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Synthesis of a new binuclear silver(I) complex with the ability to interact with DNA molecule
Journal Pre-proofs Synthesis of a new binuclear silver(I) complex with the ability to interact with DNA molecule Lan-Xing Gao, Deng-Ze Wu, Fahime Bigdeli, Qian Miao, Mao-Lin Hu, Ali Morsali PII: DOI: Reference:
S0167-577X(19)31831-2 https://doi.org/10.1016/j.matlet.2019.127199 MLBLUE 127199
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
2 August 2019 8 December 2019 17 December 2019
Please cite this article as: L-X. Gao, D-Z. Wu, F. Bigdeli, Q. Miao, M-L. Hu, A. Morsali, Synthesis of a new binuclear silver(I) complex with the ability to interact with DNA molecule, Materials Letters (2019), doi: https://doi.org/ 10.1016/j.matlet.2019.127199
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2019 Published by Elsevier B.V.
Synthesis of a new binuclear silver(I) complex with the ability to interact with DNA molecule Lan-Xing Gao a, Deng-Ze Wu a,*, Fahime Bigdeli b, Qian Miao a, Mao-Lin Hu Morsali b, * a
a,*,
Ali
College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou
325035, People's Republic of China b
Department of Chemistry, Faculty of Sciences, Tarbiat Modares University, P.O. Box
14115-175, Tehran, Iran Corresponding authors: E-mail addresses: [email protected] (D.-Z. Wu), [email protected] (M.-L.
Hu), [email protected] (A. Morsali). Abstract A
new
binuclear
silver
complex,
[Ag2(FcCOO)2(dppm)2].2CH3CN,
Fc-COOH=ferrocenecarboxylic acid, dppm= bis(diphenylphosphino)methane, with the ability to form binding with DNA molecule, was synthesized and its structure determined by elemental analysis, FT-IR,
13C
NMR,
31P
NMR and X-ray
crystallography. Considering the potential of the complex A1 in the cancer treatment, the interaction of this complex with calf thymus DNA (CT-DNA) was investigated by using electronic absorption spectra, fluorescence and redox behavior techniques. The experimental results showed that there is an electrostatic interaction between complex and CT-DNA. Keywords: silver(I) complex; crystal structure; ferrocenecarboxylic acid; DNA; electrical properties 1. Introduction In the recent years, the researches on the silver complexes have gained a wide 1
consideration due to their extensive applications in effective antibacterial, anticancer and antifungal drugs, catalysis, and luminescent materials [1-4]. Silver complexes display the anticancer properties into cells of humans. One of the main functions of the anticancer agents in the cell is via effect on DNA molecule [5]. Some small molecules can interact with DNA and disrupt its operations, by disturbing gene sequence and/or protein synthesis process and interfering replication [6]. It has been proved that binuclear type silver complexes represent the more biological activity and cytotoxicity against cancer cells [7]. In
this
report,
we
choose
ferrocenecarboxylic
acid,
silver
triflate
and
bis(diphenylphosphino)methane for preparation of a binuclear silver complex. Also, the interaction of this complex with CT-DNA was investigated. 2. Experimental 2.1. Synthesis and crystallization 2.1.1. Materials and physical measurements Silver triflate (AgOTf) and ferrocenecarboxylic acid (Fc-COOH) were purchased from Sigma–Aldrich, Shanghai. All other chemicals and solvents employed were commercially available and used as received. The FT-IR spectra were recorded from KBr pellets in the range 4000-400 cm-1 with a WQF-520A FT-IR spectrometer. Microanalysis (C, H and N) was carried out with a CE instruments EA 1110 elemental analyzer. 1H-NMR (500 MHz),
13C-NMR
(125 MHz) and
31P
NMR (202
MHz) spectra were measured on a Bruker spectrometer (Billerica, MA, USA), using DMSO as the solvent with tetramethylsilane (TMS) as the internal standard at room 2
