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Methylene blue-based distinguishing DNA conformation for colorimetric detection of silver ions
Microchemical Journal 147 (2019) 995–998
Contents lists available at ScienceDirect
Microchemical Journal journal homepage: www.elsevier.com/locate/microc
Methylene blue-based distinguishing DNA conformation for colorimetric detection of silver ions☆
T
Song Xua, , Xiaojuan Chena, Xin Chena, Yong Liangb ⁎
a b
School of Environment and Chemical Engineering, Foshan University, Foshan 528000, China School of Chemistry and Environment, South China Normal University, Guangzhou 510631, China
ARTICLE INFO
ABSTRACT
Keywords: Silver ion Colorimetric Single-stranded Methylene blue C-Ag+-C formation
A highly sensitive colorimetric sensing strategy based on the interaction between methylene blue (MB) and Crich single-stranded DNA (ssDNA) (24C used here) has been developed for detection of Ag+. In the absence of target Ag+, the interaction between MB and 24C makes the color immediately change from blue to purple. However, specific C-Ag+-C pair forms when Ag+ ions are present in the aqueous solution containing 24C and MB, resulting in the desorption of MB from the surface of 24C into the solution. As a result, the color changes from purple to blue, and the absorbance values of MB at 660 and 605 nm gradually decrease. The detection limit can be as low as 1 nM, which satisfies the guideline concentration of Ag+ in drinking water set by the United States Environmental Protection Agency (EPA). The practical use of this method for Ag+ detection in river water samples is also demonstrated successfully.
1. Introduction Among biologically important metal ions, silver ion (Ag+) has always drawn considerable attention due to its antimicrobial and toxic activities. Ag+ at low concentration shows strong antimicrobial activity [1]. However, high concentrations of Ag+ exhibit serious biological effects on human health, such as urine silver excretion and blood silver (argyria), cardiac enlargement, growth retardation, and degenerative changes in the liver [2,3]. Therefore, it is vital to develop the sensing strategy of Ag+ with high sensitivity and selectivity. A variety of detection methods, such as atomic absorption spectrometry [4], inductively coupled plasma-mass spectroscopy [5], plasma atomic emission spectrometry [6], and fluorescence [7–10], electrochemistry [11–13], have been developed for the detection of Ag+. These methods have been successfully used to detect trace levels of Ag+, however, they generally require complicated protocols, sophisticated instruments, and skilled operators. Thus, such requirements largely limit practical applications of these methods, especially in resource-limited areas. Alternatively, colorimetric methods [14,15] have been widely used to detect Ag+ because they can be easily operated by less-trained personnel with an inexpensive spectrophotometer or even the bared eye [16–24]. Nevertheless, the methods usually involve complex synthesis of nanomaterials.
In this paper, we present a simple but effective colorimetric assay for Ag+ detection based on the specific interaction between methylene blue (MB) and C-rich single-stranded DNA (ssDNA) (here 24C). The specific interaction mainly relies on the sequence of ssDNA, in which more than 3 consecutive C bases are needed. The sequence and structure dual-dependent interaction mode inspires us to come up with the idea for Ag+ sensing. Without target Ag+, MB molecules are absorbed on the surface of 24C, leading to color change of MB from blue to purple. Whereas in the presence of target Ag+, the specific C-Ag+-C coordination impels MB absorbed on 24C surface to remove off, it returns to its own blue. Therefore, the C-Ag+-C coordination affects the interaction between MB and 24C, further affecting the colorimetric signals of MB. By taking advantage of diverse colorimetric signal induced by the interaction, highly sensitive and selective detection of Ag+ is realized. 2. Experimental section 2.1. Reagents and chemicals Methylene blue (MB), and trisodium citrate, ethylenediaminetetraacetic acid disodium salt dehydrate (EDTA), were purchased from Sigma-Aldrich. 5′-CCC CCC CCC CCC CCC CCC CCC CCC-3′ (24C) were
Selected papers from the XVI Hungarian – Italian Symposium on Spectrochemistry: Technological innovation for water science and sustainable aquatic biodiversity, 3-6th October 2018, Budapest. ⁎ Corresponding author. E-mail addresses: [email protected] (S. Xu), [email protected] (Y. Liang). ☆
https://doi.org/10.1016/j.microc.2019.04.019 Received 15 March 2019; Received in revised form 4 April 2019; Accepted 4 April 2019 Available online 05 April 2019 0026-265X/ © 2019 Elsevier B.V. All rights reserved.
