A novel coumarin-based fluorescence chemosensor for Al3+ and its application in cell imaging

Article abstract of DOI:10.1016/j.saa.2018.11.006

As an efficient turn-on fluorescent chemosensor for Al³⁺, a new coumarin derivative (CND) has been designed and synthesized by the condensation of 8-formyl-7-hydroxycoumarin with niacin hydrazide. The spectroscopic studies revealed that the sensor CND exhibited a remarkable fluorescence enhancement towards Al³⁺ with high selectivity and sensitivity in EtOH-HEPES (95:5, v/v, pH = 7.40), which was attributed to the photoinduced electron transfer (PET) and –C[dbnd]N isomerization mechanism. Fluorescence titration calculations data showed that the detection limit and the association constants of CND for Al³⁺ were found to be 2.51 × 10^?7 M and 9.64 × 10⁴ M^?1, respectively. The results of experiments, including Job's plot, ¹H NMR titration and ESI-MS, revealed that the stoichiometric binding between CND and Al³⁺ was 1:1. The investigations of the pH dependency of CND for Al³⁺ detection, and the cell imaging suggested the sensor CND could be promisingly applied for the recognition of Al³⁺ in biological cells.

Full text of DOI:10.1016/j.saa.2018.11.006

Accepted Manuscript
A novel coumarin-based fluorescence chemosensor for Al3+ and
its application in cell imaging
Guohua Zhu, Yang Huang, Chun Wang, Linxia Lu, Tongming
Sun, Miao Wang, Yanfeng Tang, Doudou Shan, Shuijin Wen, Jinli
Zhu
PII:
DOI:
Reference:
S1386-1425(18)30997-1
https://doi.org/10.1016/j.saa.2018.11.006
SAA 16570
Spectrochimica Acta Part A: Molecular and Biomolecular
Spectroscopy
To appear in:
Received date: 11 October 2018
Revised date:
Accepted
date:
26 October 2018
3 November 2018
Please cite this article as: Guohua Zhu, Yang Huang, Chun Wang, Linxia Lu, Tongming
Sun, Miao Wang, Yanfeng Tang, Doudou Shan, Shuijin Wen, Jinli Zhu , A novel
coumarin-based fluorescence chemosensor for Al3+ and its application in cell imaging.
Saa (2018), https://doi.org/10.1016/j.saa.2018.11.006
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ACCEPTED MANUSCRIPT
A novel coumarin-based fluorescence chemosensor for Al3+ and its application in
cell imaging
Guohua Zhua, Yang Huangb, Chun Wangb, Linxia Lub, Tongming Suna, Miao Wanga,
Yanfeng Tanga,*, Doudou Shana, ShuijinWena and Jinli Zhua,
a.School of Chemistry and Chemical Engineering, Nantong University, Nantong 226019, P.R.
China
b.School of Textiles, Nantong University, Nantong 226019, P.R. China
Abstract: As an efficient turn-on fluorescent chemosensor for Al3+, a new coumarin
derivative (CND) has been designed and synthesized by the condensation of
8-formyl-7-hydroxycoumarin with niacin hydrazide. The spectroscopic studies
revealed that the sensor CND exhibited a remarkable fluorescence enhancement
towards Al3+ with high selectivity and sensitivity in EtOH-HEPES (95:5, v/v, pH =
7.40), which was attributed to the photoinduced electron transfer (PET) and -C=N
isomerization mechanism. Fluorescence titration calculations data showed that the
detection limit and the association constants of CND for Al3+ were found to be
2.51×10-7 M and 9.64×104 M-1, respectively. The results of experiments, including
1
Job,s plot, H NMR titration and ESI-MS, revealed that the stoichiometric binding
between CND and Al3+ was 1:1. The investigations of the pH dependency of CND for
Al3+ detection, and the cell imaging suggested the sensor CND could be promisingly
applied for the recognition of Al3+ in biological cells.
Keywords: Al3+, coumarin, chemosensor, live cells
1. Introduction
Corresponding authors
Email address:tangyf@ntu.edu.cn (Y.F. Tang), jinlizhu@ntu.edu.cn (J.L. Zhu).
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In the past few decades, fluorescent chemosensors for detecting transition metal ions
has attracted considerable attention due to their excellent selectivity, high sensitivity,
low cost, as well as on-site and real-time analysis [1-5], compared with traditional
detecting methods such as atomic absorption spectrometry [6], atomic emission
spectrometry [7], inductive coupled plasma-mass microprobe [8], electro chemical
methods [9]. Therefore, many researchers have been focusing on the development of
some efficient fluorescent probes for the recognition of metal ions.
