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Communication

Cytosine-Rich Oligonucleotide and Electrochemically Reduced Graphene Oxide Nanocomposite for Ultrasensitive Electrochemical Ag+ Sensing

by
Nasir Abbas
†,
Seung Joo Jang
† and
Tae Hyun Kim
*
Department of Chemistry, Soonchunhyang University, Asan 31538, Republic of Korea
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Nanomaterials 2024, 14(9), 775; https://doi.org/10.3390/nano14090775
Submission received: 30 March 2024 / Revised: 19 April 2024 / Accepted: 26 April 2024 / Published: 29 April 2024
(This article belongs to the Special Issue Advanced Nanocomposites for Sensing Applications)
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Abstract

:
Silver ions (Ag+) are crucial in various fields, but pose environmental and health risks at high concentrations. This study presents a straightforward approach for the ultra-trace detection of Ag+, utilizing a composite of a cytosine-rich oligonucleotide (CRO) and an electrochemically reduced graphene oxide (ERGO). Initially, ERGO was synthesized on a glassy carbon electrode (GCE) through the reduction of graphene oxide (GO) via cyclic voltammetry. A methylene blue-tagged CRO (MB-CRO) was then anchored to the ERGO surface through π–π interactions, resulting in the formation of an MB-CRO-modified ERGO electrode (MB-CRO/ERGO-GCE). The interaction with Ag+ ions induced the formation of silver-mediated C-Ag+-C coordination, prompting the MB-CRO to adopt a hairpin structure. This conformational change led to the desorption of the MB-CRO from the ERGO-GCE, causing a variation in the redox current of the methylene blue associated with the MB-CRO. Electrochemical assays revealed that the sensor exhibits extraordinary sensitivity to Ag+ ions, with a linear detection range from 1 femtomolar (fM) to 100 nanomolars (nM) and a detection limit of 0.83 fM. Moreover, the sensor demonstrated high selectivity for Ag+ ions and several other benefits, including stability, reproducibility, and straightforward fabrication and operational procedures. Additionally, real sample analyses were performed using the modified electrode to detect Ag+ in tap and pond water samples, yielding satisfactory recovery rates.

1. Introduction

Silver ion (Ag+) is a precious metal ion valued for its rarity and applications in biomedicine [1], electronics [2], and various other fields [3,4,5,6]. At low concentrations, Ag+ exhibits beneficial properties such as anti-inflammatory [7], sterilizing [8], deodorizing [9], and wound-healing effects [10], and it is also known to inhibit certain bacteria [11], fungi, and viruses [12,13]. However, Ag+ can also pose environmental and health risks [14,15]. Silver is often found as an impurity in ores and can enter the environment through industrial waste [16,17,18]. Additionally, the widespread use of silver in industrial processes, including chemistry [19,20], medicine [21], photography [22], and electronics [23], leads to its discharge into the environment through industrial waste, often contaminating water and soil [24]. This environmental infiltration poses significant risks to plant growth [15] and ecological balance. Accumulation of Ag+ in animals and plants, coupled with its potential entry into the human body through the food chain, presents health hazards such as elevated urine silver excretion, argyria (a skin condition), cardiac enlargement, growth retardation, and liver damage [1,25,26]. Thus, the U.S Environmental Protection Agency (USEPA) and the World Health Organization (WHO) have set the toxic concentration standard for Ag+ at 1.6 nM. Additionally, the maximum permissible concentration of Ag+ in drinking water is specified as 0.93 μM and 0.36 μM, respectively. Furthermore, WHO limited the threshold for exposure of silver in water for fish and microorganisms to lower than 1.6 nmol L−1 [27,28]. Consequently, the detection of trace amounts of Ag+ is crucial for environmental protection and public health [29,30,31,32,33].
Conventional methods like atomic absorption spectrometry (AAS) [34,35,36], fluorescence [37,38], colorimetric [39], and inductively coupled plasma mass spectrometry (ICP-MS) offer high accuracy for Ag+ detection [40,41], but are often expensive and require complex instrumentation. These techniques typically require specialized equipment, high sample volumes, and lengthy processing times. While researchers have developed sensors for Ag+ detection using various spectroscopic techniques, these often involve complex design and synthesis procedures.
In recent years, electrochemical analysis technology has gained widespread adoption for detecting heavy metal ions [4,28], biomolecules [42], and food additives due to its high sensitivity and cost-effectiveness [43,44,45]. Consequently, numerous researchers have studied graphene composites to enhance sensor performance. Among these composites, reduced graphene oxide (RGO) has been considered as a promising material for improving the performance of electrochemical biosensors. RGO offers a large surface area, good biocompatibility, and excellent electrocatalytic activity, which are attributed to its abundant edge-plane-like defects and large surface area, facilitating rapid heterogeneous electron transfer [46,47,48,49]. Furthermore, RGO can readily bind with single-stranded DNA through π–π stacking. DNA aptamer-based electrochemical biosensors have emerged as particularly promising due to their advantages: enhanced sensitivity [50], rapid analysis [51], cost-effectiveness [52], straightforward fabrication [53], miniaturization potential [52], and suitability for on-site detection [54,55,56].
Previously, Prof. Han’s group suggested that aptasensors detect silver ions via probe packing density [57]. Their approach involved the use of cytosine-rich oligonucleotides (CRO) tagged with methylene blue, which were self-assembled onto the gold electrode surface via thiol groups from the aptamer’s 5′-terminal. In contrast, we propose methylene blue (MB)-tagged CRO modified on the electrochemically reduced graphene oxide (ERGO) deposition glassy carbon electrode (GCE) surface; this method does not require additional preparation of DNA such as thiolate. Additionally, single-stranded DNA can be reversibly absorbed simply by dipping the electrode in a DNA solution. To elaborate, Scheme 1 illustrates the fabrication process of the sensor and its Ag+ detection mechanism, demonstrating its simplicity, speed, and effectiveness. Briefly, ERGO is prepared and deposited onto a glassy carbon electrode through the direct reduction of GO using cyclic voltammetry (CV), following established protocols [58,59]. Subsequently, MB-CRO is immobilized onto the ERGO-modified GCE (ERGO-GCE) via π–π stacking [60,61]. The introduction of Ag+ prompts the MB-CRO on the ERGO-GCE, leading it to adopt a hairpin structure facilitated by a specific C-Ag+-C coordination [62,63,64]. This structural shift triggers the detachment of the MB-CRO from the ERGO surface, resulting in a marked alteration in the electrochemical signal of the MB tag. The sensor is characterized by its straightforward fabrication, ease of analysis, ultra-sensitivity, and high selectivity, making it a practical tool for Ag+ ion detection.

