Highly selective fluorescent probe based on a rhodamine B and furan-2-carbonyl chloride conjugate for detection of Fe3+ in cells

Article abstract of DOI:10.1016/j.tetlet.2018.09.003

A furan-2-carbonyl chloride modified rhodamine B derivative (RBFC) has been designed and synthesized. The probe RBFC exhibited excellent sensitivity and selectivity for detection of Fe³⁺ with a 1:1 stoichiometry over other tested metal ions in a MeOH/H₂O (1:1, v/v, pH 7.36, HEPES buffer, 1.3 mM) solution. The association constant and the detection limit were calculated to be 7.28 × 10³ M^?1 and 0.437 μM based on fluorescence titration analysis. Furthermore, the probe RBFC was successfully applied in living cells, and the results indicated that the probe could monitor intracellular Fe³⁺ in MCF-7 cells.

Full text of DOI:10.1016/j.tetlet.2018.09.003

Accepted Manuscript
Highly Selective Fluorescent Probe Based on a rhodamine B and furan-2-car-
3
+
bonyl chloride conjugate for Detection of Fe in Cells
Yu Wang, Fan Song, Jing Zhu, Yuqi Zhang, Lei Du, Chun Kan
PII:
S0040-4039(18)31075-X
https://doi.org/10.1016/j.tetlet.2018.09.003
TETL 50242
DOI:
Reference:
To appear in:
Tetrahedron Letters
Received Date:
Revised Date:
Accepted Date:
28 June 2018
15 August 2018
1 September 2018
Please cite this article as: Wang, Y., Song, F., Zhu, J., Zhang, Y., Du, L., Kan, C., Highly Selective Fluorescent
3
+
Probe Based on a rhodamine B and furan-2-carbonyl chloride conjugate for Detection of Fe in Cells, Tetrahedron
Letters (2018), doi: https://doi.org/10.1016/j.tetlet.2018.09.003
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Highly Selective Fluorescent Probe Based on a rhodamine B and
3
+
furan-2-carbonyl chloride conjugate for Detection of Fe in Cells
a
a
b
c
a
a,*
Yu Wang , Fan Song , Jing Zhu , Yuqi Zhang , Lei Du , Chun Kan
a
College of Science, Nanjing Forestry University, Nanjing 210037, PR China
b
Jiangsu Key Laboratory for Pharmacology and Safety Evaluation of Chinese Materia
Medica, Department of Pharmacy, Nanjing University of Chinese Medicine,
Nanjing 210023, PR China
c
Cambridge International Centre Daqing No.1 Middle School, Daqing 163453, PR
China
⃰
Corresponding author.
Email: Kanchun@njfu.edu.cn

Abstract
A furan-2-carbonyl chloride modified rhodamine B derivative (RBFC) has been
designed and synthesized. The probe RBFC exhibited excellent sensitivity and
3
+
selectivity for detection of Fe with a 1:1 stoichiometry over other tested metal ions
in a MeOH/H O (1:1, v/v, pH 7.36, HEPES buffer, 1.3 mM) solution. The association
2
3
-1
constant and the detection limit were calculated to be 7.28×10 M and 0.437 μM
based on fluorescence titration analysis. Furthermore, the probe RBFC was
successfully applied in living cells, and the results indicated that the probe could
3
+
monitor intracellular Fe in MCF-7 cells.
Key words: fluorescent Probe; rhodamine B; furan-2-carbonyl chloride; iron ions;
MCF-7 cells