Aluminum, as the third most abundant metal in the earth, is widely used in
aluminum-based medicines, water purification and many industrial fields including
food packaging, construction materials and cooking utensils, etc [10-13]. However,
unregulated and excessive Al3+ may cause serious damage to the human organs like
skeleton, kidney, liver, and may lead to various diseases such as Alzheimer,s disease,
Parkinson,s disease [14-17]. According to the World Health Organization (WHO), the
limit of permissible concentration of Al3+ in drinking water is only 7.41μM [18]. Thus,
it is of great demand for the development of fluorescent chemosensors for monitoring
Al3+ at very low concentrations. Up to now, numerous fluorescence chemosensors for
Al3+ have been developed based on different fluorescent dyes such as quinolone
[19-20], BODIPY [21-23] and coumarin [24-25]. Among them, coumarin derivatives
are frequently utilized as ideal acceptors in the design of fluorescent chemosensors
due to their low toxicity, good water solubility, high quantum yield and excellent
functionality [26-29]. At the same time, acylhydrazide schiff base could provide the
nitrogen-oxygen-rich binding sites for the target metal ion, suggesting that
acylhydrazide could be used as the one component for the synthesis of the fluorescent
chemosensors [30-32].
Herein, based on the above ideas and considering the cheapness, biocompatibility of
the nicotinic acid hydrazide, we designed and reported a simple coumarin-based
fluorescent chemosensor (CND), synthesized from 8-formyl-7-hydroxycoumarin with
niacin hydrazide shown in Scheme 1, As expected, the sensor CND displayed highly
selectivity towards Al3+ with no obvious disturbance from other metal ions in
EtOH-HEPES (95:5, v/v, pH = 7.40).
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O
HO
O
O
HO
O
O
a
N
O
1
d
HN
N
NH2
O
O
N
O
NH
O
OH
N
O
O
OH
b
c
N
CND
2
3
0
Scheme1. The route of synthesis for CND. a) urotropine, acetic acid, 90 C; b) MeOH,
o
concentrated sulfuric acid, 75 C; c) MeOH, hydrazine hydrate, room temperature; d) EtOH,
reflux.
2. Experimental Sections
2.1 Materials and general methods
Unless otherwise stated, all the solvents and reagents used are of analytical grade
from commercial suppliers and used as received. The salts used in stock solutions of
metal ions were HgCl2, Ni(NO3)2•6H2O, MgSO4, Ba(NO3)2, KNO3, AgNO3,
Mn(NO3)2, Pb(NO3)2, NaCl, CuCl2•2H2O, Al(NO3)3•9H2O, ZnCl2, CdCl2, CaCl2,
FeCl3•6H2O, Cr(NO3)3•9H2O, LiCl, FeCl2•4H2O, Co(NO3)2•6H2O. The water used
was ultra-filter deionized. The UV absorption and fluorescence emission spectra were
recorded on a TU-1901 Double-beam UV-Vis spectrophotometer and a F-7000
1
13
fluorescence spectrometer (Japan), respectively. H NMR and C NMR spectra were
recorded on a Bruker 400MHz NMR instrument with TMS as an internal standard.
FT-IR spectra were measured on a Thermo Fischer Nicolet IS50 FT-IR spectrometer
using KBr plates. High-resolution mass spectroscopy (HRMS) was measured on a
Bruker Thermo Scientific Q Exactive mass spectrometer. Fluorescence images of
cells were analyzed by Dual photon confocal microscope (Olympus FV1000 MPE).
2.2 Synthesis
2.2.1 Synthesis of 8-formyl-7-hydroxycoumarin (1): This synthesis was adapted
from literature [33]. 7-hydroxycoumarin (10 g, 61.7 mmol), urotropine (20 g, 142.6
mmol) and glacial acetic acid (75 mL) were mixed in a 500 mL flask and stirred at 90
oC for 8 h. Then 150 mL conc. HCl-H2O aqueous (84:100, v/v) was added, and the
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mixture was heated at 70 oC for another 30 min. After the reaction media was down to
room temperature, 300 mL cool water was added and the resulting solution was
extracted with ethyl acetate (4 ×100 mL). The organic phase was dried over Na2SO4.
