission and excitation spectra and luminescent lifetime for the samples were recorded on an Edinburgh FLSP900

luminescence

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Instrument

spectrometer

(England), Xe lamp and μF Flashlamp are severally used as the light source. The samples of TbTATB were grinded before experiment, then 1 mg TbTATB was weighed and added to several cuvettes containing 1 mL 2+

different concentrations of Zn

solutions prepared in

deionized water, respectively. Same operations were

incubated with the PC12 cells for another 4h in the incubator. After that, 50 μL of 1× MTT solutions were added to each tested well and incubated for 4h. Subsequently, all media were removed, and 150 μL of dimethyl sulfoxide (DMSO) was added to each well. Finally, the absorbance of each sample at 490 nm was measured using a microplate reader. The cell viability was calculated as the ratio of the absorbance of the sample well to that of the cell control and expressed as a percentage. All experiments were sextuplicated, and the results were averaged.

conducted for different metal ions. After dispersed ultrasonically for one minute, the florescence properties

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ACCEPTED MANUSCRIPT 2.6 Optical imaging experiments

Optical imaging of PC12 cells was taken on by an optical microscope at room temperature. Bright field and luminescent field with excitation wavelengths of 4

365 nm were taken. The cells (10 cells/mL) were

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seeded in a 24-well plate at the bottom of each well for 2+

24h incubation. Then 10 M Zn and 50 μg/mL TbTATB were added to the wells and incubated for another 4h,

out using an optical microscope with a 20× objective at room temperature. Both luminescent and bright-field

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images of PC12 cells were recorded.

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respectively. Luminescence imaging of cells was carried

3. Results and discussion

3.1 Preparation and characterization of TbTATB

The luminescent sensor was acquired by reacting

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Tb(NO3)3∙6H2O with H3TATB in a mixed solvent of N,N-

dimethyl acetamide (DMA), ethyl alcohol (EtOH),

deionized water (H2O) and acetic acid (CH3COOH) at a o

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105 C oven for 24 hours. The crystal structure of TbTATB is shown in Figure 1b. Single-crystal X-ray

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diffraction (SCXRD), elemental analysis (EA) and thermo gravimetric analyses (TGA) were employed to identify

Figure 1 a) Coordination mode of TATB

3-

ligands. b)

3+

Coordination mode of Tb . c) Crystal structure of TbTATB viewed along the b axis. (Tb green, C gray, O red, N blue; all H atoms are omitted for clarity) and d) PXRD patterns of synthesized TbTATB and TbTATB immersed in H2O for 8 hours.

the formula [Tb(TATB)(DMA)(H2O)]·(DMA)3. Elemental analysis calcd (%) for TbTATB： C 49.85，H 5.23，N

ligand, one coordinated DMA molecule and one H2O

10.17 ； Found: C 48.54 ， H 5.19 ， N 9.97. SCXRD

molecule. All the Tb

analysis displayed that TbTATB crystallizes in the

eight oxygen atoms, in which six are from H3TATB

monoclinic space group C2/c (Figure 1 and Table S1). The

unit

cell

of

TbTATB

consists

of

crystallographically unique Tb (III) ions, one TATB

3-

one

3+

ions are eight-coordinated by

ligands and the other two from the coordinated DMA molecules and H2O molecules, respectively. The three carboxylate groups in ligand show two different

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ACCEPTED MANUSCRIPT coordination modes: syn–syn bridging bidentate and

PXRD patterns in Figure 1c exhibit that the structure of

chelating-bridging tridentate, as shown in Figure 1a. The

TbTATB

3+

unchanged

after

immersed

in

ions coordinated with carboxylate

deionized water for 8 hours. Therefore, the relatively

groups to form the secondary building unit (SBU)

good stability of TbTATB endows it with the possibility

Tb2(COO)6. Then the SBUs are packed together to form

to be a commendable sensor material in aqueous

3D framework structures with unique pores through the

solutions.

ligands, as shown in Figure 1c. The phase purity and 3.3 Detection of Zn water-stability of synthesized TbTATB were further

2+

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two adjacent Tb

remains

The dried TbTATB crystals were firstly grinded into

in Figure 1d. The porous property of TbTATB was

fine and uniform powder to guarantee homogeneous

revealed by N2 sorption studies (BET surface area:

dispersion in water. Then the obtained powder was

2

−1

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confirmed by powder X-ray diffraction (PXRD), as shown

simply immersed in an aqueous solution with different

429.86 m g , Figure S8).

