Chromogenic and fluorogenic "off-on-off" chemosensor for selective and sensitive detection of aluminum (Al3+) and bifluoride (HF2-) ions in solution and in living Hep G2 cells: Synthesis, experimental and theoretical studies

Article abstract of DOI:10.1039/d0nj02117b

A simple pyridine-dicarbohydrazide based colorimetric and fluorometric chemosensor L was designed and synthesized for Al3+ ion sensing in organo aqueous solution. In the presence of Al3+ ions, probe L exhibited visible color changes and fluorescence enhancement (20-fold) due to Al3+ induced chelation-enhanced fluorescence (CHEF) effects. Chemosensor L revealed high selectivity toward Al3+ ions by "turn-on"fluorescence among the other competitive metal ions examined with a detection limit of 0.8 μM. Probe L was found to bind with Al3+ ions in a 1 : 2 (probe : metal) stoichiometric fashion, with an association constant (Ka) of 4.26 × 104 M-2. In addition, DFT and TDDFT calculations were carried out to recognize the binding nature and electronic properties of probe L and its Al-complex. Furthermore, the in situ prepared [L-Al] complex was able to detect HF2- anions via a metal displacement strategy. The bioimaging application of Al3+ and HF2- was implemented in living human liver cancer cells (Hep G2). This journal is

Full text of DOI:10.1039/d0nj02117b

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Chromogenic and fluorogenic “off-on-off” chemosensor for selective and sensitive
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detection of aluminum (Al3+) and bifluoride (HF2 ) ions in solution and in living
HepG2 cells: synthesis, experimental and theoretical studies
5
Samit Pramanik,a Saikat Kumar Manna,b Sudipta Pathak,b,* Debasish Mondal,c Kunal Pal,d and
Subrata Mukhopadhyay a
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
A simple pyridine-dicarbohydrazide based colorimetric and fluorometric chemosensor L was designed and synthesized for Al3+ ions
10 sensing in organo aqueous solution. In presence of Al3+ ions, probe L exhibited visible color changes and fluorescence enhancement (20-
fold) due to Al3+ induced chelation-enhanced fluorescence (CHEF) effects. The chemosensor L revealed high selectivity toward Al3+ ions
by “turn-on” fluorescence among the other competitive metal ions examined with a detection limit of 0.8µM. The probe L was found to
bind with Al3+ ions in a 1: 2 (probe: metal) stoichiometric fashion, with the association constant (Ka) of 4.26 × 104 M-1. In addition, DFT
and TDDFT calculations were carried out to recognize the binding nature and electronic properties of the probe L and its Al-complex.
-
15 Furthermore, in situ prepared [L-Al] complex was able to detect HF2 anions via a metal displacement strategy. The bioimaging
application of Al3+ and HF2- were implemented in the living human liver cancer cells (Hep G2).
detection of aluminum ion is imperative in various samples
connected to environment, foodstuff, medicine, etc. But detection
Introduction
of aluminium ion is still a major challenge due to its low
20 Being the third most abundant (8.3% by weight) element (after
coordination capability, high hydration aptitude and the lack of
oxygen and silicon) on the surface of the earth, aluminum is
45 spectroscopic features.11 A number of analytical techniques have
widely attached with our daily contemporary life in the form of
been used for the detection of aluminum ions, such as atomic
food packaging, water purification, cooking utensils,
absorption spectrometry,12 inductively coupled plasma atomic
pharmaceuticals, manufacturing of computers, etc.1-3 Aluminium
emission spectrometry (ICP-AES),13-14 inductively coupled
25 compounds are also extensively used in paper industry, in dye
plasma mass spectrometry (ICP-MS),15 nanoparticle-based
production, in textile industry, as a component of many cosmetic
50 sensors,16 ion selective membrane,17 electrochemical methods,18
preparations and currently utilized in alimentary industry and in
and several other methods.19 But these techniques are restricted to
many more.4-5 Therefore, there is a good chance of accumulation
the laboratory because of high equipment cost, time consuming
of aluminum ion (Al3+) in food chain and toxicity towards human
and necessity for trained personnel. However, spectrofluorimetry
30 health. But, the tolerable daily intake of aluminum is about (3–
is superior in terms of quick analysis, high selectivity, sensitivity
10) mg and consequently upper limit of aluminum nutritional
55 and ease of operation. As Al3+ is a hard acid, it prefers hard base
intake is about 7 mg/kg-1 per week of the body weight according
donor sites for coordination,20 so the Schiff base probes with N
to the WHO report.6 Excess accumulation of this metal causes
and O donor centres could be used as good ligands for Al3+
some serious diseases like myopathy, Parkinson’s disease,
detection.21 In several research fields hydrazides have been
35 Alzheimer’s disease, osteoporosis, headaches, anemia, chronic
extensively used as ligands due to their facile syntheses, tunable
renal failure, dialysis encephalopathy, bone softening, kidney
60 electronic properties and good chelating capability.22 In this
damage and even breast cancer.7-9 The solubility of aluminium
work, we have designed and synthesized
dicarbohydrazide based ‘turn-on’ chemosensors L which show
high selectivity for Al3+ with low detection limit (LOD).