2. Materials and Methods

2.1. Materials

The cytosine-rich oligonucleotide aptamer (MB-CRO), with the sequence 5′-Methylene Blue-CCCCCCCCCCCCCCCCCCCCCCCC-3′ (24C) [65], was sourced from BIONEER Corporation (Daejeon, Republic of Korea). Graphite powder, phosphate buffer saline (PBS), Tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl), and potassium hexacyanoferrate (III) (K3[Fe(CN)6]) were procured from Sigma-Aldrich, Inc. (St. Louis, MO, USA). All chemicals employed were of analytical grade and utilized as received, without any further purification. The aqueous solutions were prepared using deionized water with a resistivity greater than 18 MΩcm, produced by a Millipore water purification system (MilliQ, Millipore Korea, Co., Ltd., Seoul, Republic of Korea).

2.2. Electrochemical Measurements

Electrochemical measurements were performed using a Model 660D electrochemical workstation (CH Instruments, Austin, TX, USA) with a conventional three-electrode cell at room temperature (25 °C). GCE, ERGO-GCE, and MB-CRO/ERGO-GCE served as working electrodes, with Ag/AgCl (3 M NaCl) as the reference electrode and a Pt wire as the counter electrode. All measurements, including cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS), were conducted in 10 mM phosphate-buffered saline (PBS) or 7.4 pH Tris buffer solution. CV experiments employed a potential scan from −0.2 to 0.6 V (vs. Ag/AgCl) at 10 mV/s with a 1 mV sampling interval. DPV utilized a scan range of 0.1 to −0.6 V (vs. Ag/AgCl), a pulse amplitude of 0.04 V, a pulse width of 0.2 s, and a pulse time of 0.5 s. EIS measurements were carried out in 10 mM Tris solution containing 5 mM [Fe(CN)6]4− at the formal potential of 0.222 V (vs. Ag/AgCl), with an AC voltage amplitude of 10 mV and a frequency range of 106 to 10−1 Hz. ZSimpWin 3.21 software (AMETEK. Inc., Oak Ridge, TN, USA) was used for EIS data fitting.

2.3. Fabrication of MB-CRO/ERGO-GCE

GO was produced via a modified Hummers method [66]. The resultant GO was ultrasonicated in 10 mM PBS buffer (pH 7.4) for 1 h, yielding a uniform yellow-brown solution (0.3 mg/mL in 10 mM PBS buffer, pH 7.4). Before constructing the ERGO-GCE, the GCE was polished to a mirror finish with alumina powders of 0.1, 0.3, and 0.05 µm, respectively, sonicated for 10 min in water and ethanol solution, and then rinsed with deionized water. The ERGO-GCE was fabricated by applying CV from 0.8 to −1.5 V vs. Ag/AgCl at a scan rate of 10 mV/s for three cycles in the GO solution (0.3 mg/mL in 10 mM PBS buffer, pH 7.4), using GCE as the working electrode. Finally, MB-CRO was immobilized onto the ERGO-GCE. The ERGO/GCE was incubated in 1 μM MB-CRO solution (10 mM Tris buffer, pH 7.4) for varying (10, 20, 30, 40, 50, 60, 70, and 80 min) incubation times. After incubation, the MB-CRO/ERGO-GCE was washed with buffer solution and dried at room temperature before use.