1
. Introduction
Iron is a relatively rich metal element on the earth, which accounts for about 4.1%
of its total. Iron not only plays an important role in the modern society, but even more
importantly, although iron is a trace element in the human body, but it is the most
important of the more than 10 elements necessary in the human body. Therefore, the
[
1]
iron plays the key role for the health of the human body . Iron is widely distributed
in the human body. Almost all tissues and organs contain, including blood, muscle
tissue, spleen, liver and bone marrow. Iron is an important component of hemoglobin,
myoglobin and various enzymes. Therefore, it is an essential trace element in human
physiological activities, such as cell metabolism, oxygen metabolism, electron
transfer, enzyme catalyzed DNA and RNA synthesis, proton transfer, maintenance of
[
2-6]
intracellular acid-base balance and osmotic pressure regulation
. When the iron
content in the human body deviates from normal level or abnormal distribution, it will
endanger human health. Insufficient or excessive iron content in human body can
damage the normal physiological functions, such as immunosuppression, decrease in
[
7]
intelligence, reducing the ability of human body to resist infection, and so on , and
[
8]
[9]
even a variety of diseases, such as abnormal liver function , myocardial injury
,
[
10]
[11]
[12]
osteoporosis , diabetes , and cancer . Therefore, real-time monitoring of iron
ions is of great importance to the health of organisms and human beings.
[
13]
At present, conventional methods like atomic absorption spectroscopy (AAS)
,
[
14]
[15]
colorimetry,
voltammetry,
and inductively coupled plasma mass spectrometry
[
16]
3+
(
ICP-MS)
had been used for the detection of Fe . However, due to their high cost
and complex sample pretreatment, the above methods fail to popularized use.
Fluorescent molecular probes are used for the detection of metal ions because of their
simple synthesis methods, few sample requirements, short response time, good
[
17-21]
3+
selectivity and high sensitivity
. Most of the known Fe sensors are based on
3
+
fluorescence quenching mechanisms due to the paramagnetic nature of Fe ions
[
22]
which are not as sensitive as a fluorescence enhancement response.
As a result,
3
+
fluorescence-enhanced probes would be more desirable for Fe detection. Rhodamine
B is one of the most commonly used dye which has attracted much attention duo to its
excellent photophysical properties, such as long absorption and emission wavelengths

extended to the visible region, high fluorescence quantum yield and large extinction
[
23-25]
coefficient.
Many fluorescence probes based on Rhodamine B and its derivatives
2
+
2+
2+
3+
3+
2+ [26-31]
have been developed for Hg , Cu , Zn , Cr , Al and Pb .
Herein we have synthesized a fluorescent probe RBFC by combining rhodamine
B and furacyl chloride with ethylenediamine. The experimental results show that the
3
+
probe RBFC has a good detection effect on the specific identification of Fe in the
solution of EtOH/HEPES (1:1, v/v, 1.3mM, pH=7.36). The cytotoxicity of the human
breast cancer cell (MCF-7) is very low and the effect of cell imaging is very good.
3
+
Therefore, the probe RBFC monitor intracellular Fe in the living cells.
Figure.1 Chemical structure of RBFC
2
. Result and discussion
2
.1.Synthesis of RBFC
The synthesis procedure of RBFC was shown in Scheme. 1. Compound 1 was
prepared in 92% yield by refluxing commercially available rhodamine B with ethane
1,2-diamine in EtOH. Then the probe RBFC was isolated from the reaction of
-
compound 1 and N-(Methylaminopyridine) chloroacetamide in EtOH with a good
1
yield (64%). The structure of intermediate and RBFC were confirmed by H NMR,
1
3
C NMR and HRMS (Supporting materials).
Scheme.1 Synthesis procedure of RBFC

2
.2. Effect of pH and response of time
Fluorescence spectra of probe RBFC were inspected at different pH values
(Figure. 2). Upon excitation at 560 nm, the probe showed almost no fluorescence in a
wide pH range (6.0~11.0). Along with the pH varied from 6.0 to 2.0, an emission peak
evolved at 582 nm and the fluorescence intensity enhanced gradually. The significant
fluorescence increase was ascribed to the ring-opening process of rhodamine
+
spirolactam of RBFC caused by H . These results suggested that RBFC was
insensitive to pH from 6.0 to 11.0 and could work well in approximate physiological
conditions with low background fluorescence. Therefore, the EtOH/HEPES buffer
(1:1, v/v, 1.3 mM, pH=7.36) solution was chosen for the following experiments. In
3
+
addition, the time course of RBFC to 5 equiv of Fe was conducted. The fluorescence
intensity of RBFC at 582 nm was increased with standing time and leveled off within
7
0 min (Figure. 3).
Figure. 2 The effect of the pH on the fluorescence of RBFC (0.02 mM) in MeOH/H O solutions
2
(1:1, v/v). The excitation and emission wavelengths were 560 nm and 582 nm.

