- Email: [email protected]
Fluorescent sensor for copper(II) ions based on coumarin derivative and its application in cell imaging
Inorganic Chemistry Communications 102 (2019) 51–56
Contents lists available at ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
Short communication
Fluorescent sensor for copper(II) ions based on coumarin derivative and its application in cell imaging
T
Sheng Fenga, Qianmiao Gaob, Xu Gaob, Jiqiu Yinb,c, , Yang Jiaob ⁎
a
School of Environmental and Safety Engineering, Changzhou University, Jiangsu 213164, China College of Chemistry, Dalian University of Technology, Dalian 116024, China c College of Medical Laboratory, Dalian Medical University, Dalian 116044, China b
GRAPHICAL ABSTRACT
The sensor CHT based on coumarin derivatives could recognize Cu2 + ions with high sensitivity and selectivity in the presence of other important relevant metal ions, and it has potential applications in cell imaging.
ARTICLE INFO
ABSTRACT
Keywords: Coumarin Copper(II) ions Fluorescent sensor Cell imaging
A novel fluorescent sensor CHT based on the excellent optical properties of coumarin derivatives was designed. It was synthesized by Schiff base reaction connected by 7-(N,N-diethylamino) coumarin-3-aldehyde and 2-hydrazinobenzothiazole. The sensor CHT exhibited a significant fluorescence quenching at 540 nm upon the addition of Cu2+ ions. And the sensor exhibited good sensitivity, fast response time, high selectivity for Cu2 + ions in the presence of other important relevant metal ions. In addition, fluorescent sensor CHT was successfully applied for fluorescent imaging of Cu2+ ions in A549 and MCF-7 cells, demonstrating its potential applications in live cell imaging.
Copper, a vital trace metal element, is regarded as one of the most abundant metal ions in biological systems, which play an important role in various physiological processes such as signal transduction, participating in redox reactions, affecting the central nervous system, energy generation. At the same time, copper is a metal used in architecture, household items and manufacturing. In human body, Cu2+ ions are a cofactor of many enzymes and related to a variety of physiological
⁎
processes including bone formation and growth, crosslinks formation in collagen and connective tissue maintain and repair [1–6]. Although Cu2+ ions are important for industry, agriculture and humans, the accumulation of excessive Cu2+ ions could cause environmental pollution, liver and kidneys damage, and a series of neurodegenerative diseases such as Parkinson's disease, prion disease and Wilson disease [7–9]. Therefore, it is of great significance to recognize Cu2+ ions in the
Corresponding author at: College of Chemistry, Dalian University of Technology, Dalian 116024, China. E-mail address: [email protected] (J. Yin).
https://doi.org/10.1016/j.inoche.2019.01.012 Received 7 October 2018; Received in revised form 29 December 2018; Accepted 10 January 2019 Available online 11 January 2019 1387-7003/ © 2019 Published by Elsevier B.V.
Inorganic Chemistry Communications 102 (2019) 51–56
S. Feng et al.
Scheme 1. Syntheses procedure of sensor CHT.
with excellent properties, coumarin and its derivatives have been widely researched and many researchers have been performed on design of fluorescence sensors based small molecule dye for recognition of Cu2+ ions. Coumarin derivatives have perfect photochemical properties, photo-physical properties, biocompatibility, as well as good versatility when they used as buiding blocks in organic synthesis [27–32]. Several coumarin derivatives sensors have been reported due to their short response time [33–37], high selectivity and sensitivity [38–42]. The kind of fluorescence sensor are easy to be embedded within cells and tissues for fluorescent imaging of Cu2+ ions, which extends its application in bioimaging and in the commerical use. Herein a new fluorescent sensor CHT for recognition of Cu2+ ions was