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2+

Zn concentration to form suspension for luminescence

3.2 Luminescent properties

studies.

The luminescent properties of solid H3TATB and

It

is

worthwhile

mentioned

that

the

luminescence emission intensity of TbTATB was 2+

gradually enhanced with the Zn

be seen from Figure S2, under UV light excitation, the

increasing from 0 to 10 μM (Figure 2a). Specially, the D4

free H3TATB ligand molecules can absorb photons with

→ F5 transition of Tb present visible green light at 544

appropriate energy, the luminescence emission at about

nm with the highest intensities. The increasing effect

430 nm is resulted from π → π* transition, namely

can be fitted by the following equation, I/I0= 1 +

radiative transition from the first singlet state to the

KSV[Zn ], where I0 and I are independently the

ground

singlet

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TbTATB were measured at room temperature. As can

state.

TbTATB

5

showed

7

strong 3+

characteristic transitions ( D4 → FJ, J = 6−3) of Tb

7

concentration 5

3+

2+

luminescence intensity of the suspension at 544 nm in 2+

the absence and presence of Zn , KSV represents the

494, 544, 587, and 622 nm, without the emission of

increasing constant, and [Zn ] is the Zn concentration

H3TATB. The luminescent phenomenon of TbTATB

of the suspension. As can be seen from Figure 2b, there

suggests that the ligand-to-metal energy transfer

is an excellent linearity between I/I0 and [Zn ] at a

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at

3+

(LMET) from H3TATB molecules to Tb

centers occur

2+

2+

2+

specific concentration range, which is indicative of the 2+

effectively [31]. Interestingly, identical characteristic

sensitive sensing properties of TbTATB towards Zn

emission bands were obtained in the suspension of

aqueous solutions.

TbTATB (Figure S4) in deionized water (1mg/mL) compared with solid state (Figure S3). Moreover, the

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in

ACCEPTED MANUSCRIPT Consequently, the LOD of TbTATB sensor was evaluated through the equations below,

/ (1)

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∑

(2)

where Sb is the standard deviation of the multiple

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detection signals of the blank solutions (N = 20), S is the slope of the fitting line in Figure S4, F0 is the

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luminescence emission intensity of TbTATB in deionized 2+

water without Zn and F is the mean of F0. On the basis

Figure 2 a) The luminescent emission spectra (excited at

of the above method, the LOD was assessed to be 10.5

356 nm) of TbTATB in solutions (1mg/mL) with different

nM, which is even lower than the minimum standard

2+

Zn

concentrations and b) Stern-Volmer plots of I/I0 2+

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versus Zn concentration and the fitting line in aqueous solution.

To further judge the sensitivity of the luminescent

2+

level of Zn in serum.

Interference from other metal ions should be taken

into

account

when

considering

physiological

applications. In order to confirm the sensing selectivity of TbTATB to Zn

2+

among other ions, TbTATB was

immersed in the aqueous solutions (1mg/mL) containing

calculated. LOD reflects the minimum concentration of

several different kinds of metal ions including Al , Mn ,

the analyte to be measured in a sample by a certain

Ni , Mg , Co , Na , Ca , Cr , Pb

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sensor TbTATB, the detection limit (LOD) of TbTATB was

3+

2+

2+

2+

+

2+

3+

2+

and Cd

2+

2+

to get

analytical method in a given degree of reliability. In

suspensions (10 μM) for luminescence studies under

accordance

identical conditions. The luminescence properties are

with

the

requirements

set

by

the

international federation of pure and applied chemistry

recorded and compared.

(IUPAC), the general value of signal-to-noise ratio for

As shown in Figure 3a, the luminescent intensity of

spectrochemical analysis is recommended as 3. As can

TbTATB incorporated with the metal ion is tightly

be seen in Figure S5, variation in luminescent intensity is

concerned with the varieties of the metal ions. Only the

linearly

dependent

on

2+

Zn

amount

at

low

2+

addition of Zn

caused a significant increase of

concentrations from 0 to 1 μM.