a
pyridine-
minerals at lower pH increases the amount of available Al3+,
which can affect plant’s normal growth and development,
40 ultimately hampering agricultural production.10 Therefore, easy
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Anions play a vital role in the area of supramolecular chemistry,
especially in environmental, chemical, medical and biological 40 monitoring absorption and fluorescence changes in presence of
The spectroscopic properties of the probe L were investigated by
systems. Among the different anions, the semi-ionic, three-center,
several metal ions, such as K+, Na+, Mg2+, Ca2+, Pb2+, Pd2+, Cd2+,
Hg2+, Zn2+, Cu2+, Al3+, Ag+, Fe2+, Co2+, Ni2+ and Mn2+ in
DMSO:H2O (8:2, v/v, 10 mM HEPES buffer, pH 7.4) solution at
room temperature. As illustrated in Fig. 2, the free probe L
-
and four-electron bonding bifluoride ions (HF2 ) recognition is of
5
growing interest because of its extensive applications in various
fields including etching of borosilicates glass capillary columns,
insecticides, fluorometric detection of ultra-trace levels of
beryllium in occupational hygiene samples, preparation of borane
45 displayed
a maximal absorption peak at 345 nm which
corresponds to π-π* transition from the conjugated moiety of L.
However, upon gradual addition of Al3+ ion to the solution of L,
9
derivatives and molten salts.23 Until now,
a very few
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10 chemosensors have been reported for bifluoride ions.24 Therefore,
it is an urgent requirement for fluorescent and biocompatible
probes that can selectively and sensitively detect bifluoride ions
with rapid response through easy spectral analysis. However, the
design and development of fluorescent chemosensors for anions
15 in aqueous solution is still a difficult task due to strong hydration
properties of anions. This problem could be evaded by using the
metal displacement strategy. Keeping this in mind, we report here
the initial absorption band at 345 nm decreased and
a
simultaneous increase at 402 nm with a red shift of 57 nm was
50 observed, accompanied by a naked eye color change from
colorless to light yellow. The clear isosbestic point at 370 nm
undoubtedly indicates the formation of Al3+ complex in the
binary mixture. Again, chemosensor L did not exhibit any
noteworthy changes in absorption spectra with the addition of a
55 number of competitive metal ions, signifying the high selectivity
of this probe for Al3+ ion. To investigate the suitable pH range in
which sensor, L can effectively detect Al3+, a pH titration of L
was carried out (Fig. S15, ESI†). It is noteworthy to mention that
addition of Al3+ resulted in a high absorbance in a pH range of 6
60 to 9. When pH is greater than 9, the absorbance is decreased due
to the formation of colloidal Al(OH)3.These observations indicate
that the pH range of 6 to 9 is suitable for monitoring Al3+ by the
chemosensor, L.
a
displacement-based sensing system by using Al3+-based
ensemble (L-2Al3+) for bifluoride ions recognition. It is
20 noteworthy to mention that the chemosensor L has interesting
analytical features like its easy synthetic route with good yield
and reasonably low detection limit for Al3+ ion with no
interference from a number of cations in comparison to reported
methods (Table S1, ESI†). Another notable aspect of L-2Al3+
25 complex is that it displays a good reversible fluorescence
-
response to HF2 . Furthermore, probe
L is effectively
applied to image Al3+ and HF2 ions in cultured HepG2
-
cells.