Microchemical Journal 147 (2019) 995–998
S. Xu, et al.
Scheme 1. Mechanism of the interaction between MB and aptamer-based colorimetric probe for Ag+ detection.
Fig. 1. (A) Changes of absorption spectra after the addition of Ag+ with various concentrations ranging from 0 to 1 μM. (B) Linear calibration plot for Ag+ detection. Inset: Color change corresponding to different concentration of Ag+.
temperature. 3. Results and discussion 3.1. Detection mechanism The proposed mechanism of colorimetric probe for Ag+ detection based on the interaction between MB and aptamer-based is shown in Scheme 1. It is found that in the absence of target Ag+, MB can interact with cytosine (C)-rich single-stranded DNA (ssDNA) (24C), the solution color changes from blue to purple. However, in the presence of target Ag+, an interaction between MB and 24C occurs, which liberates MB into the solution. Thus, the solution color undergoes a change from purple to blue. Relying on C-Ag+-C formation-induced color change, the assay successfully quantifies Ag+ selectively and sensitively.
Fig. 2. Absorbance change of MB solution in the presence of different individual metal ions (the concentration of interfering metal ions was 100-fold higher than that of Ag+). Inset: the corresponding color of metal ion solution.
3.2. Analytical performances for Ag+ detection
Ultraviolet-visible (UV–vis) absorption spectrum measurement was carried out by an UV-2550 Spectrophotometer (Shimadzu Corporation).
Under the optimized conditions mentioned above, the linear response range of the assay was measured. As displayed in Fig. 1A, with the increase of the added Ag+, the absorption peak at 660 and 605 nm is gradually decreased. Fig. 1B shows a good linear relationship between the ΔA660 and the logarithmic value of Ag+ concentrations from 1 nM to 1 μM. Thus, it can be concluded that our colorimetric probe can be used for the quantitative determination of Ag+ and the limit of detection (LOD) is 1 nM with the naked-eye, which is much lower than the threshold value of silver (∼460 nM) in drinking water permitted by the United States Environmental Protection Agency (EPA).
2.3. The procedure of Ag+ detection
3.3. Specificity test
First, 10 μL of 100 μM 24C and 50 μL of 200 μM MB were mixed with 70 μLTE buffer (10 mM Tris, 1 mM EDTA, pH 7.7). Then, 5 μL of Ag+ standard solutions with different concentrations were added, respectively. The absorbance of the above solutions was measured at room
We also studied the selectivity of the assay for Ag+ sensing. Common metal ions including Cd2+, Hg2+, Pb2+, Cu2+, Sn4+, Ni2+, Fe3+, and Mn2+, each at a concentration of 3 μM, as interfering ions were tested using the standard procedure. As shown in Fig. 2, in
synthesized by Sangon Biotechnology Co. Ltd. (Shanghai, China). All other reagents were of analytical reagent grade and directly used without additional purification. Ultrapure water was provided by a Direct-Q3 system and used as a solvent in all experiments. 2.2. Instrumentation
996
Microchemical Journal 147 (2019) 995–998
S. Xu, et al.
Fig. 3. (A) UV–vis absorption spectra of MB solutions incubated with different concentrations of Ag+ in the presence of 100 μM aptamer. (B) The ΔA660 versus different Ag+ concentrations in the range of 40–200 nM.
contrast to significant absorbance change (ΔA660) for 30 nM Ag+, very little change of the absorbance change was observed upon exposure to other metal ions. Moreover, a distinct difference in the solution color can be observed for Ag+ and other metal ions. These results indicate that this method can be used to detect Ag+ with excellent selectivity.