temperature. Chemical shifts are given in δ relative to TMS; the coupling constants J are given in Hz. 2.1.2. Synthesis of ferrocene carboxy silver(I) complex（A1） To the 20 mL reaction bulb, 0.069 g (0.3 mmol) Fc-COOH (ferrocenecarboxylic acid) and 0.077 g (0.3 mmol) AgOTf (silver triflate) were dissolved in a mixture of methanol/acetonitrile (6 mL, 1:1 v/v). To the stirring solution, 0.058g (0.15mmol) dppm (bis(diphenylphosphino)methane) was added, then 42μL triethylamine was added to make the reaction environment alkaline. The solution was stirred at 65°C for 30min until the reactants were completely dissolved and then was put in the reaction furnace at 70℃ for 12h. After cooling to room temperature, the solution filtrated immediately to remove the unreacted drugs. The filtrate left for slow evaporation under 3℃ in the dark, clear crystals formed after 3-4 days. The crystallite was collected by filtration, washed with ethanol and dried in vacuum. Yield: 90.90%. M. p: 242.2ºC, Anal. Calc. For C72H62O4P4Fe2Ag2 (%): C, 59.89; H, 4.27; N, 0. Found (%): C, 59.92; H, 4.30; N, 0. IR, 13C NMR and 31P NMR data (Figs S1-S3) and the methods of the structure refinement details of the complex is observed in Supporting Information. 2.4. DNA binding experiments 2.4. 1. Electronic absorption spectra studies UV-Vis absorption spectroscopy is commonly used to investigate the interactions between DNA and small molecules. The concentration of 10 μM from A1 was titrated with variable concentrations of CT-DNA (0, 0.005, 0.01, 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, 0.045 mg.mL-1) in KH2PO4/NaOH buffer and absorption data were recorded. The absorption spectru are given in Figs. 2 and S4. 3
2.4.2. Fluorescence studies Fluorescence property is used to study the existing interactions between DNA and complex. Herein, the EthBr-CT-DNA fluorescence property has been investigated. Emission spectra of EthBr (0.05 mM) bound to CT-DNA (0.12 mg.mL-1) has been recorded in the absence and presence of varying concentration of complex (0.00-0.10 mM) in 0.1 M Tris-HCl/ 0.1 M NaCl buffer (pH = 7.2). It is observed that the EthBr -CT-DNA emission bands are influenced by increasing the concentration of the complex (Fig. 3). 2.4.3. Electrochemical characterization In order to further investigate the interaction essence between the complex and CT-DNA, the electrochemical methods were used to study the redox behavior complex-CT-DNA. The typical cyclic voltammograms of the complex in the absence and presence of CT-DNA are shown in Figs. S5 and S6. The cyclic voltammograms of the complex for A1 (3 mM) at different scan rates (0.1–0.6 vs−1) and in the presence of CT-DNA (0.1 mg.mL−1) were recorded. The parameter of diffusion coefficient for the free A1 (3 mM) by plots of Ip vs. v1/2 were obtained. 3. Results and discussion 3.1. Structural characterization Reaction between silver triflate with Fc-COOH and dppm in methanol/acetonitrile, with stoichiometries of 1: 1: 0.5, respectively, led to the formation of binuclear silver complex with formula of [Ag2(FcCOO)2(dppm)2].2CH3CN. A1 consists of triclinic 4
unit with Pī space group. Each structural unit of the complex A1 contains two silver atoms with Ag−Ag distance of 2.9352(9) Å. Ag(1) atom includs a distorted tetrahedral geometry surrounded by two phosphorus atoms from individual molecules, one carboxylate oxygen atom and Ag2. Ag(2) atom possesses the coordination environment of distorted square pyramidal contain two carboxylate oxygen atoms from different ferrocenecarboxylat anions, two phosphorus atoms from distinct molecules and Ag1 (Fig. 1). A ferrocenecarboxylat anion by one carboxylate oxygen atom as monodentate is connected to Ag(2) and carboxylate anion belong to the other ferrocenecarboxylat anion is coordinated as bidentate to Ag(1) and Ag(2) metal ions. The crystallographic data and description of the structure refinement are given in (Table S1). The structure data have been deposited with the CCDC reference 1881513 which is available on https://www.ccdc.cam.ac.uk/structures.