The solvent was evaporated and the crude product was recrystallized from ethanol to
give the yellow solid 1. Yield: 2.14 g (18 %). IR (KBr, v in cm-1): 3410, 3076, 2917,
1747, 1645, 1599, 1222, 1180, 1107, 1000, 850.1H NMR (400 MHz, DMSO-d6):
11.91 (s, 1H), 10.43 (s, 1H), 8.02 (d, 1H, J = 9.56 Hz), 7.87 (d, 1H, J = 8.76 Hz), 6.95
(d, 1H, J = 8.8 Hz), 6.38 (d, 1H, J = 9.56 Hz). 13C NMR (100 MHz, DMSO-d6):
191.17, 164.23, 159.57, 156.10, 144.98, 136.50, 114.40, 113.04, 111.62, 109.66.
(Fig.S1, Fig.S2).
2.2.2 Synthesis of 2: This synthesis was adapted from literature [34]. Thionyl
chloride (9.52 g, 80 mmol) was added dropwise to a solution of nicotinic acid (5 g, 40
mmol) in methanol (100 mL) at -10 oC - 0 oC, then, the reaction mixture was refluxed
for 10 h. The solvent was evaporated and the distilled water (50 mL) was added. The
pH of the resulting solution was adjusted to 8-9 with Na2CO3, then the solution was
extracted with ethyl acetate (3 ×50 mL). The organic phase was dried over Na2SO4.
The solvent was evaporated and the crude product 2. The crude product 2 was directly
used in the next synthesis without characterization.
2.2.3 Synthesis of 3: Hydrazine hydrate (25 mL) was added to a solution of 2 (4 g,
9.2 mmol) in methanol (5 mL) at the room temperature. The solution was stirred
overnight at room temperature. The solvent was evaporated and the crude product was
recrystallized from ethanol to give the white solid 3. Yield: 2.69 g (67.3 %). IR (KBr,
v in cm-1): 3322, 3203, 3012, 2865, 1732, 1596, 1572, 1543, 1474, 1340, 952, 706. 1H
NMR (400 MHz, DMSO-d6): 10.05 (s, 1H), 9.05 (d, 1H, J = 1.6 Hz), 8.73 (dd, 1H, J1
= 1.6 Hz, J2 = 4.8 Hz), 8.22 (dt, 1H, J1 = 1.88 Hz, J2 = 7.96 Hz), 7.52 (dd, 1H, J1 =
4.84 Hz, J2 = 7.9 Hz), 4.68 (s, 2H). 13C NMR (100 MHz, DMSO-d6): 164.91, 152.20,
148.58, 135.15, 129.35, 123.92. (Fig.S3, Fig.S4).
2.2.4 Synthesis of CND: 8-formyl-7-hydroxycoumarin (1.9 g, 10 mmol) was first
dissolved in EtOH (10 mL), then compound 3 (1.37 g, 10 mmol) was added into the
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above solution. The resulting mixture was heated under reflux for 4 h. When the
solution was cooled to room temperature, a yellow solid was formed. The precipitate
was collected by filtration, washed with hot EtOH (2×10 mL) and recrystallized from
ethanol to give the yellow solid CND. Yield: 2.51 g (81.2 %). IR (KBr, v in cm-1):
3429, 3261, 3063, 1714, 1681, 1655, 1590, 1481, 1447, 1406, 1350, 1309, 1280, 1161,
833, 773, 700, 639. 1H NMR (400 MHz, DMSO-d6): 12.66 (s,1H), 12.60 (s,1H), 9.13
(s,1H), 9.11 (s,1H), 8.81 (d, 1H, J = 3.88 Hz), 8.32 (dt, 1H, J1 = 1.68 Hz, J2 = 8 Hz),
8.00 (d, 1H, J = 9.52 Hz), 7.67 (d, 1H, J = 8.64 Hz), 7.61 (dd, 1H, J1 = 4.84 Hz, J2 =
13
7.84 Hz), 6.96 (d, 1H, J = 8.64 Hz), 6.34 (d,1H, J = 9.52 Hz). C NMR (100 MHz,
DMSO-d6): 161.67, 161.63, 159.87, 153.67, 153.24, 149.15, 145.17, 144.33, 135.88,
131.82, 128.40, 124.20, 114.27, 112.61, 111.61, 105.93. HRMS: Calced for [CND +
Na]+, 332.06026; Found 332.06428. (Fig.S5, Fig.S6, Fig.S7).