designed, which synthesized by Schiff base reaction could selectively recognize Cu2+ ions in acetonitrile and PBS buffer media. Based on excellent photo-physical properties of coumarin derivative, 7-(N,Ndiethylamino) coumarin-3-aldehyde was applied to connect 2-benzothiazolinonehydrazone using C]N as bridge. The sensor CHT displayed fluorescenc response for the selective recognition of Cu2+ ions in the presence of other commonly interfered metal ions. The sensor CHT has good biocompatibility, and it could achieve imaging in A549 cells and MCF-7 cells. The sensor CHT was connected by 7-(N,N-diethylamino) coumarin3-aldehyde and 2-hydrazinobenzothiazole with three steps. The detailed synthesis procedure and chemical structure of sensor CHT are illustrated in Scheme 1, and the structure of sensor CHT was well characterized by 1H NMR, 13C NMR and ESI-MS (Figs. S1–S9). The UV–vis absorption spectra were investigated in acetonitrile and PBS buffer solution (pH = 7.4). The absorption spectrum of sensor CHT displayed a strong band with a maximum absorbance peak at 500 nm as shown in Fig. 1. After addition of Cu2+ ions to solution, the absorption peak at 500 nm decreased. The absorption titration curve reached a plateau after added 5 equiv of Cu2+ ions. The fluorescent properties of sensor CHT were initially examined in the acetonitrile and PBS solution. The fluorescent spectra of sensor CHT (2 μM) were recorded at excitation wavelength of 450 nm to observe its fluorescence intensity response to Cu2+ ions. As shown in Fig. 2, at the excitation wavelength of 450 nm, the sensor CHT showed a strong fluorescent emission at 540 nm. The emission intensity was quenched upon gradual addition of Cu2+ ions. The interaction between sensor and Cu2+ ions was extra fast and the fluorescence intensity showed a significant decrease after adding 0.5 equiv of Cu2+ ions. The fluorescence intensity titration curve would reach a plateau after adding 5 equiv Cu2+ ions. The mass spectrum showed an intense peak with m/z = 393.13 in acetonitrile and it could be assigned to [CHT + H]+ referring to the exact comparison of the peak with the simulation on the basis of natural isotopic abundances. As shown in Fig. 3, the intense peak at m/ z = 454.05 was corresponding to [CHT + Cu2+-H]+, which were identical to calculated peaks upon addition of Cu2+ ions. This result derived from the interaction between copper ions and sensor CHT. These results clearly indicate the formation of the complex with 1:1 stoichiometric binding between sensor CHT and Cu2+ ions. To identify the good photostability and quick response of sensor CHT, the time-dependent fluorescence experiment was designed. Sensor CHT was added into acetonitrile and PBS solution and the
Fig. 1. UV–Vis spectra of sensor CHT (20 μM) with addition of various concentrations of Cu2+ ions in acetonitrile/PBS (1:1, v/v, pH = 7.4).
Fig. 2. Fluorescence spectra of sensor CHT (2 μM) with addition of various concentrations of Cu2+ ions (0–10 μM) in acetonitrile/PBS (1:1, v/v, pH = 7.4) with an excitation at 450 nm.
biological and environment systems [10–15]. In the past few decades, several methods for recognition of Cu2+ ions in biological and enviromental samples have been proposed which include electrochemical methods, mass spectrometry (MS), atomic absorption spectroscopy (AAS), atomic emission spectroscopy (AES), inductively coupled plasma (ICP), voltammetry and fluorometry, etc. Among the variety of methods for Cu2+ ions recognition, fluorescent techniques have attracted more attention due to their evident advantages such as non-destructive nature, real-time detection, high sensitivity and selectivity and so on [16–26]. As a class of dye molecules 52
Inorganic Chemistry Communications 102 (2019) 51–56
S. Feng et al.
Fig. 3. ESI-MS of sensor CHT in the presence 1 equivalents molar ration of Cu2+ ions in acetonitrile. Insert: the experimental and theoretical MS peak of complex sensor CHT and Cu2+.