Fig. 1. Representation of molecular diagram of [Ag2(FcCOO)2(dppm)2].2CH3CN. (A1)
3.2. DNA binding studies The binding DNA with A1 was studied by following spectroscopic techniques. 3.2.1. Electronic absorption spectra studies The absorption spectra of the complex incubated with increasing concentrations 5
of CT-DNA (Figs. 2 and S4). The intensities of the absorption bands for the complex A1 increased which might be ascribed to the electrostatic interaction between the metal ion of the complex and phosphate group of DNA [8]. The higher Kb value for pH = 7.2 (Fig. 2) compared to pH = 6.2 or pH = 8.2 (Fig. S4) indicates that the bond
strength of complex to DNA in a neutral environment is stronger than both acidic and alkaline environments. This is because of the influence of the acidic and alkaline environments on the complex.
Fig.2. Electronic absorption spectra of A1 (10 μM) in the absence and presence of increasing amounts of CT-DNA (0, 0.005, 0.01, 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, 0.045 mg·mL-1) in KH2PO4 / NaOH buffer pH = 6.2. Inset: Plot of A0/A-A0 vs.1/ [DNA] for the titration of the A1 with CT-DNA. The binding constants (Kb) of complex A1 are calculated as 22.45 mg.mL-1.
3.2.2. Fluorescence studies The fluorescence quenching efficiency is evaluated by the Stern-Volmer constant (KSV) based on the classical Stern-Volmer equation: F0/F = 1 + KSV[Q] that F0 and F are the fluorescence intensities of EthBr-DNA in the absence and presence of the complex, respectively, and [Q] is the concentration of the complex. KSV is a linear Stern-Volmer quenching constant that is achieved from the linear regression of F0/F with [Q]. As shown in Fig. 3, the decrease of the emission band intensity in the 6
EthBr-DNA system with an increase in the concentration of the complex, suggested that the complex can be a substitute for EthBr at DNA binding sites [9].
Fig.3. Emission spectra of EthBr (0.05 mM) bound to CT-DNA (0.12 mg. mL-1) in the absence and presence of A1 (0.00, 0.02, 0.04, 0.06, 0.08, 0.10 mM) in KH2PO4 / NaOH buffer (pH = 7.2). Inset: Stern-Volmer quenching curve. The obtained KSV values for complex were found to be 5.432 × 103 M-1 .
3.2.3. Electrochemical characterization The redox behavior of the metal complex and DNA was investigated by the typical cyclic voltammograms of the complex in the absence and presence of CT-DNA (Figs. S5 and S6). It is not observed any new peaks after the addition of CT-DNA to the complex, albeit there is a significant increase in Ipc, indicating that the complex is bound to DNA. With the increase of scan rate, the peak potential showed a gradual shift in negative direction. Generally, when the metal complex binds DNA via electrostatic interaction, the electrochemical potential of the complex will shift in a negative direction. In addition, there was a positive correlation between Ipc and ν1/2 which may be related to the weak adsorption on the surface of the electrode. 4. Conclusion In this report, a new binuclear silver complex, [Ag2(FcCOO)2(dppm)2].2CH3CN, including two silver ion centers with different coordination environments was prepared and characterized. By using diphosphine chelating ligand, that can form bridging between two metal ions, it has been possible to prepare binuclear structure. 7
The binding of the complex A1 with CT-DNA was investigated by techniques including electronic absorption spectra, fluorescence and redox behavior via cyclic voltammograms and the results showed an electrostatic interaction mode for complex with DNA. Funding information Support of this investigation by the National Natural Science (Nos. 21371137 and 21571143) and Tarbiat
Foundation of China
Modares University is gratefully