References [1] C.Z. Lai, M.A. Fierke, R. Correa da Costa, J.A. Gladysz, A. Stein, P. Buhlmann, Highly selective detection of silver in the low ppt range with ion-selective electrodes based on ionophore-doped fluorous membranes, Anal. Chem. 82 (2010) 7634. [2] Morgan T P and Wood CM 2004 A relationship between gill silver accumulation and acute silver toxicity in the freshwater rainbow trout: support for the acute silver Biotic Ligand Model Environ. Toxicol. Chem. 231261. [3] M.K. Amini, M. Ghaedi, A. Rafia, I. Mohamadpoor-Baltork, K. Niknam, Silver selective electrodes based on methyl-2-pyridyl ketone oxime: phenyl-2-pyridyl ketone oxime and bis[2-(o-carboxythiophenoxy)methyl]-4-bromo-1-methoxybenzene carriers, Sensors Actuators B Chem. 96 (2003) 669. [4] S. Dadfarnia, A.M.H. Shabani, M. Gohari, Trace enrichment and determination of silver by immobilized DDTC microcolumn and flow injection atomic absorption spectrometry, Talanta 64 (2004) 682–687. [5] M. Krachler, C. Mohl, H. Emons, W. Shotyk, Analytical procedures for the determination of selected trace elements in peat and plant samples by inductively coupled plasma mass spectrometry, Spectrochim. Acta Part B 57 (2002) 1277. [6] R.P. Singh, E.P. Pambid, Selective separation of silver from waste solutions on chromium(III) hexacyanoferrate(III) ion exchanger, Analyst 115 (1990) 301. [7] X.H. Zhou, D.M. Kong, H.X. Shen, G-quadruplex-hemin DNAzyme-amplified colorimetric detection of Ag+ ion, Anal. Chim. Acta 678 (2010) 124. [8] C. Zhao, K.G. Qu, Y.J. Song, C. Xu, J.S. Ren, X.G. Qu, A reusable DNA single-walled carbon-nanotube-based fluorescent sensor for highly sensitive and selective detection of Ag+ and cysteine in aqueous solutions, Chem. Eur. J. 16 (2010) 8147. [9] L. Wang, J. Tian, H. Li, Y. Zhang, X. Sun, A novel single-labeled fluorescent oligonucleotide probe for silver(I) ion detection based on the inherent quenching ability of deoxyguanosines, Analyst 136 (2011) 891. [10] J. Lee, J. Park, H. Hee Lee, H. Park, H.I. Kim, W.J. Kim, Fluorescence switch for silver ion detection utilizing dimerization of DNA-Ag nanoclusters, Biosens. Bioelectron. 68 (2015) 642. [11] G. Xu, G. Wang, Y. Zhu, L. Chen, X. He, L. Wang, X. Zhang, Amplified and selective detection of Ag+ ions based on electrically contacted enzymes on duplex-like DNA scaffolds Biosens, Bioelectron. 59 (2014) 269. [12] S.T. Mensah, Y. Gonzalez, P. Calvo-Marzal, K.Y. Chumbimuni-Torres, Nanomolar detection limits of Cd2+, Ag+, and K+ using paper-strip ion-selective electrodes, Anal. Chem. 86 (2014) 7269. [13] Z. Lin, X. Li, H.B. Kraatz, Impedimetric immobilized DNA-based sensor for simultaneous detection of Pb2+, Ag+, and Hg2+, Anal. Chem. 83 (2011) 6896. [14] B. Li, Y. Du, S. Dong, DNA based gold nanoparticles colorimetric sensors for sensitive and selective detection of Ag(I) ions, Anal. Chim.Acta 644 (2009) 78. [15] S. Liu, J.Q. Tian, L. Wang, X.P. Sun, Highly sensitive and selective colorimetric detection of Ag(I) ion using 3,3′,5,5′,-tetramethylbenzidine (TMB) as an indicator, Sens.Actuators B-Chem. 165 (2012) 44. [16] Y. Song, W. Wei, X. Qu, Colorimetric biosensing using smart materials, Adv. Mater. 