65
Results and discussion
30 Scheme 1 outlined the synthetic route of chemosensor L.
Compound 1 was prepared following literature procedure.25 The
probe L was then synthesized by the condensation reaction
between compound 1 and 2-hydroxy-4-chlorobenzaldehyde with
1
84% yield. The molecular structure of L was confirmed by H
Fig. 1 ORTEP view of molecular probe L (with 40% probability).
35 NMR, 13C NMR, ESI-MS, FT-IR and also by single-crystal X-ray
Al3+
(b)
(a)
70
diffraction analysis (Fig. 1, Table S2, ESI†).
L
N2H4, EtOH
SOCl2, MeOH
Reflux, 3 hr
Reflux, 4 hr
O
O
N
HOOC
N
COOH H3COOC
N
COOCH3
NH
HN
H2N
NH2
1
OH
O
N
O
N
CHO
N
75 Fig. 2 (a) The UV-vis absorption spectra of L (c = 2 × 10−4 M) in
presence of Al3+ (c = 2 × 10−5 M) ions in DMSO-H2O (8:2, v/v,
10 mM HEPES buffer, pH 7.4) solution. Inset: Color change after
addition of Al3+ to probe L. (b) Absorption spectra of L in
presence of different metal ions.
MeOH
Reflux, 5 hr
OH
1
+
NH
HN
OH
Cl
L
Cl
Cl
80 As shown in Fig. 3a, in absence of Al3+ ion, probe L showed a
very weak emission band centred at 483 nm (λext = 371 nm) in
DMSO-H2O (8:2, v/v, 10 mM HEPES buffer, pH 7.4). This weak
emission of probe L is due to the (a) excited state intramolecular
Scheme 1 Chemical structure and synthetic route of L.
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proton transfer (ESIPT) from the −OH group to the imine
nitrogen; (b) photoinduced electron transfer effect from the lone
pair of imine nitrogen and (c) isomerization of the −HC=N
(imine) bond.26 However, treatment of probe L with 3 equivalent
The result shows that the intensity of the proton signal
corresponding to the hydroxyl group (–OH) at 11.08 ppm, which
is the most probable binding site for Al3+ ions, decreases
significantly relative to that of other protons upon exposure to
5
Al3+ ions induced a gradual increase in fluorescence (20-fold) 50 Al3+ ions.
along with a blue shift of 7 nm having highest emission intensity
For the chemosensor L, IR spectrum (Fig. S4, ESI) shows ν(OH),
at 476 nm and a color change from dark to greenish-blue under
UV light. This significant fluorescence ‘turn-on’ in presence of
Al3+ ions might be explicated by the formation of a complex
3472(s); ν(NH), 3248(s); ν(C=O), 1657(s); ν(C=N), 1621 cm−1.
On the other hand, IR spectrum of L-Al3+complex (Fig. S6, ESI)
shows shifted frequency value and a new signal for NO3− at 1349
55 cm−1. The spectrum shows ν(NH), 3189(s); ν(C=O), 1672(s);
ν(C=N), 1617 cm−1 but the ν(OH) appears as broad signal at 3449
cm−1.This result shows that the −OH is the most probable binding
site for Al3+ ions.
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10 between the probe L and Al3+ through the coordination of two
“O” and one “N” atom. This inhibits both the ESIPT and PET
processes as well as C=N isomerization resulting in a distinctive
chelation enhanced fluorescence (CHEF) effect. In order to
explore the practical applicability, the pH effects on the
15 fluorescence response of probe L in absence and presence of Al3+
were examined. Fig. S16 shows that the L is weakly emissive in
the wide range of pH (3-13). The low emission intensity of L-
Al3+ complex at pH < 6 was presumably due to the free L that
remains uncoordinated to Al3+. At pH > 9, Al3+ is converted to
The Job’s plot revealed that 1:2 stoichiometry is the most
60 probable binding mode between L and Al3+ ions (Fig. S10, ESI†).