acknowledged. References: [1] A.R. Abbasi, A. Morsali, Formation of silver iodide nanoparticles on silk fiber by means of ultrasonic irradiation, Ultrasonics sonochemistry, 17 (2010) 704-710. [2] X. Liang, S. Luan, Z. Yin, M. He, C. He, L. Yin, Y. Zou, Z. Yuan, L. Li, X. Song, Recent advances in the medical use of silver complex, European journal of medicinal chemistry, 157 (2018) 62-80. [3] L.R. Favarin, L. Oliveira, H. Silva, A. Micheletti, L. Pizzuti, A. Machulek-Júnior, A.R. Caires, D.F. Back, S. Lima, L. Andrade, Sonochemical synthesis of highly luminescent silver complexes: Photophysical properties and preliminary in vitro antitumor and antibacterial assays, Inorganica Chimica Acta, 492 (2019) 235-242. [4] A.S. Romanov, M. Bochmann, Synthesis, structures and photoluminescence properties of silver complexes of cyclic (alkyl)(amino) carbenes, Journal of Organometallic Chemistry, 847 (2017) 114-120. [5] N. Kasyanenko, Z. Qiushi, V. Bakulev, M. Osolodkov, P. Sokolov, V. Demidov, DNA binding with acetate bis (1, 10-phenanthroline) silver(I) monohydrate in a solution and metallization of formed structures, Polymers, 9 (2017) 211. [6] J.L. García-Giménez, J. Hernández-Gil, A. Martínez-Ruíz, A. Castiñeiras, M. Liu-González, F.V. Pallardó, J. Borrás, G.A. Piña, DNA binding, nuclease activity, DNA photocleavage and cytotoxic properties of Cu(II) complexes of N-substituted sulfonamides, Journal of inorganic biochemistry, 121 (2013) 167-178. [7] M.A. Iqbal, M.I. Umar, R.A. Haque, M.B.K. Ahamed, M.Z.B. Asmawi, A.M.S.A. Majid, Macrophage and colon tumor cells as targets for a binuclear silver(I) N-heterocyclic carbene complex, an anti-inflammatory and apoptosis mediator, Journal of inorganic biochemistry, 146 (2015) 1-13. [8] L. Kyros, C. Banti, N. Kourkoumelis, M. Kubicki, I. Sainis, S. Hadjikakou, Synthesis, characterization, and binding properties towards CT-DNA and lipoxygenase of mixed-ligand silver (I) complexes with 2-mercaptothiazole and its derivatives and triphenylphosphine, JBIC Journal of Biological Inorganic Chemistry, 19 (2014) 449-464. [9] J. Olmsted III, D.R. Kearns, Mechanism of ethidium bromide fluorescence enhancement on binding to nucleic acids, Biochemistry, 16 (1977) 3647-3654.
8
9
10
Highlights ● Synthesis and characterization of a novel binuclear silver complex ● Investigation of the interaction ability of the complex with CT-DNA molecule ● Characterization of the binding nature of the complex to CT-DNA
Declaration of interests
☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
11
The authors report no conflicts of interest in this work.
Author Contributions Section
Lan-Xing Gao: Investigation, Deng-Ze Wu: Formal analysis, Fahime Bigdeli: Writing - Original Draft, Review & Editing, Qian Miao: Software, Mao-Lin Hu: Supervision, Ali Morsali: Supervision
12
S0167-577X(19)31831-2 https://doi.org/10.1016/j.matlet.2019.127199 MLBLUE 127199
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
2 August 2019 8 December 2019 17 December 2019
Please cite this article as: L-X. Gao, D-Z. Wu, F. Bigdeli, Q. Miao, M-L. Hu, A. Morsali, Synthesis of a new binuclear silver(I) complex with the ability to interact with DNA molecule, Materials Letters (2019), doi: https://doi.org/ 10.1016/j.matlet.2019.127199
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2019 Published by Elsevier B.V.
Synthesis of a new binuclear silver(I) complex with the ability to interact with DNA molecule Lan-Xing Gao a, Deng-Ze Wu a,*, Fahime Bigdeli b, Qian Miao a, Mao-Lin Hu Morsali b, * a
a,*,
Ali
College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou
325035, People's Republic of China b
Department of Chemistry, Faculty of Sciences, Tarbiat Modares University, P.O. Box
14115-175, Tehran, Iran Corresponding authors: E-mail addresses: [email protected] (D.-Z. Wu), [email protected] (M.-L.