23 (2011) 4215. [17] X. Zhou, D. Kong, H. Shen, Ag+ and cysteine quantitation based on G-quadruplexhemin DNAzymes disruption by Ag+, Anal. Chem. 82 (2010) 789. [18] C. Lin, C. Yu, Y. Lin, W. Tseng, Colorimetric sensing of silver(I) and mercury(II) ions based on an assembly of Tween 20-stabilized gold nanoparticles, Anal. Chem. 82 (2010) 6830. [19] H. Huang, C. Qu, X. Liu, S. Huang, Z. Xu, B. Liao, Y. Zeng, P.K. Chu, Preparation of controllable core-shell gold nanoparticles and its application in detection of silver ions, ACS Appl. Mater. Interfaces 3 (2011) 183. [20] Z. Gao, K. Deng, X. Wang, M. Miró, D. Tang, High-resolution colorimetric assay for rapid visual readout of phosphatase activity based on gold/silver core/shell nanorod, ACS Appl. Mater. Interfaces 6 (2014) 18243. [21] Y.N. Ding, B.C. Yang, H. Liu, Z.X. Liu, X. Zhang, X.W. Zheng, Q.Y. Liu, FePt-Au ternary metallic nanoparticles with the enhanced peroxidase-like activity for ultrafast colorimetric detection of H2O2, Sensor Actuat B: Chem. 259 (2018) 775. [22] H. Liu, Y. Ding, B. Yang, Z. Liu, Q. Liu, X. Zhang, Colorimetric and ultrasensitive
3.4. Real sample detection To demonstrate the potential application of the method in environmental scenarios, river water samples from Beijing moat spiked with Ag+ ions were analyzed. It should be mentioned that the original river water was free of Ag+, as confirmed by ICP-MS analysis. Ag+spiked river water samples in the concentration range of 0–1 μM were measured using UV–vis spectroscopy (Fig. 3A). As shown in Fig. 3B, the colorimetric response change for river water samples from 40 to 200 nM gives a linear fit, and a minimum concentration of 1 nM for Ag+ in river water can be detected with the naked-eye. The applicability of the present method for detecting Ag+ in urine samples was evaluated. As shown in Table 1. It is shown that the measured values for different urine samples with known concentrations of Ag+ exhibited good recoveries of 95–100.36%. Therefore, the potential application of our colorimetric method in real environmental samples is promising. 4. Conclusion In conclusion, by taking advantage of specific C-Ag+-C coordination chemistry and the unique optical properties of MB, we have successfully developed a colorimetric method for simple and effective detection of Ag+ with a broad detection range (1 nM to 1 μM) and a low detection limit (1 nM). The advantages of this method lie in its simplicity and cost efficiency, which avoids the tedious synthesis of nanoparticles, and no further chemical modification of DNA is required, making the method more convenient and more readily adopted than other nanoparticle or chemically modified DNA-based approaches. We hope that this type of assay will be useful in remote districts, where highly sensitive assays without advanced instrumentation are highly desired. Table 1 Results of the detection of Ag+ in urine samples. Sample Sample Sample Sample Sample
1 2 3 4
Ag+ added (nM)
Ag+ measured (nM)
Recovery (%)
0 5 10 50
0 4.83 9.50 50.18
96.6 95.0 100.36
997
Microchemical Journal 147 (2019) 995–998
S. Xu, et al. detection of H2O2 based on Au/Co3O4-CeOx nanocomposites with enhanced peroxidase-like performance, Sensor Actuat B: Chem. 271 (2018) 336. [23] K. Wu, X. Zhao, M. Chen, H. Zhang, Z. Liu, X. Zhang, X. Zhu, Q. Liu, Synthesis of well-dispersed Fe3O4 nanoparticles loaded on montmorillonite and sensitive colorimetric detection of H2O2 based on its peroxidase-like activity, New J. Chem. 42
(2018) 9578. [24] Q. Liu, Y. Yang, H. Li, R. Zhu, Q. Shao, S. Yang, J. Xu, NiO nanoparticles modified with 5,10,15,20-tetrakis(4-carboxyl pheyl)-porphyrin: promising peroxidase mimetics for H2O2 and glucose detection, Biosens. Bioelectron. 64 (2015) 147.