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ACCEPTED MANUSCRIPT 2+

luminescent intensity, whereas other metal ions have a

TbTATB is a highly sensitive Zn

neglected impact on the luminescence intensity.

doesn’t suffer from the interference of other metal ions.

sensing material and

The conceivable mechanism for the turn-on and selective sensing of Zn

2+

will be summarized below. 3+

Generally, the luminescence intensity of Tb

is closely

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associated with the LMET efficiency [32-33]. Owning to the strong coordination abilities with N, the electron2+

deficient Zn

is supposedly available for interactions

with abundant Lewis basic pyridyl sites in the ligands

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[34]. The specific interactions can not only make the 3+

energy transfer process from H3TATB to Tb

more

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effective, leading to enhanced luminescence intensity, but also distinguish Zn

2+

from other metal ions,

exhibiting high selectivity [35-37]. Besides, the unique pore structure is beneficial for the interaction between 2+

Zn

and N atoms in ligands. In accordance with the

results of luminescence spectra, the luminescent

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Figure 3 a) The luminescence intensity histograms of TbTATB dispersed in deionized water with the addition of different metal ions (10 μM) and b) subsequent 2+

addition of Zn ion (red, 10 μM). Emission intensities at 5

7

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the D4 → F5 transition were selected.

lifetime of TbTATB increased from 488 μs to 500 μs in 2+

the absence and presence of 10 μM Zn , as shown in Figure S6 and Table S2. 2+

To further confirm the bond mode between Zn and nitrogen atoms, X-ray photoelectron spectroscopy (XPS) studies were conducted. As shown in Figure 4, The N1s

2+

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In detail, except for the slight increase for Cd , the others show a luminescence intensity decrease. To 2+

deeply evaluate the selectivity of TbTATB to Zn , the luminescence spectra were measured in the coexistence 2+

of Zn and other ions. As can be seen from Figure 3b, there is little change in increasing efficiency with the coexistence of other metal ions as compared with that 2+

in the presence of single Zn . The results indicated that

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ACCEPTED MANUSCRIPT Figure 4 XPS spectra of the original TbTATB (black) and 2+

nature to culture plate and the unique morphology with

Zn -incorporated TbTATB (red) immersed in 10 mM

enriched neurites that reflects their living state, which

deionized H2O solution of Zn(NO3)2.

are beneficial to the observation by microscopy [39]. The cell viability was characterized by the amount of mitochondrial in viable cells. Owing to the ability to the

MTT

into

formazan,

mitochondria

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reduce

metabolism of the cells could be reflected by the decline of MTT to formazan [40-41]. Therefore, the MTT assay was conducted by incubating PC12 cells with TbTATB at

Figure 5 Simplified schematic of ligand-metal energy

The dose response of TbTATB on PC12 cells exhibits decreased MTT reduction to formazan with the growing

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transfer (LMET) process for luminescence emission and

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different does (5, 20, 50, 80 and 100 μg/mL) for 24 h.

concentration of TbTATB. As shown in Figure 6, there is

2+

influence of Zn on LMET.

a slight decrease of the cell viability with the increase of

peak of nitrogen atoms from pyridyl at 399 eV in 2+

TbTATB is shifted to 398.5 eV on the addition of Zn ,

demonstrating a weak binding of nitrogen atoms with 2+

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2+

Zn in Zn -incorporated TbTATB [38]. A peak at 407.2 2+

eV in the N1s XPS spectra for Zn -incorporated TbTATB 3-

is attributed to NO counterions. The observed changes

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in the XPS spectral profile of TbTATB supported the 2+

participation of nitrogen in the complexation with Zn ,

maintains at about 100% after incubating with TbTATB

sensor at 50 μg/mL. It is indicative that the introduction of low-concentration MOFs can barely influence the viability of PC12 cells. For more visualized results, the optical microscopy imaging was also used to monitor the living state of cells and luminescence properties of TbTATB both in the

bright filed and luminescent field with 365nm UV light

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which affects the energy transfer process from H3TATB

the TbTATB concentration, while the viability of cells

3+

to Tb , resulting in the improvement of LMET efficiency, as shown in Figure 5.