3
+
Figure.3 Fluorescence spectra of RBFC (0.02mM) with Fe (0.1mM) in MeOH/H O (1 : 1, v/v,
2
pH 7.36, HEPES buffer, 1.3mM) solutions. The excitation and emission wavelengths were 560
and 582 nm. Inset: plot of fluorescence intensity at 582 nm over a period of 90 min.
2
.3. UV-vis absorption and fluorescence spectra of RBFC toward
3
+
Fe
The photophysical properties of RBFC was evaluated in MeOH/HEPES buffer
1:1, v/v, 1.3 mM, pH=7.36) solution in the presence of different various metal icons.
As shown in Figure. 4, compound RBFC (0.02mM) showed a strong absorption at
(
3+
2+
2+
2+
2+
2+
2+
2+
2+
around 320 nm. Additions of Cr , Cu , Mg , Cd , Fe , Ni , Mn , Co , Hg ,
2
+
2+
2+
+
Ba , Ca , Zn , K and other metal icons showed little or no effect on the absorption
3
+
3+
of RBFC besides Fe . Upon addition of 5 equiv Fe ions, a new absorption peak
centered at 558 nm appeared because of the rhodamine B ring-opening process. (The
2
-1
-1
3
-1
-1
molar absorption coefficient raises from 1.0*10 M *cm to 1.0*10 M *cm .) The
above result induced a clear colorimetric change from colorless to pink. Such a
dramatic color change demonstrated that the RBFC as a sensitive “off-on” and
3
+
colorimetric probe for Fe .

Fluorescence spectra of probe RBFC were also inspected in the presence of
different various metal icons. As shown in Figure. 5, when excited with 560 nm, there
was almost non fluorescence due to its ring-closed spirolactam structure. With
3
+
addition of 5 equiv of Fe , around 28-fold fluorescence enhancement at 582 nm was
3
+
2+
2+
2+
2+
2+
2+
obviously observed. However additions of Cr , Cu , Mg , Cd , Fe , Ni , Mn ,
2
+
2+
2+
2+
2+
+
Co , Hg , Ba , Ca , Zn , K and other metal icons exerted a slight enhancement or
quenching effect on the emission of RBFC. Commonly, the fluorescence intensity at
around 550 nm would be enhanced because of the rhodamine B ring-opening process.
Those indicated the compound RBFC can serve as a highly selective fluorescent and
3
+
colorimetric probe for Fe detection in MeOH/HEPES buffer (1:1, v/v, 1.3 mM,
pH=7.36) solution.
3
+
To further explore selectivity of RBFC toward Fe , the metal ions competence
3
+
assay was carried out by adding Fe into the probe RBFC solution in the presence of
3
+
other metal ions. As depicted in Figure.6, the binding of Fe by RBFC was hardly
interfere by other commonly coexistent ions, which further indicated that the probe
3
+
RBFC was selective and sensitive for detection of Fe . Additionally, the competitive
3
+
selectivity of RBFC for Fe under identical conditions was examined in the presence
3
+
of other anions. As shown in Figure.7, the emission of RBFC with Fe shows no
-
-
-
-
significant change when introducing various anions, including I , F , Br , H PO ,
2
4
2
-
-
2-
-
2-
2-
HPO , BrO , S , NO , SO , and S O . These results further demonstrate that the
4
3
3
4
2
8
3
+
presence of anions does not markedly interfere with the detection of Fe .

Figure.4 UV–vis absorption spectra of RBFC (0.02mM) in MeOH/H O (1:1, v/v, pH 7.36,
2
HEPES buffer, 1.3mM) solutions upon addition of 5 equiv. of various metal icons. Each spectrum
was recorded 90 min after the addition of the metal ions.
Figure. 5 Fluorescence spectra of RBFC (0.02mM in MeOH/H O (1:1, v/v, pH 7.36, HEPES
2
buffer, 1.3mM) solutions upon addition of 5 equiv. of various metal icons with excitation at 582
nm. Each spectrum was recorded 90 min after the addition of the metal ions.

Figure. 6 Metal ion selectivity profiles of RBFC (0.02mM) in the presence of various metal ions
in MeOH/H O (1:1, v/v, pH 7.36, HEPES buffer, 1.3mM) solution. Black bars represent the
2
fluorescence intensity (582 nm) of RBFC in the presence of 5 equiv of other ions in the absence of
3
+
Fe . Red bars represent the fluorescence intensity (582 nm) in the presence of various metal ions
3+
after the addition of Fe . Each spectrum was recorded 90 min after the addition of the metal ions.
Figure. 7 Fluorescence spectra of RBFC (0.02mM in MeOH/H O (1:1, v/v, pH 7.36, HEPES
2
3
+
buffer, 1.3mM) solutions upon addition of 5 equiv. of Fe and 5 equiv. of various anions icons
with excitation at 582 nm. Each spectrum was recorded 90 min after the addition of the metal ions.