Hu), [email protected] (A. Morsali). Abstract A
new
binuclear
silver
complex,
[Ag2(FcCOO)2(dppm)2].2CH3CN,
Fc-COOH=ferrocenecarboxylic acid, dppm= bis(diphenylphosphino)methane, with the ability to form binding with DNA molecule, was synthesized and its structure determined by elemental analysis, FT-IR,
13C
NMR,
31P
NMR and X-ray
crystallography. Considering the potential of the complex A1 in the cancer treatment, the interaction of this complex with calf thymus DNA (CT-DNA) was investigated by using electronic absorption spectra, fluorescence and redox behavior techniques. The experimental results showed that there is an electrostatic interaction between complex and CT-DNA. Keywords: silver(I) complex; crystal structure; ferrocenecarboxylic acid; DNA; electrical properties 1. Introduction In the recent years, the researches on the silver complexes have gained a wide 1
consideration due to their extensive applications in effective antibacterial, anticancer and antifungal drugs, catalysis, and luminescent materials [1-4]. Silver complexes display the anticancer properties into cells of humans. One of the main functions of the anticancer agents in the cell is via effect on DNA molecule [5]. Some small molecules can interact with DNA and disrupt its operations, by disturbing gene sequence and/or protein synthesis process and interfering replication [6]. It has been proved that binuclear type silver complexes represent the more biological activity and cytotoxicity against cancer cells [7]. In
this
report,
we
choose
ferrocenecarboxylic
acid,
silver
triflate
and
bis(diphenylphosphino)methane for preparation of a binuclear silver complex. Also, the interaction of this complex with CT-DNA was investigated. 2. Experimental 2.1. Synthesis and crystallization 2.1.1. Materials and physical measurements Silver triflate (AgOTf) and ferrocenecarboxylic acid (Fc-COOH) were purchased from Sigma–Aldrich, Shanghai. All other chemicals and solvents employed were commercially available and used as received. The FT-IR spectra were recorded from KBr pellets in the range 4000-400 cm-1 with a WQF-520A FT-IR spectrometer. Microanalysis (C, H and N) was carried out with a CE instruments EA 1110 elemental analyzer. 1H-NMR (500 MHz),
13C-NMR
(125 MHz) and
31P
NMR (202
MHz) spectra were measured on a Bruker spectrometer (Billerica, MA, USA), using DMSO as the solvent with tetramethylsilane (TMS) as the internal standard at room 2
temperature. Chemical shifts are given in δ relative to TMS; the coupling constants J are given in Hz. 2.1.2. Synthesis of ferrocene carboxy silver(I) complex（A1） To the 20 mL reaction bulb, 0.069 g (0.3 mmol) Fc-COOH (ferrocenecarboxylic acid) and 0.077 g (0.3 mmol) AgOTf (silver triflate) were dissolved in a mixture of methanol/acetonitrile (6 mL, 1:1 v/v). To the stirring solution, 0.058g (0.15mmol) dppm (bis(diphenylphosphino)methane) was added, then 42μL triethylamine was added to make the reaction environment alkaline. The solution was stirred at 65°C for 30min until the reactants were completely dissolved and then was put in the reaction furnace at 70℃ for 12h. After cooling to room temperature, the solution filtrated immediately to remove the unreacted drugs. The filtrate left for slow evaporation under 3℃ in the dark, clear crystals formed after 3-4 days. The crystallite was collected by filtration, washed with ethanol and dried in vacuum. Yield: 90.90%. M. p: 242.2ºC, Anal. Calc. For C72H62O4P4Fe2Ag2 (%): C, 59.89; H, 4.27; N, 0. Found (%): C, 59.92; H, 4.30; N, 0. IR, 13C NMR and 31P NMR data (Figs S1-S3) and the methods of the structure refinement details of the complex is observed in Supporting Information. 2.4. DNA binding experiments 2.4. 1. Electronic absorption spectra studies UV-Vis absorption spectroscopy is commonly used to investigate the interactions between DNA and small molecules. The concentration of 10 μM from A1 was titrated with variable concentrations of CT-DNA (0, 0.005, 0.01, 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, 0.045 mg.mL-1) in KH2PO4/NaOH buffer and absorption data were recorded. The absorption spectru are given in Figs. 2 and S4. 3