3.5 Imaging of Zn

To

further

2+

evaluate

the

biocompatibility

and

biological application of TbTATB, MTT assay and optical microscopy imaging under cell atmosphere were employed. PC12 cells was chosen for the adhesion

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ACCEPTED MANUSCRIPT Figure 6 Cell viability data of MOFs obtained from

cells show desirable appearance of neurites emitting

cultured cells with the untreated cell as a control. Error

compared with the control cells. What’s more, TbTATB

bars represent the standard deviation of uncertainty for

perform visible green light under 365 nm UV light

each point.

excited at the cell atmosphere (Figure 7c). Many MOFs clusters are observed as green dots and accumulated

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around the cells. The co-localized luminescence signals indicated that there were no appreciable changes on the state, morphology, and long stretching microtubular of PC12

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cells after the introduction of TbTATB, demonstrating the good biocompatibility of TbTATB even at a relatively 2+

give

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high concentration. Subsequent addition of Zn

rise to a brightness enhancement without affecting the

living state of PC12 cells (Figure 7d). The turn on effect

Figure 7 Optical microscopy images of PC12 cells a) without treatment, b) incubated with 10

-3

2+

M Zn , c)

-3

2+

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incubated with 50 mg/mL TbTATB and d) subsequent

addition of 10 M Zn . Optical bright field microscopy image for a1, b1, c1 and d1, optical luminescent field

microscopy image illuminated with 365nm light for a3,

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b3, c3 and d3, overlapped for a2, b2, c2 and d2.

in the cell environments agrees well with the phenomenon that was discovered in the luminescence

study. The results indicate that TbTATB is biocompatible

among neuron survival and neurite outgrowth owing and neurite outgrowth owing to the enriched neurites. Meanwhile,

exhibited

TbTATB

coincident

luminescence properties with the spectra study. On account

of

good

biocompatibility

and

unique

luminescence properties, TbTATB could be an excellent

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excited. As shown in Figure 7, the PC12 cells attach candidate for turn-on luminescent sensing and imaging

closely to the substrate and show abundant growth of

2+

of Zn .

axons and dendrites in the absence of both TbTATB and 2+

Zn

(Figure 7a). There is slight influence on both

4. Conclusions

morphology and amount on PC12 cells on addition of 2+

Zn

with the concentration of 10

-3

M (Figure 7b).

Afterwards, on the basis of the MTT results, 50 μg/mL

In conclusion, we have successfully designed and synthesized a luminescent terbium metal-organic 2+

was

chosen

as

the

concentration

for

imaging

framework TbTATB for Zn

sensing and imaging. 2+

experiment. In the case of 50 μg/mL TbTATB, the PC12

TbTATB exhibited not only high selectivity for Zn over

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ACCEPTED MANUSCRIPT other

competitive

metal

ions

with

increasing

[5]

P. Hu, R.Wang, L. Zhou, L. Chen, Q. Wu, M. Han,

luminescent intensity but also high sensitivity with the

A.M. El-Toni, D. Zhao and F. Zhang, Anal. Chem. 89

detection limit of 10.5 nM in aqueous solution.

(2017) 3492-3500.

Moreover, TbTATB has good biocompatibility so that it

[6]

2+

N. Lin, Q. Zhang, X. Xia, M. Liang, S. Zhang, L. Zheng and Q. Cao, RSC Adv. 7 (2017) 21446-

of living cells. This sensitive and selective sensor has the

21451.

in

[7]

biological systems. More significantly, this work would offer new possibilities for the design and use of stable

27 (2017) 357-367. [8]

lanthanide MOFs for sensing and imaging analytes in biological systems.

M.S. Kim, T.G. Jo, H.M. Ahn and C. Kim, J Fluoresc

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2+

potential to serve as a powerful indicator for Zn

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could carry out the goal of imaging Zn with the coexist

S. Lohar, S. Pal, M. Mukherjee, A. Maji, N. Demitri and P. Chattopadhyay, RSC Adv. 7 (2017) 25528-

M AN U

Acknowledgements

25534.

This work was supported by the National Natural Science Foundation of China (Nos. 51432001,

51472217, 51772268, 516320008, U1609219, and

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A porous and luminescent metal-organic framework containing triazine group for sensing and imaging of Zn2+

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Tianen Fan, Tifeng Xia, Qi Zhang, Yuanjing Cui*, Yu Yang, Guodong Qian*

Highlights

A porous and luminescent terbium MOF TbTATB has been designed and

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solvothermally synthesized.

TbTATB exhibited turn-on and exclusive sensing of Zn2+ with a detection limit of 10.5 nM.

•

TbTATB showed good biocompatibility and excellent imaging properties with the coexist of living cells.

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The turn-on mechanism was explored by luminescent lifetime and XPS spectrum.

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