2
.4. Fluorescence spectral titrations
3
+
To get a further insight into the binding of Fe with RBFC, the absorbance
3
+
spectra of RBFC upon titration with Fe in MeOH/HEPES buffer (1:1, v/v, 1.3mM,
pH=7.36) solution were recorded (Figure. 8). Upon addition of increasing amounts of
3
+
Fe ions, a new absorption band centered at 582 nm appeared with increasing
3
+
intensity. Plotting fluorescence intensity at 582 nm verse Fe concentration (3~25μM)
afforded a good linear relationship (R=0.98001). According the equation DL=3S/δ,
3
+
the detection of RBFC for Fe was 0.437μM (Figure. 9). And the binding constant
3
+
3
-1
of RBFC with Fe calculated to be 7.28×10 M (pKa= -3.86) from the fluorescence
spectral titrations, according to the Benesi-Hildebrand equation (Figure. 10).
Figure. 8 Fluorescence spectra of 60μL RBFC (1mM) in 3.0mL MeOH/H O (1:1, v/v, pH=7.36,
2
3
+
HEPES buffer, 1.3mM) solutions at various equiv of Fe (0-120equiv). The excitation and
emission wavelengths were 560 and 582 nm. Inset: the figure on the right displays the
3
+
fluorescence intensity at 582 nm vs. the Fe concentration. Each spectrum was recorded 90 min
after the addition of the metal ions.

Figure. 9 Fluorescence intensity at 582 nm of RBFC (0.02mM) in MeOH-H O solution (1:1, v/v,
2
3
+
pH 7.36, HEPES buffer, 1.3mM) with different amounts of Fe . Each spectrum was recorded 90
min after the addition of the metal ions.
3
+
Figure. 10 Benesi–Hildebrand plot (λ =582 nm) of 1/(F−F ) vs. 1/[Fe ] based on a 1:1
em
0
3
+
association stoichiometry between sensor RBFC and Fe . Each spectrum was recorded 90 min
after the addition of the metal ions.

2
.5. Proposed sensing mechanism
3
+
The stoichiometry of a binding event between Fe and the RBFC probe was
determined to investigate this mechanism. As showed in Figure.11, Job’s plot (Figure.
3
+
1
1) confirmed the 1:1 stoichiometry for the RBFC-Fe complex with an approximate
maximum at a mole fraction of 0.5.
Figure. 11 Job plot of RBFC in MeOH/H O (1:1, v/v, pH 7.36, HEPES buffer, 1.3mM) solution
2
3
+
with a total concentration of [RBFC]+[Fe ] =50μM. The emission wavelength was 582 nm
λex=560 nm). Each spectrum was recorded 90 min after the addition of the metal ions.
(
3
+
To further elucidate the binding mode of RBFC with Fe , 1H NMR spectra of
3
+
RBFC in the presence and absence of Fe were studied. As shown in Figure.12, The
3
+
addition of 0.2 equiv. Fe into RBFC in CD OD:D O (5:1, v/v) solution led to an
3
2
obvious blue shift of the signals of protons H , H (H : from the peak centered at 6.50
e
f
e
ppm to 6.93 ppm, Δδ = 0.43 ppm; H : from the peak centered at 6.26 ppm to 6.50 ppm,
f
Δδ = 0.24 ppm). This was due to the decrease in electron density of the aromatic ring,
3
+
which proved the delocalization of xanthenes, that is, Fe induced the opening of the
spirocycle. Next, the proton signals of H , H , H apparent obvious shifts (H , H :
l
m
n
l
n
from the peak centered at 7.39 ppm to 7.53 ppm, Δδ = 0.14 ppm; H : from the peak
m
centered at 6.21ppm to 6.48pm, Δδ = 0.27ppm). The results indicated that the “O”
atoms on the furan group in the string of RBFC participated in the coordination with

3
+
Fe . Herein, according to above experimental result, we broached a conceivable
3
+
3+
mechanism of Fe complex with RBFC (Scheme. 2), in which Fe may be
coordinated with the oxygen atom of the amide, the oxygen atom of the carbonyl and
the oxygen atom of the furan group.
1
Figure. 12 H NMR spectra (500 MHz, 298K, CD OD/D O (5:1,v/v)) of RBFC, and
3
2
3+
RBFC+0.2equiv Fe . Each spectrum was recorded 90 min after the addition of the metal ions.
3
+
Scheme. 2 Proposed mechanism for the binding of compound RBFC to Fe .