To attain such type of stoichiometry, imine nitrogen, carbonyl
oxygen and phenolic oxygen atoms are the most likely binding
sites for Al3+ ions (Scheme 2). The association constant (Ka) of L
for Al3+ was calculated from the Benesi–Hildebrand equation27 on
65 the basis of fluorometric titration as 4.26 × 104 M-1 (Fig. S12,
ESI†). The selectivity of chemosensor L towards different metal
cations were examined under identical working conditions. As
shown in Fig. 5, probe L demonstrated strong fluorescence
response at 476 nm, while the other cations [K+, Na+, Mg2+, Ca2+,
70 Pb2+, Pd2+, Cd2+, Hg2+, Zn2+, Cu2+, Ag+, Fe2+, Co2+, Ni2+ and
Mn2+] did not cause any remarkable emission spectral changes. In
order to further evaluate the practical capability of probe L as
Al3+ selective fluorescent chemosensor, we conducted
competitive experiments on addition of Al3+ ions to the solution
75 of L in presence of excess equivalent of other individual
competitive metal ions. The increase in fluorescence intensity
induced by mixing Al3+ ions with other miscellaneous cations
was comparable to that elicited by Al3+ alone, indicating stable
complexation between L and Al3+. The above results indicate
80 high selectivity of probe L for Al3+ over other commonly
coexistent cations in organo-aqueous solution. The fluorescence
intensity of the L at 476 nm exhibited a good linear relationship
with the Al3+ concentration ranging from 0.99 µM to 20.6 µM,
based on which the detection limit 28 for Al3+ was calculated to be
85 0.8µM (Fig. S11, ESI†).
-
20 Al(OH)3 and Al(OH)4 , leaving the sensor almost in its free
anionic form in the solution. At pH ~ 7 the sensor is deprotonated
and the resulting dianionic ligand forms a chelate with Al3+,
leading to the fluorescence enhancement via CHEF mechanism
(Scheme 2). Therefore, L sensor is capable of being used for
25 selective detection of Al3+ at physiological pH, and can be a
suitable candidate for biological applications.
30
Fig. 3 Changes in fluorescence spectra of L (c = 2 × 10-4 M) in
presence of different amount of Al3+ (c = 2 × 10-5 M) ions in
DMSO-H2O (8:2, v/v, 10 mM HEPES buffer, pH 7.4) solution.
35 Inset: Fluorescence change after addition of Al3+ to probe L.
Additionally, 1H NMR titration was performed by gradual
addition of nitrate salt of Al3+ ions to a DMSO-d6 solution of L
(Fig. 4).
40
90
Fig. 5 Fluorescence response of L (c = 2 × 10−4 M) to different
metal ions in DMSO-H2O (8:2, v/v, 10 mM HEPES buffer, pH
7.4) solution (λext = 370 nm).
Fig. 4 1HNMR spectra in DMSO-d6: (a) L only (b) L and 1 equiv.
45 of Al3+(c) L and 2 equiv. of Al3+.
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Reversibility is an essential feature of a probe to be used as a
chemosensor to detect particular metal cations. Here, the in situ
generated L-2Al3+ complex displayed fluorescence “turn-off”
behavior only in presence of HF2- ion. Now, to inspect this, when
an excess amount of NaHF2 solution was added to the solution
containing L-2Al3+ complex system, the emission band at 476 nm
was gradually decreased, accompanied by the emission color
changes from deep blue to dark (Fig. 6a). However, various
5
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−
−
common anions such as Cl−, Br−, AcO−, CO32−, N3 , HCO3 ,
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10 NO2 , SO42−, H2PO4 did not produce any noticeable results
under the similar conditions except F-. F- ion decreases the
fluorescence intensity but only by a small extent compared to
−
−
Scheme 2 Proposed sensing mechanism for detection of Al3+ by
probe L.
-
HF2 ion (Fig. 6b). The added fluoride source (TBAF) could be
hydrolyzed, and a small amount of HF2- may be generated in situ
15 to assist the quenching of emission of L-2Al3+ complex; thus, a
quenching response might be observed.29 Such fluorometric
changes was mainly due to the removal of Al3+ from L-2Al3+
system followed by the regeneration of probe L as shown in
Scheme 2. These properties indicate that L-2Al3+ ensemble is
20 employed as an “on-off” fluorescent sensor for bifluoride ion. In
addition, the reversible and reusable behavior of probe L was also
verified by performing four alternate cycles of fluorescence
titration of L with Al3+ followed by addition of HF2- as shown in
Fig. S7 (ESI†). Moreover, from the fluorescence titration
25 experiment, we found a good linear relationship of fluorescence
intensity versus the HF2- concentration over a range of 0.99 to 6.5
µM (Fig. S8, ESI†).