3. Results and Discussion

The fabrication process of MB-CRO/ERGO-GCE was characterized using CV and electrochemical impedance spectroscopy (EIS), with [Fe(CN)6]3− as a redox probe. In 0.1 M KCl containing 10 mM K3[Fe(CN)6], CV revealed a well-defined redox peak pair on the bare GCE (Figure 1A) with a peak-to-peak separation (ΔEp) of 84 mV. Modification with ERGO significantly increased the peak current (Ip) and decreased ΔEp (70 mV), indicating enhanced electron transfer due to ERGO’s conductivity. Immobilization of MB-CRO on ERGO-GCE resulted in a substantial decrease in Ip and a noticeable increase in ΔEp (205 mV). This suggests that the negatively charged MB-CRO acts as an insulator, thereby impeding electron transfer. These observations confirm the successful construction of the MB-CRO/ERGO-GCE. EIS further validated the modification process (Figure 1B). The Nyquist plot shows the charge transfer resistance (Rct) represented by the semicircle diameter at high frequencies. ERGO modification on the GCE resulted in a reduction in the Rct value from 206 Ω (bare GCE) to 189.2 Ω (ERGO-GCE), attributed to the catalytic effect of ERGO, which facilitates rapid electron transfer. Conversely, the attachment of MB-CRO to the ERGO-GCE surface caused a significant rise in Rct to 2156 Ω, attributable to the DNA structure’s low conductivity, which restricts electron movement. This further corroborates the successful fabrication of the MB-CRO/ERGO-GCE.
Furthermore, as shown in Figure S2, we calculated the active surface areas of both bare GCE and ERGO-GCE to validate the successful deposition of ERGO onto the electrode surface. The active surface areas were determined to be 0.059 cm2 for bare GCE and 0.063 cm2 for ERGO-GCE, respectively.
The potential of MB-CRO/ERGO-GCE as an electrochemical sensor for Ag+ detection was demonstrated through an assessment of EIS and DPV measurements upon Ag+ introduction. Figure 1C shows that increasing Ag+ concentrations corresponded to a decrease in Rct, with more pronounced decreases at higher concentrations. This suggests that Ag+ binding to MB-CRO on the electrode surface triggers a conformational change, leading to MB-CRO detachment and a decrease in the barrier-to-electron transfer. To exploit the MB tag for signal transduction, DPV measurements were performed in 10 mM Tris buffer (pH 7.4). Figure 1D shows the DPV curves, with the MB reduction peak at −0.35 V confirming MB-CRO immobilization. Upon Ag+ addition, a significant decrease in the MB peak current was observed. This can be attributed to the increased distance between the MB tag and the electrode surface due to Ag+-induced conformational changes and subsequent MB-CRO detachment. This experimental observation provides compelling evidence supporting the sensor’s capability to detect Ag+ ions.
Accumulation time for MB−CRO (1 µM) was 60 min, and incubation time for Ag+ detection was 5 min. To optimize the sensor’s performance, we investigated the effects of accumulation time, MB−CRO concentration for immobilization, and incubation time for the Ag+ sensing reaction on the voltammetric response in 10 mM Tris buffer (Figure 2). The sensor response increased with the MB−CRO immobilization time up to 60 min, indicating a gradual increase in immobilized MB−CRO (Figure 2A). Beyond 60 min, the response decreased, suggesting potential overcrowding or desorption. Therefore, 60 min was chosen as the optimal immobilization time. Similarly, the sensor response displayed a maximum at an MB−CRO concentration of 1 μM (Figure 2B). This suggests a balance between sufficient aptamer coverage and potential steric hindrance at higher concentrations. Moreover, the voltammetric response to Ag+ detection grew with longer incubation times, stabilizing at 5 min (Figure 2C). Therefore, a 5 min incubation period was deemed sufficient for the reaction.
The analytical performance of the MB-CRO/ERGO-GCE sensor for Ag+ detection was evaluated under optimized conditions, focusing on sensitivity, selectivity, reproducibility, and stability (Figure 3). In Figure 3A, DPV curves of the MB-CRO/ERGO-GCE are shown, with varying concentrations of Ag+ in 10 mM Tris buffer solution (pH 7.4). As the Ag+ concentration increased from 1 fM to 100 nM, the sensor’s peak current values gradually decreased. The calibration plot, illustrating the relationship between Ag+ concentrations and Ip, is depicted in the inset of Figure 3A. The plot reveals two distinct linear regions, each associated with different response characteristics. At lower concentrations, the sensor responded rapidly as Ag+ ions quickly interact with the electrode surface. At higher concentrations, the response slowed, resulting in two separate linear ranges due to this differential behavior. The first linear range, from 1 fM to 10 pM, is described by the regression equation of Ip (μA) = 0.26 Log[Ag+] + 1.2 (R2 = 0.98). The second linear range, from 10 pM to 100 nM, follows the regression equation of Ip (μA) = 0.12 Log[Ag+] − 0.44 (R2 = 0.99). Table 1 compares the performance of the MB-CRO/ERGO-GCE sensor with previously reported Ag+ sensors. The aptasensor we proposed exhibited an exceptional linear range and surpassed previously reported sensors in terms of sensitivity, achieving a remarkable limit of detection (LOD) of 0.83 fM. The sensor displayed excellent selectivity for Ag+ detection (Figure 3B). The peak current significantly changed only upon Ag+ addition (100 nM), while negligible responses were observed for other metal ions (Mn2+, Fe3+, Cu2+, Ni2+, Co2+, Mg2+) at a higher concentration (1 μM). The sensor also exhibited good reproducibility (Figure 3C). DPV responses from five independently fabricated electrodes showed minimal variation, indicating consistent sensor performance. Furthermore, the sensor demonstrated excellent long-term stability (Figure 3D). After 15 days of storage at room temperature, the peak current remained at 98.9% of its initial value, highlighting the sensor’s reliable performance.
To assess real-world applicability, the sensor’s performance was evaluated in tap water and pond water samples spiked with Ag+ (Table 2). Samples were prepared by diluting the real water with 10 mM Tris buffer (pH 7.4). The standard addition method was used to quantify Ag+. The results demonstrated good recovery rates and low relative standard deviation (RSD) values, indicating the sensor’s potential for Ag+ detection in real-world samples.

4. Conclusions

This work successfully demonstrates a novel and highly sensitive electrochemical aptasensor for Ag+ detection. The sensor leverages the specific interaction between MB-CRO and ERGO, achieving an ultra-high detection limit of 0.83 fM, surpassing current methods of Ag+ detection. Additionally, the sensor exhibits excellent selectivity for Ag+ ions, minimizing interference from other metal ions in real-world samples. The straightforward fabrication process and rapid analysis capabilities make the sensor readily deployable for on-site monitoring. Furthermore, the sensor demonstrates good reproducibility and stability, maintaining consistent performance across multiple fabrications and over time. The successful application of the sensor for Ag+ detection in real-world tap and pond water samples validates its potential for practical applications in environmental monitoring. This approach paves the way for developing highly sensitive and selective aptasensors for the detection of various environmental contaminants beyond Ag+. Future research will explore the sensor’s suitability for monitoring silver nanoparticle pollution and other areas of environmental and biological analysis.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/nano14090775/s1, Figure S1: Raman spectra of GO and ERGO; Figure S2. CV curves at various scan rates from 0.01 to 0.1 V/s at (A) bare GCE and (C) ERGO-GCE. (B) Linear plots of υ1/2 vs. redox peak currents (Ipa/Ipc) at (B) bare GCE and (D) ERGO-GCE in 5 mM [Fe(CN)6]3– in 0.1M KCl solution.