998
Contents lists available at ScienceDirect
Microchemical Journal journal homepage: www.elsevier.com/locate/microc
Methylene blue-based distinguishing DNA conformation for colorimetric detection of silver ions☆
T
Song Xua, , Xiaojuan Chena, Xin Chena, Yong Liangb ⁎
a b
School of Environment and Chemical Engineering, Foshan University, Foshan 528000, China School of Chemistry and Environment, South China Normal University, Guangzhou 510631, China
ARTICLE INFO
ABSTRACT
Keywords: Silver ion Colorimetric Single-stranded Methylene blue C-Ag+-C formation
A highly sensitive colorimetric sensing strategy based on the interaction between methylene blue (MB) and Crich single-stranded DNA (ssDNA) (24C used here) has been developed for detection of Ag+. In the absence of target Ag+, the interaction between MB and 24C makes the color immediately change from blue to purple. However, specific C-Ag+-C pair forms when Ag+ ions are present in the aqueous solution containing 24C and MB, resulting in the desorption of MB from the surface of 24C into the solution. As a result, the color changes from purple to blue, and the absorbance values of MB at 660 and 605 nm gradually decrease. The detection limit can be as low as 1 nM, which satisfies the guideline concentration of Ag+ in drinking water set by the United States Environmental Protection Agency (EPA). The practical use of this method for Ag+ detection in river water samples is also demonstrated successfully.
1. Introduction Among biologically important metal ions, silver ion (Ag+) has always drawn considerable attention due to its antimicrobial and toxic activities. Ag+ at low concentration shows strong antimicrobial activity [1]. However, high concentrations of Ag+ exhibit serious biological effects on human health, such as urine silver excretion and blood silver (argyria), cardiac enlargement, growth retardation, and degenerative changes in the liver [2,3]. Therefore, it is vital to develop the sensing strategy of Ag+ with high sensitivity and selectivity. A variety of detection methods, such as atomic absorption spectrometry [4], inductively coupled plasma-mass spectroscopy [5], plasma atomic emission spectrometry [6], and fluorescence [7–10], electrochemistry [11–13], have been developed for the detection of Ag+. These methods have been successfully used to detect trace levels of Ag+, however, they generally require complicated protocols, sophisticated instruments, and skilled operators. Thus, such requirements largely limit practical applications of these methods, especially in resource-limited areas. Alternatively, colorimetric methods [14,15] have been widely used to detect Ag+ because they can be easily operated by less-trained personnel with an inexpensive spectrophotometer or even the bared eye [16–24]. Nevertheless, the methods usually involve complex synthesis of nanomaterials.
In this paper, we present a simple but effective colorimetric assay for Ag+ detection based on the specific interaction between methylene blue (MB) and C-rich single-stranded DNA (ssDNA) (here 24C). The specific interaction mainly relies on the sequence of ssDNA, in which more than 3 consecutive C bases are needed. The sequence and structure dual-dependent interaction mode inspires us to come up with the idea for Ag+ sensing. Without target Ag+, MB molecules are absorbed on the surface of 24C, leading to color change of MB from blue to purple. Whereas in the presence of target Ag+, the specific C-Ag+-C coordination impels MB absorbed on 24C surface to remove off, it returns to its own blue. Therefore, the C-Ag+-C coordination affects the interaction between MB and 24C, further affecting the colorimetric signals of MB. By taking advantage of diverse colorimetric signal induced by the interaction, highly sensitive and selective detection of Ag+ is realized. 2. Experimental section 2.1. Reagents and chemicals Methylene blue (MB), and trisodium citrate, ethylenediaminetetraacetic acid disodium salt dehydrate (EDTA), were purchased from Sigma-Aldrich. 5′-CCC CCC CCC CCC CCC CCC CCC CCC-3′ (24C) were
Selected papers from the XVI Hungarian – Italian Symposium on Spectrochemistry: Technological innovation for water science and sustainable aquatic biodiversity, 3-6th October 2018, Budapest. ⁎ Corresponding author. E-mail addresses: [email protected] (S. Xu), [email protected] (Y. Liang). ☆
https://doi.org/10.1016/j.microc.2019.04.019 Received 15 March 2019; Received in revised form 4 April 2019; Accepted 4 April 2019 Available online 05 April 2019 0026-265X/ © 2019 Elsevier B.V. All rights reserved.