free sensor in acetonitrile/PBS buffer (1:1, v/v, pH = 7.4). However, the fluorescence intensity decreased immediately and reached the maximum within 4 min upon the addition of 5 equiv Cu2+ ions. The fast response feature of the sensor CHT is particularly important for the practical real-time detection. The recognition of Cu2+ ions by the sensor CHT might be effect by other metal ions in physiological environment. The fluorescent response of potential interferential metal ions was investigated. The 5 equiv other metal ions (Mg2+, Zn2+, K+, Na+, Fe3+, Mn2+, Co2+, Ni2+, Ag+, Cd2+, Pb2+, Ca2+, Hg2+) did not cause obvious changes to the fluorescent emission at 540 nm, but when Cu2+ ions were added, the fluorescence quenched markedly, as shown in Fig. 5. All these experimental results showed that the sensor CHT is only quenched by Cu2+ ions. It demonstrated that sensor CHT could selective recognize Cu2+ ions from other interference ions and the presence of other relevant metal ions could not influence the recognition of Cu2+ ions. CCK8 assay was performed to determine the cytotoxicity of the sensor CHT. Cells were seeded in 96 well plates for 24 h and different concentrations (0, 1, 2, 5, 10 and 20 μM) of sensor CHT were added to the cell culture medium incubated for 24 h. The cell relative growth rate was determined by CCK8 assay, the absorbance with an enzyme marker was determined. The results indicate in Fig. 6 that at concentrations below 20 μM, sensor CHT has a low cytotoxicity to A549 cells and MCF-7 cells and it shows the sensor could be applied in vivo. To evaluate the sensor CHT application in real water systems, the study on the recovery of copper(II) ions was carried out in tap water with different amounts of Cu2+ ions. Different concentrations of Cu2+ ions were spiked in water sample, and Table 1 indicates an acceptable recovery and relative standard deviation (RSD). The recovery of Cu2+ ions at each concentration for the water samples was statistically close
Fig. 4. Time-dependent fluorescence response of sensor CHT (black line) and sensor CHT with the addition 5eqiv Cu2+ ions (red line) in aqueous acetonitrile (1:1, v/v). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
fluorescence signals of sensor CHT was apparent stability within 40mins. In the same conditions, sensor CHT was added into acetonitrile and PBS solution and then 5 equiv Cu2+ ions were added into solution. As shown in Fig. 4, a stable fluorescence signal was observed with the
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S. Feng et al.
Fig. 5. (a) Fluorescence response of the probe (2 μM) in the presence of various relevant cations (10 μM) that are abundant in cells in acetonitrile/PBS buffer (1:1, v/v, pH = 7.4). (b) The dungaree bars represent the emission intensities of sensor CHT in the presence of 10 μM other common cations respectively. The wine bars represent the change in emission upon subsequent addition of 10 μM of Cu2+ to the above solution with an excitation at 450 nm and emission at 540 nm.
Fig. 6. Relative growth rate (%) was estimated by the CCK8 assay. (a) The sensor CHT was cultured in the A549 cells for 24 h. (b) The sensor CHT was cultured in the MCF-7 cells for 24 h.
Table 1 Results of the recognition of Cu2+ in actual water samples.
to 100% (range from 92.90% to 109.03%), showing future practical applicability of probe for Cu2+ ions recognition in real samples analysis. The ability of sensor CHT to track Cu2+ ions in living cells was measured through confocal microscopy. The A549 cells and MCF-7 cells were incubated with 1 μM sensor CHT for 20 min, and then added varied concentration of Cu2+ ions (0, 0.5, 1 and 2 μM) for another 20 min. The cells were washed three times with PBS buffer before imaging with confocal laser scanning microscopy. The cells exhibited strong fluorescence when induced by excitation light source of 458 nm, and cells treated with Cu2+ ions (2 μM) showed fluorescence quenching (Fig. 7). The confocal microscopy images strongly suggested that fluorescent sensor CHT was successfully applied for fluorescent imaging of Cu2+ in living cells. In conclusion, a novel fluorescent sensor CHT has been designed and synthesized, which based on a schiff base condensation of 7-(N,N-
Spiked (μM) 1 2 3
Found (μM)
Recovery (100%)
RSD (%) (n = 3)
1.0926 1.9361 2.7869
109.3 96.80 92.90
2.00 1.17 0.87
diethylamino) coumarin-3-aldehyde and 2-hydrazinobenzothiazole. As a fluorescent sensor, CHT exhibited a significant fluorescence quenching at 540 nm upon the addition of Cu2+ ions. In the presence of other important relevant metal ions in acetonitrile/PBS buffer (1:1, v/v, pH = 7.4), sensor CHT exhibited high selectivity towards Cu2+ ions. The sensor CHT could recognize Cu2+ ions under physiological pH conditions and has been successfully utilized for fluorescence imaging of Cu2+ ions in biological system.
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Fig. 7. Confocal microscpy images of cells incubated with sensor CHT and Cu2+. (a1, a2, a3, a4) Fluorescent images of sensor CHT (1 μM) treated A549 cells and incubated with Cu2+ (0 μM, 0.5 μM, 1 μM, 2 μM) respectively. (b1, b2, b3, b4) Fluorescent images of sensor CHT (1 μM) treated MCF-7 cells and incubated with Cu2+ (0 μM, 0.5 μM, 1 μM, 2 μM) respectively. Excitation was at 458 nm.