Author Contributions

Conceptualization, N.A. and T.H.K.; methodology, T.H.K.; software, N.A. and T.H.K.; validation N.A. and S.J.J.; formal analysis, N.A.; investigation, N.A.; resources, T.H.K.; data curation, N.A.; writing—original draft preparation, T.H.K.; writing—review and editing, T.H.K.; visualization, N.A., S.J.J. and T.H.K.; supervision, T.H.K.; project administration, T.H.K.; funding acquisition, T.H.K. All authors have read and agreed to the published version of the manuscript.

Funding

This work was financially supported by the National Research Foundation of Korea (NRF) grants (NRF-2020R1A2C1014918, NRF-2021R1A6A1A03039503) and the Korea Innovation Foundation grant (2023-DD-UP-0007) funded by the Ministry of Science and ICT (MSIT), as well as the Korea Basic Science Institute (National Research Facilities and Equipment Center) grant (2022R1A6C101B794) funded by the Ministry of Education (MOE). This work was also supported by the Soonchunhyang University research fund.

Data Availability Statement

Data are contained within the article and Supplementary Materials.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Fabrega, J.; Luoma, S.N.; Tyler, C.R.; Galloway, T.S.; Lead, J.R. Silver Nanoparticles: Behaviour and Effects in the Aquatic Environment. Environ. Int. 2011, 37, 517–531. [Google Scholar] [CrossRef] [PubMed]
  2. Bouafia, A.; Laouini, S.E.; Ahmed, A.S.A.; Soldatov, A.V.; Algarni, H.; Feng Chong, K.; Ali, G.A.M. The Recent Progress on Silver Nanoparticles: Synthesis and Electronic Applications. Nanomaterials 2021, 11, 2318. [Google Scholar] [CrossRef] [PubMed]
  3. Sang, S.; Yu, C.; Li, N.; Ji, Y.; Zhang, J. Characterization of a New Ag+-Selective Electrode with Lower Detection Limit. Int. J. Electrochem. Sci. 2012, 7, 3306–3313. [Google Scholar] [CrossRef]
  4. Cui, L.; Wu, J.; Ju, H. Electrochemical Sensing of Heavy Metal Ions with Inorganic, Organic and Bio-Materials. Biosens. Bioelectron. 2015, 63, 276–286. [Google Scholar] [CrossRef] [PubMed]
  5. Srivastava, N.K.; Majumder, C.B. Novel Biofiltration Methods for the Treatment of Heavy Metals from Industrial Wastewater. J. Hazard. Mater. 2008, 151, 1–8. [Google Scholar] [CrossRef]
  6. Vareda, J.P.; Valente, A.J.M.; Durães, L. Assessment of Heavy Metal Pollution from Anthropogenic Activities and Remediation Strategies: A Review. J. Environ. Manag. 2019, 246, 101–118. [Google Scholar] [CrossRef] [PubMed]
  7. Morozova, O.V. Silver Nanostructures: Limited Sensitivity of Detection, Toxicity and Anti-Inflammation Effects. Int. J. Mol. Sci. 2021, 22, 9928. [Google Scholar] [CrossRef]
  8. Chen, W.-C.; Ko, C.-Y.; Chang, K.-C.; Chen, C.-H. Influences of Processing and Sterilizing Strategies on Reduced Silver Nanoparticles in Poly(Vinyl Alcohol) Electrospun Membranes: Optimization and Preservation of Antibacterial Activity. Mater. Chem. Phys. 2020, 254, 123300. [Google Scholar] [CrossRef]
  9. Huang, P.; Wang, Z.; Shi, Y.; Zhang, R.; Feng, X.; Kan, J. Deodorizing Effects of Rosemary Extract on Silver Carp (Hypophthalmichthys Molitrix) and Determination of Its Deodorizing Components. J. Food Sci. 2022, 87, 636–650. [Google Scholar] [CrossRef] [PubMed]
  10. Rybka, M.; Mazurek, Ł.; Konop, M. Beneficial Effect of Wound Dressings Containing Silver and Silver Nanoparticles in Wound Healing—From Experimental Studies to Clinical Practice. Life 2023, 13, 69. [Google Scholar] [CrossRef] [PubMed]
  11. Jung, W.K.; Koo, H.C.; Kim, K.W.; Shin, S.; Kim, S.H.; Park, Y.H. Antibacterial Activity and Mechanism of Action of the Silver Ion in Staphylococcus Aureus and Escherichia Coli. Appl. Environ. Microbiol. 2008, 74, 2171–2178. [Google Scholar] [CrossRef] [PubMed]
  12. Choi, Y.; Kim, H.-A.; Kim, K.-W.; Lee, B.-T. Comparative Toxicity of Silver Nanoparticles and Silver Ions to Escherichia coli. J. Environ. Sci. 2018, 66, 50–60. [Google Scholar] [CrossRef] [PubMed]
  13. Caroli, S.; Forte, G.; Iamiceli, A.L.; Galoppi, B. Determination of Essential and Potentially Toxic Trace Elements in Honey by Inductively Coupled Plasma-Based Techniques. Talanta 1999, 50, 327–336. [Google Scholar] [CrossRef] [PubMed]
  14. Greulich, C.; Braun, D.; Peetsch, A.; Diendorf, J.; Siebers, B.; Epple, M.; Köller, M. The Toxic Effect of Silver Ions and Silver Nanoparticles towards Bacteria and Human Cells Occurs in the Same Concentration Range. RSC Adv. 2012, 2, 6981–6987. [Google Scholar] [CrossRef]