2.3 Sample Preparation and Titration
Stock solutions of the salts were prepared in deionized water. The
concentrations were fixed to 1.0×10-2 M. Stock solution of the sensor CND (10-3 M)
were prepared in DMSO and then further diluted to 10-5 M in EtOH-HEPES (95:5, v/v,
pH = 7.40) for titration experiments. Every time an appropriate volume of each
analyte was added to the test solution. HEPES buffer was prepared in deionized water
by fixing to 2.0×10-2 M. The pH value of EtOH-HEPES (95:5, v/v) was adjusted to
7.40. UV and fluorescence spectra were monitored within 15 seconds.
2.4 Calculation of quantum yield
The fluorescence quantum yields of compounds was measured using quinine
sulfate as the standard (Φ=0.53, 0.1 M H2SO4) [35] and calculated using
I
unk
A
std
n
unk


unk
Φunk = Φstd× (
) × (
) × (
)2× (
)
(1)
I
std
A
unk
n
std
std
Where Φunk is the fluorescence quantum yield of the compound; Φstd is the
fluorescence quantum yield of quinine sulfate; Iunk and Istd are the integrated emission
intensities of the compound and the standard, respectively; Aunk and Astd are the
absorbances of the compound and the standard at the excitation wavelength,
respectively; nunk and nstd are the refractive indexes of the corresponding solution,
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respectively; λunk and λstd are the excitation wavelength of the compound and the
standard, respectively.
2.5 Calculation of association constants
The association constants of CND with Al3+ were calculated employing
Benesi-Hildebrand method [36-38] using equation (2), where K is the association
constant; I is the fluorescence intensity of the sensor CND; I0 is the fluorescence
intensity of the CND-Al3+ complex at 463 nm; and Ifc is the fluorescence intensity at
the saturation. If the plot of 1/ (I-I0) vs 1/ [Al3+] gave a linear fitting, it indicates a 1:1
stoichiometry between the sensor CND and Al3+.
1
1
1
(2)


(I  I0 ) (I  I fc) K(I  I fc)[Al3 ]
2.6 Cell culture and fluorescence imaging [39-41]
HepG-2 cells were seeded on 35 mm glass-bottomed dishes (NEST) and
incubated in RPMI-1640 in an incubator (37 °C, 5% CO2 and 20% O2) for 24 h. The
cells were washed slightly 3 times with fresh RPMI-1640. Subsequently, the cells
with different concentrations of the CND (0-20 μM) were incubated in 96 well-plates
for 24 h. After washing with fresh RPMI-1640, the cells pretreated with sensor CND
were further incubated with fresh RPMI-1640 containing 100 μM Al(NO3)3•9H2Ofor
15 min. Cells were then analyzed by Dual photon confocal microscope
(OlympusFV1000 MPE).
3. Results and Discussion
3.1 Fluorescent Sensing of Al3+
The fluorescence responses of the CND upon addition of different metal ions like
Al3+, K+, Pb2+, Cd2+, Cr3+, Na+, Ni2+, Li+, Ba2+, Ag+, Mg2+, Ca2+, Hg2+, Zn2+, Co2+,
Mn2+, Cu2+, Fe2+, Fe3+ were carried out in EtOH-HEPES (95:5, v/v, pH = 7.40) by
fluorescence spectroscopy. As depicted in Fig.1, most of the above metal ions did not
induce significant changes in intensity or any spectral shift of fluorescence spectra of
the sensor CND. In contrast, only the addition of Al3+ caused a strong fluorescence
emission enhancement (ca. 30 fold) at 463 nm, which could be attributed to the
photoinduced electron transfer (PET) and -C=N isomerization. As shown in Scheme 2,
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no obvious fluorescence emission of the free CND was observed due to PET
mechanism causing by lone pair electrons from the nitrogen atom of -CH=N to the
coumarin fluorophore and -C=N isomerization at the excited state [42-44]. After
coordinated with Al3+, the fluorescence emission intensity of the complex CND-Al3+
enhanced significantly resulting from the inhibition of PET and -C=N isomerization at
the excited state. In addition, the photography of the probe CND with different metal
ions under hand-held UV lamp also showed that it has a high selectivity towards Al3+
via blue emission (Fig.S8), indicating that the CND could be used to recognize Al3+
by naked eyes. The competitive experiments for Al3+ were also examined in the
presence of other metal ions under the same conditions. The histogram (Fig.2)
revealed that the fluorescence intensity of the CND-Al3+ were not significantly
influenced by other competitive metal ions, indicating that the CND could be used as
a fluorescence chemosensor with remarkably selectivity for Al3+ over other metal
ions.