2
.6. Fluorescence imaging in living cells
Finally, to investigate the potential biological application of the probe RBFC in
living cells, imaging inside MCF-7 cells were monitored by florescence microscopy.
To begin with, the cytotoxicity of probe RBFC was evaluated using a
conventional MTT assay. As shown in Figure. 13, when MCF-7 cells are treated with
probe RBFC at a concentration of no more than 30 μM for 24 h, no significant
cytotoxic response (cell viability ≥85%) is observed. Thereby, 10 μM of probe
RBFC is used for cell imaging.
Then fluorescence imaging of RBFC was conducted in MCF-7 cells. Bright-field
measurements after the treatment with RBFC confirmed that the cells were viable
throughout the imaging experiments. As shown in Figure.14A2, RBFC cells display
3
+
almost no fluorescence. The cells treated with both the Fe and probe RBFC exhibit
strong fluorescence (shown in Figure.14C2), while the cells treated only with probe
RBFC show weak fluorescence (shown in Figure.14B2). These results indicated that
probe RBFC is cell membrane-permeable, effective intracellular imaging agent for
3
+
Fe ions, and valuable for studying the uptake, bioaccumulation, and bioavailability
3
+
of Fe in living organisms.
Figure. 13 Cytotoxic effect of RBFC in MCF-7 cells incubated for 24 h.

3
+
Figure.14 Fluorescence images of MCF-7 cells incubated with RBFC and/or Fe . MCF-7 cells
were incubated with 100 μM FeCl for 60 min at 37 °C, followed by 10 μM RBFC for additional 5
3
h. (A) Fluorescence image of MCF-7 Cells; (B)Cells treated with only probe RBFC; (C)Cells
incubated with FeCl for 1h,followed by treatment with probe RBFC for an additional 5h;(1)
3
Bright field .(2) Red channel.
3
. Conclusion
3
+
In summary, we developed a fluorescent probe RBFC for sensing Fe based on
3
+
rhodamine derivative. The probe could specifically recognize Fe in a MeOH/H O
2
(1:1, v/v, pH 7.36, HEPES buffer, 1.3mM) solution by UV–vis and fluorescence
response. The probe RBFC displayed a 28-fold fluorescence enhancement upon
3
+
3+
complexation with Fe under in vitro. The detection limit of the probe RBFC for Fe
3
-1
was calculated to be 0.437μM and the association constant was 7.28×10 M . The
3
+
probe was site-specifically internalized in Fe due to the opening of the spirolactam
3+
rings occurs upon RBFC coordination with Fe . Additionally, the probe has been
3
+
applied to the microscopic imaging for monitor intracellular Fe in MCF-7 cells with
little cytotoxity.
4
. Experimental