  15. Mikelova, R.; Baloun, J.; Petrlova, J.; Adam, V.; Havel, L.; Petrek, J.; Horna, A.; Kizek, R. Electrochemical Determination of Ag-Ions in Environment Waters and Their Action on Plant Embryos. Bioelectrochemistry 2007, 70, 508–518. [Google Scholar] [CrossRef] [PubMed]
  16. Lasko, C.L.; Hurst, M.P. An Investigation into the Use of Chitosan for the Removal of Soluble Silver from Industrial Wastewater. Environ. Sci. Technol. 1999, 33, 3622–3626. [Google Scholar] [CrossRef]
  17. Escudero, L.B.; Vanni, G.; Duarte, F.A.; Segger, T.; Dotto, G.L. Biosorption of Silver from Aqueous Solutions Using Wine Industry Wastes. Chem. Eng. Commun. 2018, 205, 325–337. [Google Scholar] [CrossRef]
  18. Wang, J.; Huang, C.P.; Pirestani, D. Interactions of Silver with Wastewater Constituents. Water Res. 2003, 37, 4444–4452. [Google Scholar] [CrossRef] [PubMed]
  19. Purcell, T.W.; Peters, J.J. Sources of Silver in the Environment. Environ. Toxic. Chem. 1998, 17, 539–546. [Google Scholar] [CrossRef]
  20. Millar, G.J.; Collins, M. Industrial Production of Formaldehyde Using Polycrystalline Silver Catalyst. Ind. Eng. Chem. Res. 2017, 56, 9247–9265. [Google Scholar] [CrossRef]
  21. Betts, H.D.; Whitehead, C.; Harris, H.H. Silver in Biology and Medicine: Opportunities for Metallomics Researchers. Metallomics 2021, 13, mfaa001. [Google Scholar] [CrossRef] [PubMed]
  22. Stempien, Z.; Rybicki, E.; Rybicki, T.; Lesnikowski, J. Inkjet-Printing Deposition of Silver Electro-Conductive Layers on Textile Substrates at Low Sintering Temperature by Using an Aqueous Silver Ions-Containing Ink for Textronic Applications. Sens. Actuators B Chem. 2016, 224, 714–725. [Google Scholar] [CrossRef]
  23. R., V.K.R.; K., V.A.; Karthik, P.S.; Singh, S.P. Conductive Silver Inks and Their Applications in Printed and Flexible Electronics. RSC Adv. 2015, 5, 77760–77790. [Google Scholar] [CrossRef]
  24. Courtois, P.; de Vaufleury, A.; Grosser, A.; Lors, C.; Vandenbulcke, F. Transfer of Sulfidized Silver from Silver Nanoparticles, in Sewage Sludge, to Plants and Primary Consumers in Agricultural Soil Environment. Sci. Total Environ. 2021, 777, 145900. [Google Scholar] [CrossRef]
  25. Puchkova, L.V.; Broggini, M.; Polishchuk, E.V.; Ilyechova, E.Y.; Polishchuk, R.S. Silver Ions as a Tool for Understanding Different Aspects of Copper Metabolism. Nutrients 2019, 11, 1364. [Google Scholar] [CrossRef] [PubMed]
  26. Singh, G.; Singh, A.; Satija, P.; Sharma, G.; Shilpy, S.; Singh, J.; Singh, J.; Singh, K.N.; Kaur, A. First Report of Silver Ion Recognition via a Silatrane-Based Receptor: Excellent Selectivity, Low Detection Limit and Good Applicability. New J. Chem. 2019, 43, 5525–5530. [Google Scholar] [CrossRef]
  27. Xiao, Z.; Meng, H.; Qin, X.; Sang, X.; Zhang, Y.; Yuan, Y. The Functionalization of Gold Nanoparticles as a Novel Platform for the Highly Efficient Electrochemical Detection of Silver Ions. Analyst 2021, 146, 597–604. [Google Scholar] [CrossRef]
  28. Wang, J.; Li, H.; Liao, W.; Liu, K.; Li, H.; Geioushy, R.A.; Tahawy, R.; Sayed, M.; Jiang, L.; Fu, J.; et al. Highly Selective and Sensitive Photoelectrochemical Detection of Silver Ions in Complex Industrial Wastewater. Sens. Actuators B Chem. 2024, 399, 134796. [Google Scholar] [CrossRef]
  29. Dai, F.; Xie, M.; Wang, Y.; Zhang, L.; Zhang, Z.; Lu, X. Synergistic Effect Improves the Response of Active Sites to Target Variations for Picomolar Detection of Silver Ions. Anal. Chem. 2022, 94, 10462–10469. [Google Scholar] [CrossRef]
  30. McGillicuddy, E.; Murray, I.; Kavanagh, S.; Morrison, L.; Fogarty, A.; Cormican, M.; Dockery, P.; Prendergast, M.; Rowan, N.; Morris, D. Silver Nanoparticles in the Environment: Sources, Detection and Ecotoxicology. Sci. Total Environ. 2017, 575, 231–246. [Google Scholar] [CrossRef]
  31. Ahamed, M.; AlSalhi, M.S.; Siddiqui, M.K.J. Silver Nanoparticle Applications and Human Health. Clin. Chim. Acta 2010, 411, 1841–1848. [Google Scholar] [CrossRef] [PubMed]
  32. Tian, Y.; Chen, Y.; Chen, M.; Song, Z.-L.; Xiong, B.; Zhang, X.-B. Peroxidase-like Au@Pt Nanozyme as an Integrated Nanosensor for Ag+ Detection by LSPR Spectroscopy. Talanta 2021, 221, 121627. [Google Scholar] [CrossRef] [PubMed]
  33. Liu, W.; Wu, Y.; Wang, C.; Li, H.C.; Wang, T.; Liao, C.Y.; Cui, L.; Zhou, Q.F.; Yan, B.; Jiang, G.B. Impact of Silver Nanoparticles on Human Cells: Effect of Particle Size. Nanotoxicology 2010, 4, 319–330. [Google Scholar] [CrossRef] [PubMed]
  34. Dadfarnia, S.; Haji Shabani, A.M.; Gohari, M. Trace Enrichment and Determination of Silver by Immobilized DDTC Microcolumn and Flow Injection Atomic Absorption Spectrometry. Talanta 2004, 64, 682–687. [Google Scholar] [CrossRef] [PubMed]