3500
Al3+
2800
2100
K+, Pb2+, Cd2+, Cr3+, Na+, Ni2+,
1400
Li+, Ba2+, Ag+, Mg2+, Ca2+, Hg2+,
Zn2+, Co2+, Mn2+, Cu2+, Fe2+, Fe3+
700
and CND
0
400
440
480
520
560
600
Wavelength (nm)
Fig.1. The changes in fluorescence spectrum of the sensor CND (10 μM) in the presence of
various metal ions (100 μM) in EtOH-HEPES (95:5, v/v, pH = 7.40), λex= 348 nm.
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N
O
N
HN
N
HN
N
O
PET
Al3+
PET
Al3+
O
O
OH
O
O
O
Scheme 2. Mechanism of the sensor CND for the detection of Al3+.
CND + Mn+
CND + Mn+ + Al3+
3250
2600
1950
1300
650
0
Fig.2. Fluorescence intensity of the CND (10 μM) at 463 nm upon addition of various metal ions
(100 μM) in EtOH-HEPES (95:5, v/v, pH = 7.40). The black bars represent the fluorescence
intensity of the CND in the presence of other competitive metal ions, respectively. Red bars
represent the intensity after the subsequent addition of Al3+, λex= 348 nm.
In order to better evaluate the detecting properties of the CND towards Al3+, the
fluorescence titration was carried out by increasing concentrations of Al3+ in
EtOH-HEPES (95:5, v/v, pH = 7.40). Upon the gradual addition of concentrations of
Al3+ (0 - 230 μM) to the solution of the CND (10 μM), the fluorescence intensity at
463 nm presented a gradual increase (Fig.3), and the fluorescence quantum yield also
changed from 0.0091 to 0.0604. The detection limit of the CND for Al3+ was
calculated as low as 2.52×10-7 M according to the following equation [45-47]:
detection limit = 3 σ/κ, where σ is the standard deviation of blank measurements, and
κ is the slope between the fluorescence intensity versus sample concentration (Fig.S9).
At the same time, the Job's plot titration also confirmed 1:1 binding model between
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the CND and Al3+ with the association constant of 9.64×104 M-1 (Fig.4, Fig.S10).
These results indicated that the CND could be applied to monitor Al3+ quantitatively.
2200
2000
1800
23 eq
1600
1400
1200
1000
800
600
400
200
0
Al3+
0 eq
400
450
500
550
600
Wavelength(nm)
Fig.3. Fluorescence emission changes of the CND (10 μM) upon addition of different amount of
Al3+ (0-230μM) in EtOH-HEPES (95:5, v/v, pH = 7.40).
3000
2400
1800
1200
600
0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
[Al3+]/([CND]+[Al3+])
Fig.4. The Job,s plot of fluorescence intensity response of the CND at 463 nm to the mole fraction
of Al3+ in EtOH-HEPES (95:5, v/v, pH = 7.40).
3.2 Probable Binding mode of CND for Al3+
To further understand the interaction between the CND and Al3+, the UV-absorption
spectra changes of the CND upon the addition of different concentration of Al3+ were
monitored in EtOH-HEPES (95:5, v/v, pH = 7.40). As shown in Fig.5, it was
obviously seen that the intensity of the absorption bands of the CND enhanced at 340
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nm and decreased at 270 nm with gradual addition of Al3+. At the same time, the
presence of an isosbestic point at 317 nm clearly indicated the formation of complex
between CND and Al3+. Additionally, the binding site of the CND with Al3+ was also
1
investigated by H NMR titration. As depicted in Fig.6, upon the addition of Al3+ in
DMSO-d6 solution of the probe CND, the proton signals of the phenolic -OH (Ha) at
12.62 ppm disappeared gradually. The proton signals of the -N-H- (Hb) at 12.67 ppm
shifted to 12.71 ppm. At the same time, the proton signals of the -C=N- (Hc) at 9.13
ppm also shifted slightly while Al3+ existed. These results suggested that Al3+ may be
coordinated with the oxygen atom of the phenolic -OH, the oxygen of -C=O and the
nitrogen atom of -C=N-. Compared with the Fig.6 (3), there were no obvious
differences for the proton signals upon the addition of 2.0 equiv Al3+ (Fig.6 (4)),
which confirmed the 1:1 stoichiometry for CND to Al3+.The peak at m/z 397.8
-
(calculated for [CND + Al3+ + NO3 - H+] = 397.3) in the mass spectrum can be further
concluded that the binding model between CND and Al3+ may be 1:1 (Fig.7). This is
consistent with Job's plot and 1H NMR titration results.