In order to know the optimized geometry of L and L-2Al3+ and
50 the binding interactions between probe L and Al3+, we carried out
density functional theory (DFT) calculations with the B3LYP/6-
311+G(d,p) basis set using the Gaussian 16 program.30,31 The
energy optimized structures of L and Al-complex were presented
in Fig. 7. The highest occupied molecular orbital (HOMO),
55 lowest unoccupied molecular orbital (LUMO) energies and
spatial distribution of L and L-2Al3+ were also calculated (ESI†).
As shown in Fig. 8, the HOMO-LUMO energy gap of probe L
was considerably reduced from 3.83 eV (88.4 kcal/mol) to 3.16
eV (72.9 kcal/mol) in the L-2Al3+ complex, establishing that L
60 formed stable complex with Al3+ ion and supports the red-shifting
of the absorption band (λmax) in the UV-Vis absorption spectra.32
Moreover TDDFT calculation were performed on the optimized
geometries to explain the electronic properties of probe L and its
Al-complex. Table S4 showed the details of the vertical
65 excitation energies, oscillator frequencies and wavelengths and
from these data it was found that the computed vertical transitions
were analogous with the experimentally observed UV−vis bands.
However, incremental addition of HF2- ion into the solution of in
30 situ generated L-2Al3+ complex led to a gradual decrease in
absorption band at 394 nm and a concomitant increase in the
intensity of a new absorption band centered at 344 nm (Fig. S9,
ESI†).
The probe was applied in Hep G2 cells (Human liver cancer cell
line) for fluorescence imaging of intracellular Al3+ ions to
70 investigate its application in biological system. First, Hep G2
cells were treated with probe L (10 µM) for 30 min at 37°C and
35
(a)
75
40 Fig. 6 (a) Fluorescence titrations of L-2Al3+ complex with
sodium salt of bifluoride in DMSO-H2O (8:2, v/v, 10 mM
HEPES buffer, pH 7.4) solution (λext = 370 nm). Inset:
(b)
-
Fluorescence photographs of L+Al3+ and L+Al3++HF2 . (b)
80
Changes in the fluorescence spectra of L-2Al3+ complex in
45 presence of different anions.
85
Fig. 7 The calculated energy minimized structures of L and L-
2Al3+ complex.
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Conclusions:
In conclusion, we have successfully designed and synthesized a
55 colorimetric and fluorometric probe, L, based on pyridine-
dicarbohydrazide. The probe L shows both color and switch-on
emission response to Al3+ ions in organo aqueous solution as a
result of metal enhanced chelation effect (CHEF) inhibiting the
PET, ESIPT and C=N isomerization processes. With a detection
60 limit of 0.8µM, this chemosensor displays high selectivity for
Al3+ ions over other 18 commonly coexistent metal ions. The
stoichiometry of the L-Al3+ is determined to be 1:2 (L: Al3+) and
is confirmed by Job’s plot analysis. The association constant for
L with Al3+ is found to be 4.26 × 104 M-1 on the basis of
65 fluorescence studies, proposing a strong binding affinity for Al3+.
Besides, the in situ prepared L-2Al3+ complex can be utilized for
LUMO
5
5
LUMO
6
7
8
9
88.4 kcal/mol
72.9 kcal/mol
10
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15
HOMO
HOMO
L-2Al3+
L
15 Fig. 8 HOMO and LUMO distributions of L and L-2Al3+
-
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the detection of HF2 ions via the displacement approach and it
complex.
exhibits a “turn-off” type of fluorescence response. Moreover, the
-
detection of Al3+ and HF2 ions was also carried out in HepG2
then washed with PBS buffer to remove excess probe. After that,
the treated cells were incubated with Al3+ ions (10 µM) for
20 another 30 min at 37°C. Then, these incubated cells were washed
again with PBS buffer and images were recorded using a
fluorescence microscope. Hep G2 cells treated with only probe L
displayed no fluorescence signal, whereas an intense green
fluorescence signal was detected in the intracellular area when
25 stained with L followed by Al(NO3)3. Again, this bright
fluorescence signal disappeared when the cells were treated with
NaHF2 (10 µM) solution (Fig. 9). Furthermore, there were no
gross morphological changes in bright-field images of cells,
suggesting that the cells remained viable throughout the imaging
30 studies. The above results established the good cell-membrane
permeability of L and that it could be employed in living cells for
70 cells to demonstrate the “off-on-off” fluorescence cellular image.
It proves that molecule penetrates to cell and thus it is applicable
to biological system. We anticipate that such type of cell imaging
-
studies will be useful for Al3+ and HF2 ions related biological
studies.