  35. Bermejo-Barrera, P.; Moreda-Piñeiro, A.; Bermejo-Barrera, A. Study of Chemical Modifiers for Direct Determination of Silver in Sea Water by ETA-AAS with Deuterium Background Correction. Talanta 1996, 43, 35–44. [Google Scholar] [CrossRef] [PubMed]
  36. Dittert, I.M.; Borges, D.L.G.; Welz, B.; Curtius, A.J.; Becker-Ross, H. Determination of Silver in Geological Samples Using High-Resolution Continuum Source Electrothermal Atomic Absorption Spectrometry and Direct Solid Sampling. Microchim. Acta 2009, 167, 21. [Google Scholar] [CrossRef]
  37. Cheng, X.-Q.; Dai, Z.-H.; Gao, H.-X.; Pan, Q.-S.; Kong, X.-J.; Shen, F.-F.; Wu, S. Dual-Readout Assay for Determination of Ag+ and Cu2+ Based on in Situ Fluorogenic and Chromogenic Reaction between Dopamine and Naphthoresorcin. Microchem. J. 2024, 196, 109591. [Google Scholar] [CrossRef]
  38. Hao, C.; Wei, J.; Zong, S.; Wang, Z.; Wang, H.; Cui, Y. Highly Sensitive and Specific Detection of Silver Ions Using a Dual-Color Fluorescence Co-Localization Strategy. Analyst 2023, 148, 675–682. [Google Scholar] [CrossRef] [PubMed]
  39. Li, J.; Xi, H.; Kong, C.; Liu, Q.; Chen, Z. “Aggregation-to-Deaggregation” Colorimetric Signal Amplification Strategy for Ag+ Detection at the Femtomolar Level with Dark-Field Microscope Observation. Anal. Chem. 2018, 90, 11723–11727. [Google Scholar] [CrossRef] [PubMed]
  40. Ndung’u, K.; Ranville, M.A.; Franks, R.P.; Flegal, A.R. On-Line Determination of Silver in Natural Waters by Inductively-Coupled Plasma Mass Spectrometry: Influence of Organic Matter. Mar. Chem. 2006, 98, 109–120. [Google Scholar] [CrossRef]
  41. Jingyu, H.; Zheng, L.; Haizhou, W. Determination of Trace Silver in Superalloys and Steels by Inductively Coupled Plasma-Mass Spectrometry. Anal. Chim. Acta 2002, 451, 329–335. [Google Scholar] [CrossRef]
  42. Suhito, I.R.; Koo, K.-M.; Kim, T.-H. Recent Advances in Electrochemical Sensors for the Detection of Biomolecules and Whole Cells. Biomedicines 2021, 9, 15. [Google Scholar] [CrossRef] [PubMed]
  43. Li, S.; Zhang, C.; Wang, S.; Liu, Q.; Feng, H.; Ma, X.; Guo, J. Electrochemical Microfluidics Techniques for Heavy Metal Ion Detection. Analyst 2018, 143, 4230–4246. [Google Scholar] [CrossRef] [PubMed]
  44. Li, J.; Liu, S.; Mao, X.; Gao, P.; Yan, Z. Trace Determination of Rare Earths by Adsorption Voltammetry at a Carbon Paste Electrode. J. Electroanal. Chem. 2004, 561, 137–142. [Google Scholar] [CrossRef]
  45. Li, Z.; Zhu, M. Detection of Pollutants in Water Bodies: Electrochemical Detection or Photo-Electrochemical Detection? Chem. Commun. 2020, 56, 14541–14552. [Google Scholar] [CrossRef] [PubMed]
  46. Liu, Y.; Yu, D.; Zeng, C.; Miao, Z.; Dai, L. Biocompatible Graphene Oxide-Based Glucose Biosensors. Langmuir 2010, 26, 6158–6160. [Google Scholar] [CrossRef] [PubMed]
  47. Shan, C.; Yang, H.; Song, J.; Han, D.; Ivaska, A.; Niu, L. Direct Electrochemistry of Glucose Oxidase and Biosensing for Glucose Based on Graphene. Anal. Chem. 2009, 81, 2378–2382. [Google Scholar] [CrossRef] [PubMed]
  48. Mohanty, N.; Berry, V. Graphene-Based Single-Bacterium Resolution Biodevice and DNA Transistor: Interfacing Graphene Derivatives with Nanoscale and Microscale Biocomponents. Nano Lett. 2008, 8, 4469–4476. [Google Scholar] [CrossRef] [PubMed]
  49. Sun, X.; Liu, Z.; Welsher, K.; Robinson, J.T.; Goodwin, A.; Zaric, S.; Dai, H. Nano-Graphene Oxide for Cellular Imaging and Drug Delivery. Nano Res. 2008, 1, 203–212. [Google Scholar] [CrossRef] [PubMed]
  50. Kim, Y.S.; Chung, J.; Song, M.Y.; Jurng, J.; Kim, B.C. Aptamer Cocktails: Enhancement of Sensing Signals Compared to Single Use of Aptamers for Detection of Bacteria. Biosens. Bioelectron. 2014, 54, 195–198. [Google Scholar] [CrossRef] [PubMed]
  51. Abrego-Martinez, J.C.; Jafari, M.; Chergui, S.; Pavel, C.; Che, D.; Siaj, M. Aptamer-Based Electrochemical Biosensor for Rapid Detection of SARS-CoV-2: Nanoscale Electrode-Aptamer-SARS-CoV-2 Imaging by Photo-Induced Force Microscopy. Biosens. Bioelectron. 2022, 195, 113595. [Google Scholar] [CrossRef] [PubMed]
  52. Bosco, A.; Ambrosetti, E.; Mavri, J.; Capaldo, P.; Casalis, L. Miniaturized Aptamer-Based Assays for Protein Detection. Chemosensors 2016, 4, 18. [Google Scholar] [CrossRef]