4
4
.1．Materials and instruments
For details, see the Supporting Information.
.2. Synthesis of 2-(2-aminoethyl)-30,60-bis(diethylamino)spiro-[isoindoline-1,90-
xanthen]-3-one (compound 1)
Syntheses and characterizations of compound 1 were described in Supporting
Information.
4
.3. Synthesis of RBFC
A mixture of compound 1 (174.2 mg, 0.36 mmol), furan-2-carbonyl chloride
(0.03 mL, 0.30 mmol) and triethylamine (0.05mL, 0.36mmol) were dissolved in
EtOH (5.0mL) with stirring at room temperature under nitrogen for 4 h. After
completion of the reaction, the solvent was removed under reduced pressure. The
residue was purified by flash silica gel column chromatography using MeOH–CH Cl
2
2
(2:98, v/v), yielding a pink solid RBFC (112.0 mg, 64%).
1
H NMR (CDCl ), δ 8.02（s, 1H, N-H), 7.94(m, 1H, Ar-H), 7.59(m, 1H, Ar-H),
3
7
.44(m, 2H, Ar-H), 7.09(m, 1H, Ar-H), 7.05(d, J=3.5, Ar-H, 1H), 6.45(m, 3H), 6.38(d,
J=2, 2H), 6.27(dd, J =2, J =8.5, 2H), 3.40(t, J=5, 2H), 3.35(q, J=7, 8H), 3.21(q, J=4.5,
1
2
1
3
2
1
H), 1.29(m, 2H), 1.18(t, J=7, 12H) ppm. C NMR (CDCl ), δ 170.15, 158.64,
3
54.05, 153.42, 149.08, 148.41, 144.24, 132.90, 130.58, 128.41, 124.03, 123.07,
113.55, 111.73, 108.41, 104.85, 97.92, 77.16, 65.87, 44.49, 40.41, 29.82, 12.74 ppm.
FTMS（M）found，579.2939，calculated for C H N O ，579.2893.
3
5
39
4
4
4
.4. General spectroscopic procedures
Stock solutions (5.0mM) of the metal chloride salts or nitrate of (Fe , Cr , Cu ,
3
+
3+
2+
2
+
2+
2+
2+
2+
2+
2+
2+
2+
2+
+
+
Mg , Cd , Fe , Ni , Mn , Co , Hg , Ba , Ca , Zn , K , Na ) in water were
prepared. Stock solutions of RBFC (1.0mM) were prepared in MeOH/H O (1:1, v/v, pH
2
7.36, HEPES buffer, 1.3mM). All spectra were recorded 90min after the addition at room
temperature with the excitation wavelength set at 560 nm and emission was collected
from 564 to 702 nm (excitation /emission slit widths: 2 nm)
4
.5. Calculations for the detection limit and the binding association constant
Calculations for the detection limit and the binding association constant were
described in Supporting Information.
.6. Cell studies of RBFC in the presence of Fe
MCF-7 cells were incubated in Dulbecco`s modified Eagle`s medium (high
glucose, HyClone) supplemented with 15% FBS (fetal bovine serum), 100 units/mL
3
+
4

penicillin, and 100 units/mL streptomycin in a 5% CO /95% air incubator at 37 ℃.
2
4
The MCF-7 cells (2×10 cells per well) were seeded into 24 well plates overnight
before imaging. Then the cells were incubated with 10 μM RBFC in culture medium
for 4 h in an air incubator at 37 ℃. In the control experiment, cells were pretreated
3
+
with 100 μM Fe for 1 h and then incubated with 10 μM RBFC in culture medium
for an additional 4 h. After washing triple with PBS, the cells was imaged under an
inverted fluorescence microscope with the red channel.
4
.7. Cell cytotoxicity assay
To determine the cell viability of RBFC, MTT (3-(4,5-dimethyl-2-thiazolyl)
-2,5-diphenyl-2-H-tetrazolium bromide) assay was performed according to the
3
procedure described. MCF-7 cells (6×10 cells per well) were cultured in a 96 well
plate at 37 ℃, and exposed to varying concentrations of RBFC (5, 10, 20, 30, 40, 60
-1
and 80 μM) respectively, for 24 h. 50 μL of MTT solution (1 mg ml ) was added to
each well of a 96-well culture plate and incubated again at 37 ℃ for a period of 4 h.
All media were removed from wells and DMSO (150 μL/well) was added to dissolve
the formazan. Absorbance was measured at 550 nm with a microplate reader (Infinite
M200 Pro). All experiments were performed in quadruplicate and the relative cell
viability (%) was expressed as a percentage relative to the untreated control cells.
Acknowledgements
This research was supported by the National Natural Science Foundation of China
(50772048), Jiangsu Six Talent Peak Award (2015, Prof. Jing Zhu), Natural science
fund for colleges and universities in Jiangsu Province (09KJD430007), Scientific
Research Foundation of Nanjing Forestry University. Undergraduate Scientific and
Technological Innovation Project of Nanjing Forestry University.
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Highlights
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A fluorescent probe synthesized with rhodamine B and furan-2-carbonyl chloride
3
+
The probe exhibited a high selectivity and sensitivity towards Fe in solution
UV-vis absorption and fluorescence spectroscopic are used to characterize the probe
3
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The probe could be applied to monitor intracellular Fe in living cells

A furan-2-carbonyl chloride modified rhodamine B derivative has been designed and
synthesized. The probe exhibited excellent sensitivity and selectivity for detection of
3
+
3+
Fe in a MeOH/H O solution. And it could monitor intracellular Fe in MCF-7 cells.
2