Acknowledgments
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56
Contents lists available at ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
Short communication
Fluorescent sensor for copper(II) ions based on coumarin derivative and its application in cell imaging
T
Sheng Fenga, Qianmiao Gaob, Xu Gaob, Jiqiu Yinb,c, , Yang Jiaob ⁎
a
School of Environmental and Safety Engineering, Changzhou University, Jiangsu 213164, China College of Chemistry, Dalian University of Technology, Dalian 116024, China c College of Medical Laboratory, Dalian Medical University, Dalian 116044, China b
GRAPHICAL ABSTRACT
The sensor CHT based on coumarin derivatives could recognize Cu2 + ions with high sensitivity and selectivity in the presence of other important relevant metal ions, and it has potential applications in cell imaging.
ARTICLE INFO
ABSTRACT
Keywords: Coumarin Copper(II) ions Fluorescent sensor Cell imaging
A novel fluorescent sensor CHT based on the excellent optical properties of coumarin derivatives was designed. It was synthesized by Schiff base reaction connected by 7-(N,N-diethylamino) coumarin-3-aldehyde and 2-hydrazinobenzothiazole. The sensor CHT exhibited a significant fluorescence quenching at 540 nm upon the addition of Cu2+ ions. And the sensor exhibited good sensitivity, fast response time, high selectivity for Cu2 + ions in the presence of other important relevant metal ions. In addition, fluorescent sensor CHT was successfully applied for fluorescent imaging of Cu2+ ions in A549 and MCF-7 cells, demonstrating its potential applications in live cell imaging.
Copper, a vital trace metal element, is regarded as one of the most abundant metal ions in biological systems, which play an important role in various physiological processes such as signal transduction, participating in redox reactions, affecting the central nervous system, energy generation. At the same time, copper is a metal used in architecture, household items and manufacturing. In human body, Cu2+ ions are a cofactor of many enzymes and related to a variety of physiological
⁎
processes including bone formation and growth, crosslinks formation in collagen and connective tissue maintain and repair [1–6]. Although Cu2+ ions are important for industry, agriculture and humans, the accumulation of excessive Cu2+ ions could cause environmental pollution, liver and kidneys damage, and a series of neurodegenerative diseases such as Parkinson's disease, prion disease and Wilson disease [7–9]. Therefore, it is of great significance to recognize Cu2+ ions in the
Corresponding author at: College of Chemistry, Dalian University of Technology, Dalian 116024, China. E-mail address: [email protected] (J. Yin).
https://doi.org/10.1016/j.inoche.2019.01.012 Received 7 October 2018; Received in revised form 29 December 2018; Accepted 10 January 2019 Available online 11 January 2019 1387-7003/ © 2019 Published by Elsevier B.V.
Inorganic Chemistry Communications 102 (2019) 51–56
S. Feng et al.
Scheme 1. Syntheses procedure of sensor CHT.
with excellent properties, coumarin and its derivatives have been widely researched and many researchers have been performed on design of fluorescence sensors based small molecule dye for recognition of Cu2+ ions. Coumarin derivatives have perfect photochemical properties, photo-physical properties, biocompatibility, as well as good versatility when they used as buiding blocks in organic synthesis [27–32]. Several coumarin derivatives sensors have been reported due to their short response time [33–37], high selectivity and sensitivity [38–42]. The kind of fluorescence sensor are easy to be embedded within cells and tissues for fluorescent imaging of Cu2+ ions, which extends its application in bioimaging and in the commerical use. Herein a new fluorescent sensor CHT for recognition of Cu2+ ions was designed, which synthesized by Schiff base reaction