  53. Jang, S.J.; Kim, T.H. Triple Multivalent Aptamers within DNA Tetrahedron on Reduced Graphene Oxide Electrode: Unlocking Enhanced Sensitivity and Accelerated Reactions in Electrochemical Sensing. Biosens. Bioelectron. 2024, 249, 116039. [Google Scholar] [CrossRef] [PubMed]
  54. Raoof, J.B.; Ojani, R.; Ebrahimi, M.; Hamidi-Asl, E. Developing a Nano-Biosensor for DNA Hybridization Using a New Electroactive Label. Chin. J. Chem. 2011, 29, 2541–2551. [Google Scholar] [CrossRef]
  55. Jiao, L.; Xu, W.; Wu, Y.; Yan, H.; Gu, W.; Du, D.; Lin, Y.; Zhu, C. Single-Atom Catalysts Boost Signal Amplification for Biosensing. Chem. Soc. Rev. 2021, 50, 750–765. [Google Scholar] [CrossRef] [PubMed]
  56. Yan, G.; Wang, Y.; He, X.; Wang, K.; Su, J.; Chen, Z.; Qing, Z. A Highly Sensitive Electrochemical Assay for Silver Ion Detection Based on Un-Labeled C-Rich ssDNA Probe and Controlled Assembly of MWCNTs. Talanta 2012, 94, 178–183. [Google Scholar] [CrossRef]
  57. Kim, K.; Bae, J.H.; Han, D. Oligonucleotide-Based Reusable Electrochemical Silver(I) Sensor and Its Optimization via Probe Packing Density. ACS Omega 2021, 6, 10801–10806. [Google Scholar] [CrossRef] [PubMed]
  58. Lee, C.-S.; Yu, S.; Kim, T. One-Step Electrochemical Fabrication of Reduced Graphene Oxide/Gold Nanoparticles Nanocomposite-Modified Electrode for Simultaneous Detection of Dopamine, Ascorbic Acid, and Uric Acid. Nanomaterials 2017, 8, 17. [Google Scholar] [CrossRef] [PubMed]
  59. Zhang, D.; Ouyang, X.; Ma, J.; Li, L.; Zhang, Y. Electrochemical Behavior and Voltammetric Determination of Curcumin at Electrochemically Reduced Graphene Oxide Modified Glassy Carbon Electrode. Electroanalysis 2016, 28, 749–756. [Google Scholar] [CrossRef]
  60. Liu, B.; Salgado, S.; Maheshwari, V.; Liu, J. DNA Adsorbed on Graphene and Graphene Oxide: Fundamental Interactions, Desorption and Applications. Curr. Opin. Colloid Interface Sci. 2016, 26, 41–49. [Google Scholar] [CrossRef]
  61. Yang, D.; Gao, S.; Fang, Y.; Lin, X.; Jin, X.; Wang, X.; Ke, L.; Shi, K. The π–π Stacking-Guided Supramolecular Self-Assembly of Nanomedicine for Effective Delivery of Antineoplastic Therapies. Nanomedicine 2018, 13, 3159–3177. [Google Scholar] [CrossRef] [PubMed]
  62. Li, Y.; Yuan, J.; Xu, Z. A Sensitive Fluorescence Biosensor for Silver Ions (Ag+) Detection Based on C-Ag+-C Structure and Exonuclease III-Assisted Dual-Recycling Amplification. J. Anal. Methods Chem. 2019, 2019, 3712032. [Google Scholar] [CrossRef] [PubMed]
  63. Ono, A.; Torigoe, H.; Tanaka, Y.; Okamoto, I. Binding of Metal Ions by Pyrimidine Base Pairs in DNA Duplexes. Chem. Soc. Rev. 2011, 40, 5855. [Google Scholar] [CrossRef] [PubMed]
  64. Ono, A.; Cao, S.; Togashi, H.; Tashiro, M.; Fujimoto, T.; Machinami, T.; Oda, S.; Miyake, Y.; Okamoto, I.; Tanaka, Y. Specific Interactions between Silver(i) Ions and Cytosine–Cytosine Pairs in DNA Duplexes. Chem. Commun. 2008, 39, 4825–4827. [Google Scholar] [CrossRef] [PubMed]
  65. Xu, S.; Chen, X.; Chen, X.; Liang, Y. Methylene Blue-Based Distinguishing DNA Conformation for Colorimetric Detection of Silver Ions. Microchem. J. 2019, 147, 995–998. [Google Scholar] [CrossRef]
  66. Zaaba, N.I.; Foo, K.L.; Hashim, U.; Tan, S.J.; Liu, W.-W.; Voon, C.H. Synthesis of Graphene Oxide Using Modified Hummers Method: Solvent Influence. Procedia Eng. 2017, 184, 469–477. [Google Scholar] [CrossRef]
  67. Fu, L.; Wang, A.; Xie, K.; Zhu, J.; Chen, F.; Wang, H.; Zhang, H.; Su, W.; Wang, Z.; Zhou, C.; et al. Electrochemical Detection of Silver Ions by Using Sulfur Quantum Dots Modified Gold Electrode. Sens. Actuators B Chem. 2020, 304, 127390. [Google Scholar] [CrossRef]
  68. Wasiewska, L.A.; Seymour, I.; Patella, B.; Inguanta, R.; Burgess, C.M.; Duffy, G.; O’Riordan, A. Reagent Free Electrochemical-Based Detection of Silver Ions at Interdigitated Microelectrodes Using in-Situ pH Control. Sens. Actuators B Chem. 2021, 333, 129531. [Google Scholar] [CrossRef]
  69. Zhang, C.; Yi, Y.; Zhou, Y.; Zhou, R.; Zhu, G. Homogeneous Electroanalysis Coupled with Colorimetry Dual-Mode Sensing of Silver Ion in Water Based on Target-Inhibited Peroxidase Activity of Pt@ZIF-8 Nanozyme. Microchem. J. 2024, 197, 109839. [Google Scholar] [CrossRef]
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Scheme 1. Fabrication and Ag+ detection mechanism of the MB-CRO/ERGO-GCE aptasensor.
Scheme 1. Fabrication and Ag+ detection mechanism of the MB-CRO/ERGO-GCE aptasensor.