75 Experimental Section
Materials and apparatus:
All the chemical reagents and solvents (analytical and
spectroscopic grades) were procured from commercial suppliers
and used without additional purification. Millipore water was
80 used throughout the experiment. Nitrate salts of Al3+and Ag+,
chloride salts of metal ions (Na+, K+, Cr3+, Cd2+, Fe2+, Zn2+, Hg2+,
Pb2+) and perchlorate salts of metal ions (Ni2+, Mn2+, Cu2+, Fe2+,
−
in vitro imaging of Al3+ and HF2 ions. Additionally, an MTT
assay determined that probe L displayed very low cytotoxicity
toward living cells (Fig. S14, ESI†).
−
Co2+), terabutyl ammonium salts of F−, Br−, AcO−, HSO4 and
−
−
sodium salts of HF2 , PPi, Pi, NO3 were used for the
85 experiments. Elemental analyses (C, H and N) were performed
35
Fluorescence
Bright Field
Overlay
using
a PerkinElmer 2400 Series-II CHN analyzer, USA
c
a
b
e
elemental analyzer. ESI mass spectra were obtained from a Water
HRMS model XEVO-G2QTOF#YCA351 spectrometer. 1H NMR
and 13C NMR spectra were obtained from Bruker spectrometer
90 (400 MHz) and 1H NMR titration spectra were obtained from
Bruker spectrometer (300 MHz) with DMSO-d6 solvent using
trimethylsilane (TMS) as an internal standard. Fourier transform
infrared (FT-IR) spectra were recorded on a Perkin Elmer LX-1
FT-IR spectrophotometer (4000−400 cm−1) by using a modern
95 diamond attenuated total reflectance (ATR) accessory. UV−vis
absorption spectra were obtained using UV-1700 PharmaSpec
UV−vis spectrophotometer (SHIMADZU). Fluorescence
emission spectra were carried out using a Horiba Jobin Yvon
Fluoromax-4P spectrofluorometer. Single crystal structures (Fig.
100 1) were obtained using single-crystal X-ray diffractometer
(Bruker Smart Apex II). The cells were imaged by using
Zetasizer fluorescence microscope (Leica).
40
f
i
d
g
45
h
Fig. 9 Bright field, fluorescence and overlay images of Hep G2
50 cells. (a-c) cells were incubated with 10 μM probe L for 30 min,
(d-f) followed by addition and incubation with 10 μM Al3+ for
another 30 min and (g-i) then with NaHF2 for 30 min.
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Calculations for detection limit:
Synthesis
Pyridinedicarbohydrazone (L):
of
Bis(2-hydroxy-4-chlorobenzaldehyde)-2,6-
The detection limit of L for Al3+ was calculated using the
following equation28:
2,6-pyridinedicarbohydrazide was synthesized following reported
50 method (Scheme 1).25 A mixture of 2,6-pyridinedicarbohydrazide
(0.19 g, 1.0 mmol) and 2-hydroxy-4-chlorobenzaldehyde (0.36 g,
2.3 mmol) was refluxed in methanol for 5 h. A light yellow solid
formed was filtered off and dried in vacuum (yield 0.39 g (84%).
m.p. > 200°C). Anal. Calc. for C21H15Cl2N5O4, C 53.41, H 3.20,
Detection limit = 3Sb1/S
(1)
5
Where Sb1 is the standard deviation of the blank solution; and S
is the slope of the calibration curve.
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1
55 N 14.83. Found: C 54.12, H 4.01, N 15.23 %. H NMR (400
Theoretical calculation:
MHz, DMSO-d6 ): δ = 12.47 (s, 2H), 11.09 (s, 2H), 8.88 (s, 2H),
8.35 (d, J = 7.2 Hz, 2H), 8.28 (m, 1H), 7.92 (s, 3H), 7.75 (d, J =
2.4 Hz, 2H), 7.34 (m, 6.8 Hz, 2H), 6.97 (d, J = 8.8 Hz, 2H). 13C
NMR (100 MHz, DMSO-d6): δ = 207.02 (for C=O of DMF),
60 162.79, 160.01, 156.46, 148.43, 147.17, 140.52, 131.64, 127.39,
126.22, 123.67, 121.48, 118.76, 31.17. IR (KBr, cm-1): 3472,
3248, 1657, 1621, 1538, 1481, 1353, 1264, 1187, 1089, 1000,
950, 824, 716, 608, 560. ESI-MS: m/z 472.11, calcd for
[C21H15Cl2N5O4 + H]+ 472.06. Crystals suitable for X-ray
65 structural determination were obtained by slow evaporation of
DMF solution.