could selectively recognize Cu2+ ions in acetonitrile and PBS buffer media. Based on excellent photo-physical properties of coumarin derivative, 7-(N,Ndiethylamino) coumarin-3-aldehyde was applied to connect 2-benzothiazolinonehydrazone using C]N as bridge. The sensor CHT displayed fluorescenc response for the selective recognition of Cu2+ ions in the presence of other commonly interfered metal ions. The sensor CHT has good biocompatibility, and it could achieve imaging in A549 cells and MCF-7 cells. The sensor CHT was connected by 7-(N,N-diethylamino) coumarin3-aldehyde and 2-hydrazinobenzothiazole with three steps. The detailed synthesis procedure and chemical structure of sensor CHT are illustrated in Scheme 1, and the structure of sensor CHT was well characterized by 1H NMR, 13C NMR and ESI-MS (Figs. S1–S9). The UV–vis absorption spectra were investigated in acetonitrile and PBS buffer solution (pH = 7.4). The absorption spectrum of sensor CHT displayed a strong band with a maximum absorbance peak at 500 nm as shown in Fig. 1. After addition of Cu2+ ions to solution, the absorption peak at 500 nm decreased. The absorption titration curve reached a plateau after added 5 equiv of Cu2+ ions. The fluorescent properties of sensor CHT were initially examined in the acetonitrile and PBS solution. The fluorescent spectra of sensor CHT (2 μM) were recorded at excitation wavelength of 450 nm to observe its fluorescence intensity response to Cu2+ ions. As shown in Fig. 2, at the excitation wavelength of 450 nm, the sensor CHT showed a strong fluorescent emission at 540 nm. The emission intensity was quenched upon gradual addition of Cu2+ ions. The interaction between sensor and Cu2+ ions was extra fast and the fluorescence intensity showed a significant decrease after adding 0.5 equiv of Cu2+ ions. The fluorescence intensity titration curve would reach a plateau after adding 5 equiv Cu2+ ions. The mass spectrum showed an intense peak with m/z = 393.13 in acetonitrile and it could be assigned to [CHT + H]+ referring to the exact comparison of the peak with the simulation on the basis of natural isotopic abundances. As shown in Fig. 3, the intense peak at m/ z = 454.05 was corresponding to [CHT + Cu2+-H]+, which were identical to calculated peaks upon addition of Cu2+ ions. This result derived from the interaction between copper ions and sensor CHT. These results clearly indicate the formation of the complex with 1:1 stoichiometric binding between sensor CHT and Cu2+ ions. To identify the good photostability and quick response of sensor CHT, the time-dependent fluorescence experiment was designed. Sensor CHT was added into acetonitrile and PBS solution and the
Fig. 1. UV–Vis spectra of sensor CHT (20 μM) with addition of various concentrations of Cu2+ ions in acetonitrile/PBS (1:1, v/v, pH = 7.4).
Fig. 2. Fluorescence spectra of sensor CHT (2 μM) with addition of various concentrations of Cu2+ ions (0–10 μM) in acetonitrile/PBS (1:1, v/v, pH = 7.4) with an excitation at 450 nm.
biological and environment systems [10–15]. In the past few decades, several methods for recognition of Cu2+ ions in biological and enviromental samples have been proposed which include electrochemical methods, mass spectrometry (MS), atomic absorption spectroscopy (AAS), atomic emission spectroscopy (AES), inductively coupled plasma (ICP), voltammetry and fluorometry, etc. Among the variety of methods for Cu2+ ions recognition, fluorescent techniques have attracted more attention due to their evident advantages such as non-destructive nature, real-time detection, high sensitivity and selectivity and so on [16–26]. As a class of dye molecules 52
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Fig. 3. ESI-MS of sensor CHT in the presence 1 equivalents molar ration of Cu2+ ions in acetonitrile. Insert: the experimental and theoretical MS peak of complex sensor CHT and Cu2+.