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Figure 1. (A) CV curves for GCE, ERGO−GCE, and MB−CRO/ERGO−GCE obtained at a scan rate of 10 mV/s in 0.1 M KCl containing 10 mM [Fe(CN)6]3−. (B) Nyquist plots representing the electrochemical impedance of GCE, ERGO−GCE, and MB−CRO/ERGO−GCE in 10 mM Tris buffer with 10 mM [Fe(CN)6]3−. (C) EIS Nyquist plots of MB−CRO/ERGO−GCE upon exposure to varying Ag+ concentrations (0 M, 1 fM, 1 pM, 1 nM, and 1 µM) in 10 mM Tris buffer. (D) Differential pulse voltammograms (DPV) of MB−CRO/ERGO−GCE in the absence and presence of 100 nM Ag+ in 10 mM Tris buffer (pH 7.4).
Figure 1. (A) CV curves for GCE, ERGO−GCE, and MB−CRO/ERGO−GCE obtained at a scan rate of 10 mV/s in 0.1 M KCl containing 10 mM [Fe(CN)6]3−. (B) Nyquist plots representing the electrochemical impedance of GCE, ERGO−GCE, and MB−CRO/ERGO−GCE in 10 mM Tris buffer with 10 mM [Fe(CN)6]3−. (C) EIS Nyquist plots of MB−CRO/ERGO−GCE upon exposure to varying Ag+ concentrations (0 M, 1 fM, 1 pM, 1 nM, and 1 µM) in 10 mM Tris buffer. (D) Differential pulse voltammograms (DPV) of MB−CRO/ERGO−GCE in the absence and presence of 100 nM Ag+ in 10 mM Tris buffer (pH 7.4).
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Figure 2. (A) Effect of MB-CRO immobilization time on the sensor response ([MB-CRO] = 1 μM). (B) Effect of MB-CRO concentration for immobilization on the sensor response (MB-CRO accumulation time = 60 min). (C) Effect of Ag+ incubation time on the sensor response ([MB-CRO] = 1 μM MB-CRO, [Ag+] = 1μM, MB-CRO accumulation time = 60 min).
Figure 2. (A) Effect of MB-CRO immobilization time on the sensor response ([MB-CRO] = 1 μM). (B) Effect of MB-CRO concentration for immobilization on the sensor response (MB-CRO accumulation time = 60 min). (C) Effect of Ag+ incubation time on the sensor response ([MB-CRO] = 1 μM MB-CRO, [Ag+] = 1μM, MB-CRO accumulation time = 60 min).
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Figure 3. (A) DPV responses upon exposure to increasing Ag+ concentrations (1 fM–100 nM) in 10 mM Tris buffer. Inset: calibration plot showing the linear relationship between peak current (ΔIp) and Ag+ concentration (log scale). (B) DPV responses in the presence of 100 nM Ag+ and 1 μM of various potentially interfering metal ions (Mn2+, Fe3+, Cu2+, Ni2+, Co2+, Mg2+). (C) Reproducibility of sensor response for five independently fabricated electrodes. (D) Sensor stability over 15 days in 10 mM Tris buffer.
Figure 3. (A) DPV responses upon exposure to increasing Ag+ concentrations (1 fM–100 nM) in 10 mM Tris buffer. Inset: calibration plot showing the linear relationship between peak current (ΔIp) and Ag+ concentration (log scale). (B) DPV responses in the presence of 100 nM Ag+ and 1 μM of various potentially interfering metal ions (Mn2+, Fe3+, Cu2+, Ni2+, Co2+, Mg2+). (C) Reproducibility of sensor response for five independently fabricated electrodes. (D) Sensor stability over 15 days in 10 mM Tris buffer.
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Table 1. Comparison of Ag+ sensor performance.
Table 1. Comparison of Ag+ sensor performance.
MaterialsTechniqueLinear RangeLODRef.
BiOI NSsPEC0–300 μM0.21 μM[28]
SQDs/AuDPV0.1 nM–3 μM71 pM[67]
Au-IDASWV0.25 nM~2 nM106 nM[68]
CPM-PtUV-vis0.5~10 pM1.1 pM[29]
Oligonucleotide-Based Au ElectrodeDPV10–200 nM10 nM[57]
Pt@ZIF-8 nanozymeColorimetry0.1–1000.0 nM0.034 nM[69]
MB-CRO/ERGO-GCEDPV1 fM~100 nM0.83 fMThis work
Table 2. Detection of Ag+ concentrations in real samples using MB-CRO/ERGO-GCE (n = 3).
Table 2. Detection of Ag+ concentrations in real samples using MB-CRO/ERGO-GCE (n = 3).
SamplesAddedFoundRecovery (%)RSD (%)
Tap Water100 fM98.4 fM98.43.61
100 pM98.6 pM98.61.74
100 nM97.7 nM97.7135
Pond Water100 fM99.4 fM99.43.15
100 pM97.6 pM97.62.48
100 nM98.1 nM98.11.78
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Abbas, N.; Jang, S.J.; Kim, T.H. Cytosine-Rich Oligonucleotide and Electrochemically Reduced Graphene Oxide Nanocomposite for Ultrasensitive Electrochemical Ag+ Sensing. Nanomaterials 2024, 14, 775. https://doi.org/10.3390/nano14090775

AMA Style

Abbas N, Jang SJ, Kim TH. Cytosine-Rich Oligonucleotide and Electrochemically Reduced Graphene Oxide Nanocomposite for Ultrasensitive Electrochemical Ag+ Sensing. Nanomaterials. 2024; 14(9):775. https://doi.org/10.3390/nano14090775

Chicago/Turabian Style

Abbas, Nasir, Seung Joo Jang, and Tae Hyun Kim. 2024. "Cytosine-Rich Oligonucleotide and Electrochemically Reduced Graphene Oxide Nanocomposite for Ultrasensitive Electrochemical Ag+ Sensing" Nanomaterials 14, no. 9: 775. https://doi.org/10.3390/nano14090775

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