2.4.2. Fluorescence studies Fluorescence property is used to study the existing interactions between DNA and complex. Herein, the EthBr-CT-DNA fluorescence property has been investigated. Emission spectra of EthBr (0.05 mM) bound to CT-DNA (0.12 mg.mL-1) has been recorded in the absence and presence of varying concentration of complex (0.00-0.10 mM) in 0.1 M Tris-HCl/ 0.1 M NaCl buffer (pH = 7.2). It is observed that the EthBr -CT-DNA emission bands are influenced by increasing the concentration of the complex (Fig. 3). 2.4.3. Electrochemical characterization In order to further investigate the interaction essence between the complex and CT-DNA, the electrochemical methods were used to study the redox behavior complex-CT-DNA. The typical cyclic voltammograms of the complex in the absence and presence of CT-DNA are shown in Figs. S5 and S6. The cyclic voltammograms of the complex for A1 (3 mM) at different scan rates (0.1–0.6 vs−1) and in the presence of CT-DNA (0.1 mg.mL−1) were recorded. The parameter of diffusion coefficient for the free A1 (3 mM) by plots of Ip vs. v1/2 were obtained. 3. Results and discussion 3.1. Structural characterization Reaction between silver triflate with Fc-COOH and dppm in methanol/acetonitrile, with stoichiometries of 1: 1: 0.5, respectively, led to the formation of binuclear silver complex with formula of [Ag2(FcCOO)2(dppm)2].2CH3CN. A1 consists of triclinic 4
unit with Pī space group. Each structural unit of the complex A1 contains two silver atoms with Ag−Ag distance of 2.9352(9) Å. Ag(1) atom includs a distorted tetrahedral geometry surrounded by two phosphorus atoms from individual molecules, one carboxylate oxygen atom and Ag2. Ag(2) atom possesses the coordination environment of distorted square pyramidal contain two carboxylate oxygen atoms from different ferrocenecarboxylat anions, two phosphorus atoms from distinct molecules and Ag1 (Fig. 1). A ferrocenecarboxylat anion by one carboxylate oxygen atom as monodentate is connected to Ag(2) and carboxylate anion belong to the other ferrocenecarboxylat anion is coordinated as bidentate to Ag(1) and Ag(2) metal ions. The crystallographic data and description of the structure refinement are given in (Table S1). The structure data have been deposited with the CCDC reference 1881513 which is available on https://www.ccdc.cam.ac.uk/structures.
Fig. 1. Representation of molecular diagram of [Ag2(FcCOO)2(dppm)2].2CH3CN. (A1)
3.2. DNA binding studies The binding DNA with A1 was studied by following spectroscopic techniques. 3.2.1. Electronic absorption spectra studies The absorption spectra of the complex incubated with increasing concentrations 5
of CT-DNA (Figs. 2 and S4). The intensities of the absorption bands for the complex A1 increased which might be ascribed to the electrostatic interaction between the metal ion of the complex and phosphate group of DNA [8]. The higher Kb value for pH = 7.2 (Fig. 2) compared to pH = 6.2 or pH = 8.2 (Fig. S4) indicates that the bond
strength of complex to DNA in a neutral environment is stronger than both acidic and alkaline environments. This is because of the influence of the acidic and alkaline environments on the complex.
Fig.2. Electronic absorption spectra of A1 (10 μM) in the absence and presence of increasing amounts of CT-DNA (0, 0.005, 0.01, 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, 0.045 mg·mL-1) in KH2PO4 / NaOH buffer pH = 6.2. Inset: Plot of A0/A-A0 vs.1/ [DNA] for the titration of the A1 with CT-DNA. The binding constants (Kb) of complex A1 are calculated as 22.45 mg.mL-1.
3.2.2. Fluorescence studies The fluorescence quenching efficiency is evaluated by the Stern-Volmer constant (KSV) based on the classical Stern-Volmer equation: F0/F = 1 + KSV[Q] that F0 and F are the fluorescence intensities of EthBr-DNA in the absence and presence of the complex, respectively, and [Q] is the concentration of the complex. KSV is a linear Stern-Volmer quenching constant that is achieved from the linear regression of F0/F with [Q]. As shown in Fig. 3, the decrease of the emission band intensity in the 6
EthBr-DNA system with an increase in the concentration of the complex, suggested that the complex can be a substitute for EthBr at DNA binding sites [9].
Fig.3. Emission spectra of EthBr (0.05 mM) bound to CT-DNA (0.12 mg. mL-1) in the absence and presence of A1 (0.00, 0.02, 0.04, 0.06, 0.08, 0.10 mM) in KH2PO4 / NaOH buffer (pH = 7.2). Inset: Stern-Volmer quenching curve. The obtained KSV values for complex were found to be 5.432 × 103 M-1 .