free sensor in acetonitrile/PBS buffer (1:1, v/v, pH = 7.4). However, the fluorescence intensity decreased immediately and reached the maximum within 4 min upon the addition of 5 equiv Cu2+ ions. The fast response feature of the sensor CHT is particularly important for the practical real-time detection. The recognition of Cu2+ ions by the sensor CHT might be effect by other metal ions in physiological environment. The fluorescent response of potential interferential metal ions was investigated. The 5 equiv other metal ions (Mg2+, Zn2+, K+, Na+, Fe3+, Mn2+, Co2+, Ni2+, Ag+, Cd2+, Pb2+, Ca2+, Hg2+) did not cause obvious changes to the fluorescent emission at 540 nm, but when Cu2+ ions were added, the fluorescence quenched markedly, as shown in Fig. 5. All these experimental results showed that the sensor CHT is only quenched by Cu2+ ions. It demonstrated that sensor CHT could selective recognize Cu2+ ions from other interference ions and the presence of other relevant metal ions could not influence the recognition of Cu2+ ions. CCK8 assay was performed to determine the cytotoxicity of the sensor CHT. Cells were seeded in 96 well plates for 24 h and different concentrations (0, 1, 2, 5, 10 and 20 μM) of sensor CHT were added to the cell culture medium incubated for 24 h. The cell relative growth rate was determined by CCK8 assay, the absorbance with an enzyme marker was determined. The results indicate in Fig. 6 that at concentrations below 20 μM, sensor CHT has a low cytotoxicity to A549 cells and MCF-7 cells and it shows the sensor could be applied in vivo. To evaluate the sensor CHT application in real water systems, the study on the recovery of copper(II) ions was carried out in tap water with different amounts of Cu2+ ions. Different concentrations of Cu2+ ions were spiked in water sample, and Table 1 indicates an acceptable recovery and relative standard deviation (RSD). The recovery of Cu2+ ions at each concentration for the water samples was statistically close
Fig. 4. Time-dependent fluorescence response of sensor CHT (black line) and sensor CHT with the addition 5eqiv Cu2+ ions (red line) in aqueous acetonitrile (1:1, v/v). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
fluorescence signals of sensor CHT was apparent stability within 40mins. In the same conditions, sensor CHT was added into acetonitrile and PBS solution and then 5 equiv Cu2+ ions were added into solution. As shown in Fig. 4, a stable fluorescence signal was observed with the
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Fig. 5. (a) Fluorescence response of the probe (2 μM) in the presence of various relevant cations (10 μM) that are abundant in cells in acetonitrile/PBS buffer (1:1, v/v, pH = 7.4). (b) The dungaree bars represent the emission intensities of sensor CHT in the presence of 10 μM other common cations respectively. The wine bars represent the change in emission upon subsequent addition of 10 μM of Cu2+ to the above solution with an excitation at 450 nm and emission at 540 nm.
Fig. 6. Relative growth rate (%) was estimated by the CCK8 assay. (a) The sensor CHT was cultured in the A549 cells for 24 h. (b) The sensor CHT was cultured in the MCF-7 cells for 24 h.
Table 1 Results of the recognition of Cu2+ in actual water samples.
to 100% (range from 92.90% to 109.03%), showing future practical applicability of probe for Cu2+ ions recognition in real samples analysis. The ability of sensor CHT to track Cu2+ ions in living cells was measured through confocal microscopy. The A549 cells and MCF-7 cells were incubated with 1 μM sensor CHT for 20 min, and then added varied concentration of Cu2+ ions (0, 0.5, 1 and 2 μM) for another 20 min. The cells were washed three times with PBS buffer before imaging with confocal laser scanning microscopy. The cells exhibited strong fluorescence when induced by excitation light source of 458 nm, and cells treated with Cu2+ ions (2 μM) showed fluorescence quenching (Fig. 7). The confocal microscopy images strongly suggested that fluorescent sensor CHT was successfully applied for fluorescent imaging of Cu2+ in living cells. In conclusion, a novel fluorescent sensor CHT has been designed and synthesized, which based on a schiff base condensation of 7-(N,N-
Spiked (μM) 1 2 3
Found (μM)
Recovery (100%)
RSD (%) (n = 3)
1.0926 1.9361 2.7869
109.3 96.80 92.90
2.00 1.17 0.87
diethylamino) coumarin-3-aldehyde and 2-hydrazinobenzothiazole. As a fluorescent sensor, CHT exhibited a significant fluorescence quenching at 540 nm upon the addition of Cu2+ ions. In the presence of other important relevant metal ions in acetonitrile/PBS buffer (1:1, v/v, pH = 7.4), sensor CHT exhibited high selectivity towards Cu2+ ions. The sensor CHT could recognize Cu2+ ions under physiological pH conditions and has been successfully utilized for fluorescence imaging of Cu2+ ions in biological system.
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Fig. 7. Confocal microscpy images of cells incubated with sensor CHT and Cu2+. (a1, a2, a3, a4) Fluorescent images of sensor CHT (1 μM) treated A549 cells and incubated with Cu2+ (0 μM, 0.5 μM, 1 μM, 2 μM) respectively. (b1, b2, b3, b4) Fluorescent images of sensor CHT (1 μM) treated MCF-7 cells and incubated with Cu2+ (0 μM, 0.5 μM, 1 μM, 2 μM) respectively. Excitation was at 458 nm.
Acknowledgments
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