13 eq
0.4
Al3+
0.3
0 eq
0 eq
Al3+
13 eq
0.2
0.1
260 280 300 320 340 360 380 400 420
Wavelength(nm)
Fig.5. Changes in the absorption spectra of the CND (10 μM) in EtOH-HEPES (95:5, v/v, pH =
7.40) after the addition of Al3+(0-13 equiv).
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Fig.6. 1H NMR titration plot of CND (1) with Al3+ ((2) = 0.5 equiv, (3) = 1 equiv and (4) = 2 equiv)
in DMSO-d6 solvent.
-
Fig.7. ESI Mass spectrum of CND-Al3+-NO3 complex.
3.3 pH effect of CND towards Al3+
Since pH of the solvent medium plays a vital role in the practical application of
fluorescence chemosensor under physiological conditions, the effect of pH on the
fluorescence intensity of the CND (10 μM) was investigated in the presence and
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absence of Al3+ (100 μM) in EtOH-HEPES (95:5, v/v, pH = 7.40). These experiments
were carried out in the pH range from 2 to 11. As shown in Fig.8, it was found that the
overall fluorescence intensity of the CND-Al3+ was always higher than the free
receptor CND and did not have any significant changes in the range of pH 2-11,
which confirmed that CND-Al3+ complex are steady in this wide pH range (2-11).
These results clearly suggested that CND can be used as Al3+chemosensor for
biological applications.
CND
CND+ Al3+
4000
3200
2400
1600
800
0
2
4
6
8
10
pH
Fig.8.Effect of pH on fluorescence intensity of the CND (10 μM) and CND with 10 equiv of Al3+
in EtOH-HEPES (95:5, v/v, pH = 7.40). λex= 348 nm, λem= 460 nm.
3.4. Bio imaging
As shown in Fig.9, MTT assay [45-46] revealed that the viability of the HepG-2
cells was greater than 80 % at high concentration of CND up to 200 μM, which
indicated that the sensor CND has low toxicity to the HepG-2 cells. In addition, the
practical application of CND in biological systems was investigated by cell-imaging
experiments [39]. As shown in Fig.10 (a), the HepG-2 cells with 10 μM of the CND
o
were incubated at 37 C for 24 h, and no detectable fluorescence appeared. It can be
seen that a blue fluorescence in cells was observed significantly by dual photon
confocal microscope after the cells were further incubated with fresh RPMI-1640
containing 100 μM Al3+ for 15 min (Fig.6 (c)). An overlay of the bright field and
fluorescence image also confirmed that the CND was cell membrane permeable
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(Fig.10 (b), (c)). These studies indicated that the sensor CND could be capable of
recognizing intracellular Al3+ as a promising fluorescence chemosensor.
100
80
60
40
20
0
0
5
10
15
20
Concentration (10-5 M)
Fig.9.Cell viability of HepG-2 cells treated with various concentration (0 - 200 μM) of the sensor
CND determined by MTT assay.
Fig.10. (a) fluorescence image of HepG-2 cells incubated with CND (10 μM); (b) bright field
images after presence of Al3+ (100 μM); (c) fluorescence images after presence of Al3+ (100 μM).
4. Conclusions
In conclusion, a new coumarin-based fluorescence chemosensor CND for the highly
selective detection of Al3+ over other metal ions was developed. The configuration of
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1
a 1:1 CND-Al3+ complex was well determined by H NMR, ESI-MS and Job's plot.
The sensor CND had a good potential application because of its excellent selectivity
and high sensitivity, wide range of pH (2-11) and very low detection limit (2.52×10-7
M). And more importantly, due to its low toxicity, bio-imaging study also revealed
that the CND can be successfully applied to monitor Al3+ in live cells. These results
indicated that the sensor CND can be a good candidate for selective recognizing Al3+
in biological environment.
Acknowledgements
This work was supported by National Natural Science Foundation of China
(No. 21476117, 21776140, 21501100) and High-level Talents in Six Industries
of Jiangsu Province (XCL-062). We also thanked Analysis and Testing Center
of Nantong University for their testing support.
Supporting information
Detailed the experimental methods and characterizations can be found in the
supporting information.
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Graphical abstract
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Highlights
1. A novel coumarin-based fluorescence sensor for Al3+ was designed and
synthesized.
2. This sensor has good selectivity and sensitivity for Al3+.
3. This sensor can be applied in live cells.
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