All the geometries for L and L-2Al3+ were optimized by density
functional theory (DFT) calculations using Gaussian 16 software
10 package (basis set: B3LYP/6-31+G(d,p)). TDDFT calculation
was also performed in the same level of theory.
Cell imaging studies
Cell line culture
Human liver cancer cell line Hep G2 cells and Human lung
15 fibroblast cells, WI-38 were collected from National Center for
Cell Science (NCCS) Pune, India. The cells were grown in
DMEM (Dulbecco's Modified Eagle Medium) with 10% FBS
(Fetal Bovine Serum), penicillin/streptomycin (100units/ml) at
Acknowledgements
Samit Pramanik thanks Council of Scientific and Industrial
37ºC and 5% CO2. All the treatments were performed at 37ºC and 70 Research (CSIR, File no. 09/096(0947)/2018-EMR-I), New
20 at a cell density allowing exponential growth.
Delhi, for Junior Research Fellowship. The authors are thankful
to Prof. Nitin Chattopadhyay and his scholar Mr. Sinjan Das of
Department of Chemistry, Jadavpur University for instrumental
facility. SKM and SP thank Haldia Government College for
75 partial laboratory facility. DM is very much thankful to the DST,
Government of India, for providing the INSPIRE Faculty
Fellowship (DST/INSPIRE/04/2016/001948).
Cell survivability assay
Cell survivability of the ligand were studied for human lung
fibroblast cells, WI38 following reported procedure.33 In brief,
viability of WI-38 cells after exposure to various concentrations
25 of probe L were assessed by MTT assay. The cells were seeded
in 96-well plates at 1 × 104 cells per well and exposed to probe L
at concentrations of 0 µM, 20 µM, 40 µM, 60 µM, 80 µM, 100
µM for 24 hrs. After incubation cells were washed with 1×PBS
twice and incubated with MTT solution (450µg/ml) for 3-4 hrs at
30 37ºC. The resulting formazan crystals were dissolved in an MTT
solubilization buffer and the absorbance was measured at 570 nm
by using a spectrophotometer (BioTek) and the value was
compared with control cells.
Notes and references
aDepartment of Chemistry, Jadavpur University, Kolkata 700032,
80 India
bDepartment of Chemistry, Haldia Government College, Debhog,
Purba Medinipur, West Bengal, India
cSchool of Chemistry and Biochemistry, Thapar Institute of
Engineering and Technology, Patiala 147004, Punjab, India
85 dDepartment of Life Science and Biotechnology, Jadavpur
University, Kolkata 700032, India
Cellular Imaging
*Sudipta Pathak, Tel: +91-8001317336.
E-mails:sudiptachemster@gmail.com
†Electronic Supplementary Information (ESI) available: CCDC
90 1979155 [details of any supplementary information available
should be included here]. See DOI: 10.1039/b000000x/
35 According to reported procedure, the Hep G2 cells were grown in
a coverslip for more than 24h. Then, the Hep G2 cells were
treated with 10µM of probe L for 30 min followed by addition
and incubation with 10µM Al(NO3)3 solution and then with
NaHF2 solution. The cells were washed with 1 X PBS. Lastly,
40 they were then mounted on a glass slide and fluorescent images
were taken from the Leica fluorescence microscope.
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Chromogenic and fluorogenic “off-on-off” chemosensor for selective and
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sensitive detection of aluminum (Al3+) and bifluoride (HF2 ) ions in solution
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and in living HepG2 cells: synthesis, experimental and theoretical studies
Samit Pramanik,a Saikat Kumar Manna,b Sudipta Pathak,b,* Debasish Mondal,c Kunal Pal,d and
Subrata Mukhopadhyay a
aDepartment of Chemistry, Jadavpur University, Jadavpur, Kolkata, West Bengal, India
bDepartment of Chemistry, Haldia Government College, Debhog, Purba Medinipur, West
Bengal, India
cSchool of Chemistry and Biochemistry, Thapar Institute of Engineering and Technology,
Patiala - 147004, Punjab, India
dDepartment of Life Science and Biotechnology, Jadavpur University, Kolkata 700032, India