Microchemical Journal 147 (2019) 995–998
S. Xu, et al.
Scheme 1. Mechanism of the interaction between MB and aptamer-based colorimetric probe for Ag+ detection.
Fig. 1. (A) Changes of absorption spectra after the addition of Ag+ with various concentrations ranging from 0 to 1 μM. (B) Linear calibration plot for Ag+ detection. Inset: Color change corresponding to different concentration of Ag+.
temperature. 3. Results and discussion 3.1. Detection mechanism The proposed mechanism of colorimetric probe for Ag+ detection based on the interaction between MB and aptamer-based is shown in Scheme 1. It is found that in the absence of target Ag+, MB can interact with cytosine (C)-rich single-stranded DNA (ssDNA) (24C), the solution color changes from blue to purple. However, in the presence of target Ag+, an interaction between MB and 24C occurs, which liberates MB into the solution. Thus, the solution color undergoes a change from purple to blue. Relying on C-Ag+-C formation-induced color change, the assay successfully quantifies Ag+ selectively and sensitively.
Fig. 2. Absorbance change of MB solution in the presence of different individual metal ions (the concentration of interfering metal ions was 100-fold higher than that of Ag+). Inset: the corresponding color of metal ion solution.
3.2. Analytical performances for Ag+ detection
Ultraviolet-visible (UV–vis) absorption spectrum measurement was carried out by an UV-2550 Spectrophotometer (Shimadzu Corporation).
Under the optimized conditions mentioned above, the linear response range of the assay was measured. As displayed in Fig. 1A, with the increase of the added Ag+, the absorption peak at 660 and 605 nm is gradually decreased. Fig. 1B shows a good linear relationship between the ΔA660 and the logarithmic value of Ag+ concentrations from 1 nM to 1 μM. Thus, it can be concluded that our colorimetric probe can be used for the quantitative determination of Ag+ and the limit of detection (LOD) is 1 nM with the naked-eye, which is much lower than the threshold value of silver (∼460 nM) in drinking water permitted by the United States Environmental Protection Agency (EPA).
2.3. The procedure of Ag+ detection
3.3. Specificity test
First, 10 μL of 100 μM 24C and 50 μL of 200 μM MB were mixed with 70 μLTE buffer (10 mM Tris, 1 mM EDTA, pH 7.7). Then, 5 μL of Ag+ standard solutions with different concentrations were added, respectively. The absorbance of the above solutions was measured at room
We also studied the selectivity of the assay for Ag+ sensing. Common metal ions including Cd2+, Hg2+, Pb2+, Cu2+, Sn4+, Ni2+, Fe3+, and Mn2+, each at a concentration of 3 μM, as interfering ions were tested using the standard procedure. As shown in Fig. 2, in
synthesized by Sangon Biotechnology Co. Ltd. (Shanghai, China). All other reagents were of analytical reagent grade and directly used without additional purification. Ultrapure water was provided by a Direct-Q3 system and used as a solvent in all experiments. 2.2. Instrumentation
996
Microchemical Journal 147 (2019) 995–998
S. Xu, et al.
Fig. 3. (A) UV–vis absorption spectra of MB solutions incubated with different concentrations of Ag+ in the presence of 100 μM aptamer. (B) The ΔA660 versus different Ag+ concentrations in the range of 40–200 nM.
contrast to significant absorbance change (ΔA660) for 30 nM Ag+, very little change of the absorbance change was observed upon exposure to other metal ions. Moreover, a distinct difference in the solution color can be observed for Ag+ and other metal ions. These results indicate that this method can be used to detect Ag+ with excellent selectivity.