3.2.3. Electrochemical characterization The redox behavior of the metal complex and DNA was investigated by the typical cyclic voltammograms of the complex in the absence and presence of CT-DNA (Figs. S5 and S6). It is not observed any new peaks after the addition of CT-DNA to the complex, albeit there is a significant increase in Ipc, indicating that the complex is bound to DNA. With the increase of scan rate, the peak potential showed a gradual shift in negative direction. Generally, when the metal complex binds DNA via electrostatic interaction, the electrochemical potential of the complex will shift in a negative direction. In addition, there was a positive correlation between Ipc and ν1/2 which may be related to the weak adsorption on the surface of the electrode. 4. Conclusion In this report, a new binuclear silver complex, [Ag2(FcCOO)2(dppm)2].2CH3CN, including two silver ion centers with different coordination environments was prepared and characterized. By using diphosphine chelating ligand, that can form bridging between two metal ions, it has been possible to prepare binuclear structure. 7
The binding of the complex A1 with CT-DNA was investigated by techniques including electronic absorption spectra, fluorescence and redox behavior via cyclic voltammograms and the results showed an electrostatic interaction mode for complex with DNA. Funding information Support of this investigation by the National Natural Science (Nos. 21371137 and 21571143) and Tarbiat
Foundation of China
Modares University is gratefully
acknowledged. References: [1] A.R. Abbasi, A. Morsali, Formation of silver iodide nanoparticles on silk fiber by means of ultrasonic irradiation, Ultrasonics sonochemistry, 17 (2010) 704-710. [2] X. Liang, S. Luan, Z. Yin, M. He, C. He, L. Yin, Y. Zou, Z. Yuan, L. Li, X. Song, Recent advances in the medical use of silver complex, European journal of medicinal chemistry, 157 (2018) 62-80. [3] L.R. Favarin, L. Oliveira, H. Silva, A. Micheletti, L. Pizzuti, A. Machulek-Júnior, A.R. Caires, D.F. Back, S. Lima, L. Andrade, Sonochemical synthesis of highly luminescent silver complexes: Photophysical properties and preliminary in vitro antitumor and antibacterial assays, Inorganica Chimica Acta, 492 (2019) 235-242. [4] A.S. Romanov, M. Bochmann, Synthesis, structures and photoluminescence properties of silver complexes of cyclic (alkyl)(amino) carbenes, Journal of Organometallic Chemistry, 847 (2017) 114-120. [5] N. Kasyanenko, Z. Qiushi, V. Bakulev, M. Osolodkov, P. Sokolov, V. Demidov, DNA binding with acetate bis (1, 10-phenanthroline) silver(I) monohydrate in a solution and metallization of formed structures, Polymers, 9 (2017) 211. [6] J.L. García-Giménez, J. Hernández-Gil, A. Martínez-Ruíz, A. Castiñeiras, M. Liu-González, F.V. Pallardó, J. Borrás, G.A. Piña, DNA binding, nuclease activity, DNA photocleavage and cytotoxic properties of Cu(II) complexes of N-substituted sulfonamides, Journal of inorganic biochemistry, 121 (2013) 167-178. [7] M.A. Iqbal, M.I. Umar, R.A. Haque, M.B.K. Ahamed, M.Z.B. Asmawi, A.M.S.A. Majid, Macrophage and colon tumor cells as targets for a binuclear silver(I) N-heterocyclic carbene complex, an anti-inflammatory and apoptosis mediator, Journal of inorganic biochemistry, 146 (2015) 1-13. [8] L. Kyros, C. Banti, N. Kourkoumelis, M. Kubicki, I. Sainis, S. Hadjikakou, Synthesis, characterization, and binding properties towards CT-DNA and lipoxygenase of mixed-ligand silver (I) complexes with 2-mercaptothiazole and its derivatives and triphenylphosphine, JBIC Journal of Biological Inorganic Chemistry, 19 (2014) 449-464. [9] J. Olmsted III, D.R. Kearns, Mechanism of ethidium bromide fluorescence enhancement on binding to nucleic acids, Biochemistry, 16 (1977) 3647-3654.
8
9
10
Highlights ● Synthesis and characterization of a novel binuclear silver complex ● Investigation of the interaction ability of the complex with CT-DNA molecule ● Characterization of the binding nature of the complex to CT-DNA
Declaration of interests
☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
11
The authors report no conflicts of interest in this work.
Author Contributions Section
Lan-Xing Gao: Investigation, Deng-Ze Wu: Formal analysis, Fahime Bigdeli: Writing - Original Draft, Review & Editing, Qian Miao: Software, Mao-Lin Hu: Supervision, Ali Morsali: Supervision
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