References [1] C.Z. Lai, M.A. Fierke, R. Correa da Costa, J.A. Gladysz, A. Stein, P. Buhlmann, Highly selective detection of silver in the low ppt range with ion-selective electrodes based on ionophore-doped fluorous membranes, Anal. Chem. 82 (2010) 7634. [2] Morgan T P and Wood CM 2004 A relationship between gill silver accumulation and acute silver toxicity in the freshwater rainbow trout: support for the acute silver Biotic Ligand Model Environ. Toxicol. Chem. 231261. [3] M.K. Amini, M. Ghaedi, A. Rafia, I. Mohamadpoor-Baltork, K. Niknam, Silver selective electrodes based on methyl-2-pyridyl ketone oxime: phenyl-2-pyridyl ketone oxime and bis[2-(o-carboxythiophenoxy)methyl]-4-bromo-1-methoxybenzene carriers, Sensors Actuators B Chem. 96 (2003) 669. [4] S. Dadfarnia, A.M.H. Shabani, M. Gohari, Trace enrichment and determination of silver by immobilized DDTC microcolumn and flow injection atomic absorption spectrometry, Talanta 64 (2004) 682–687. [5] M. Krachler, C. Mohl, H. Emons, W. Shotyk, Analytical procedures for the determination of selected trace elements in peat and plant samples by inductively coupled plasma mass spectrometry, Spectrochim. Acta Part B 57 (2002) 1277. [6] R.P. Singh, E.P. Pambid, Selective separation of silver from waste solutions on chromium(III) hexacyanoferrate(III) ion exchanger, Analyst 115 (1990) 301. [7] X.H. Zhou, D.M. Kong, H.X. Shen, G-quadruplex-hemin DNAzyme-amplified colorimetric detection of Ag+ ion, Anal. Chim. Acta 678 (2010) 124. [8] C. Zhao, K.G. Qu, Y.J. Song, C. Xu, J.S. Ren, X.G. Qu, A reusable DNA single-walled carbon-nanotube-based fluorescent sensor for highly sensitive and selective detection of Ag+ and cysteine in aqueous solutions, Chem. Eur. J. 16 (2010) 8147. [9] L. Wang, J. Tian, H. Li, Y. Zhang, X. Sun, A novel single-labeled fluorescent oligonucleotide probe for silver(I) ion detection based on the inherent quenching ability of deoxyguanosines, Analyst 136 (2011) 891. [10] J. Lee, J. Park, H. Hee Lee, H. Park, H.I. Kim, W.J. Kim, Fluorescence switch for silver ion detection utilizing dimerization of DNA-Ag nanoclusters, Biosens. Bioelectron. 68 (2015) 642. [11] G. Xu, G. Wang, Y. Zhu, L. Chen, X. He, L. Wang, X. Zhang, Amplified and selective detection of Ag+ ions based on electrically contacted enzymes on duplex-like DNA scaffolds Biosens, Bioelectron. 59 (2014) 269. [12] S.T. Mensah, Y. Gonzalez, P. Calvo-Marzal, K.Y. Chumbimuni-Torres, Nanomolar detection limits of Cd2+, Ag+, and K+ using paper-strip ion-selective electrodes, Anal. Chem. 86 (2014) 7269. [13] Z. Lin, X. Li, H.B. Kraatz, Impedimetric immobilized DNA-based sensor for simultaneous detection of Pb2+, Ag+, and Hg2+, Anal. Chem. 83 (2011) 6896. [14] B. Li, Y. Du, S. Dong, DNA based gold nanoparticles colorimetric sensors for sensitive and selective detection of Ag(I) ions, Anal. Chim.Acta 644 (2009) 78. [15] S. Liu, J.Q. Tian, L. Wang, X.P. Sun, Highly sensitive and selective colorimetric detection of Ag(I) ion using 3,3′,5,5′,-tetramethylbenzidine (TMB) as an indicator, Sens.Actuators B-Chem. 165 (2012) 44. [16] Y. Song, W. Wei, X. Qu, Colorimetric biosensing using smart materials, Adv. Mater. 23 (2011) 4215. [17] X. Zhou, D. Kong, H. Shen, Ag+ and cysteine quantitation based on G-quadruplexhemin DNAzymes disruption by Ag+, Anal. Chem. 82 (2010) 789. [18] C. Lin, C. Yu, Y. Lin, W. Tseng, Colorimetric sensing of silver(I) and mercury(II) ions based on an assembly of Tween 20-stabilized gold nanoparticles, Anal. Chem. 82 (2010) 6830. [19] H. Huang, C. Qu, X. Liu, S. Huang, Z. Xu, B. Liao, Y. Zeng, P.K. Chu, Preparation of controllable core-shell gold nanoparticles and its application in detection of silver ions, ACS Appl. Mater. Interfaces 3 (2011) 183. [20] Z. Gao, K. Deng, X. Wang, M. Miró, D. Tang, High-resolution colorimetric assay for rapid visual readout of phosphatase activity based on gold/silver core/shell nanorod, ACS Appl. Mater. Interfaces 6 (2014) 18243. [21] Y.N. Ding, B.C. Yang, H. Liu, Z.X. Liu, X. Zhang, X.W. Zheng, Q.Y. Liu, FePt-Au ternary metallic nanoparticles with the enhanced peroxidase-like activity for ultrafast colorimetric detection of H2O2, Sensor Actuat B: Chem. 259 (2018) 775. [22] H. Liu, Y. Ding, B. Yang, Z. Liu, Q. Liu, X. Zhang, Colorimetric and ultrasensitive
3.4. Real sample detection To demonstrate the potential application of the method in environmental scenarios, river water samples from Beijing moat spiked with Ag+ ions were analyzed. It should be mentioned that the original river water was free of Ag+, as confirmed by ICP-MS analysis. Ag+spiked river water samples in the concentration range of 0–1 μM were measured using UV–vis spectroscopy (Fig. 3A). As shown in Fig. 3B, the colorimetric response change for river water samples from 40 to 200 nM gives a linear fit, and a minimum concentration of 1 nM for Ag+ in river water can be detected with the naked-eye. The applicability of the present method for detecting Ag+ in urine samples was evaluated. As shown in Table 1. It is shown that the measured values for different urine samples with known concentrations of Ag+ exhibited good recoveries of 95–100.36%. Therefore, the potential application of our colorimetric method in real environmental samples is promising. 4. Conclusion In conclusion, by taking advantage of specific C-Ag+-C coordination chemistry and the unique optical properties of MB, we have successfully developed a colorimetric method for simple and effective detection of Ag+ with a broad detection range (1 nM to 1 μM) and a low detection limit (1 nM). The advantages of this method lie in its simplicity and cost efficiency, which avoids the tedious synthesis of nanoparticles, and no further chemical modification of DNA is required, making the method more convenient and more readily adopted than other nanoparticle or chemically modified DNA-based approaches. We hope that this type of assay will be useful in remote districts, where highly sensitive assays without advanced instrumentation are highly desired. Table 1 Results of the detection of Ag+ in urine samples. Sample Sample Sample Sample Sample
1 2 3 4
Ag+ added (nM)
Ag+ measured (nM)
Recovery (%)
0 5 10 50
0 4.83 9.50 50.18
96.6 95.0 100.36
997
Microchemical Journal 147 (2019) 995–998
S. Xu, et al. detection of H2O2 based on Au/Co3O4-CeOx nanocomposites with enhanced peroxidase-like performance, Sensor Actuat B: Chem. 271 (2018) 336. [23] K. Wu, X. Zhao, M. Chen, H. Zhang, Z. Liu, X. Zhang, X. Zhu, Q. Liu, Synthesis of well-dispersed Fe3O4 nanoparticles loaded on montmorillonite and sensitive colorimetric detection of H2O2 based on its peroxidase-like activity, New J. Chem. 42
(2018) 9578. [24] Q. Liu, Y. Yang, H. Li, R. Zhu, Q. Shao, S. Yang, J. Xu, NiO nanoparticles modified with 5,10,15,20-tetrakis(4-carboxyl pheyl)-porphyrin: promising peroxidase mimetics for H2O2 and glucose detection, Biosens. Bioelectron. 64 (2015) 147.
998