High-sensitivity detection of silver ions using oligonucleotide-immobilized oscillator

Carbon Dots-Based Fluorescence Assay for the Facile and Reliable Detection of Ag+ in Natural Water and Serum Samples

In this report, red-emissive carbon dots (C-dots) were facilely prepared from o-phenylenediamine via microwave-assisted hydrothermal treatment. The C-dots demonstrated excitation wavelength-independent emission with maximums at 621 nm that could be effectively quenched by Ag⁺ via static quenching. This phenomenon was exploited to establish a sensitive fluorescence assay with a low detection limit (0.37 μM) and wide linear range (0-50 μM). In addition, this assay demonstrated excellent selectivity toward Ag⁺, free from the interference of 16 commonly seen metal ions. Most importantly, the assay demonstrated high reliability toward samples in deionized water, mineral water, lake water, and serum, which could indicate potential applications for Ag⁺ monitoring in complicated natural and biological environments.

A review on silver-mediated DNA base pairs: methodology and application

The investigation of the interaction between metal ions and DNA has always attracted much attention in the fields of bioinorganic chemistry, supramolecular coordination chemistry, and DNA nanotechnology. Its mode of action can be simply divided into two aspects. On the one hand, it is non-specific electrostatic adsorption, mainly including Na⁺, K⁺, Mg²⁺, Ca²⁺ and other physiologically regulating ions; on the other hand, it is specific covalent binding, such as Pt²⁺, Hg²⁺, Ag⁺ and other heavy metal ions. This article focuses on the mechanism of action between Ag⁺ and DNA mismatch pair C-C, and summarizes its main characterization methods and various applications. It aims to provide a certain reference for the field of biological devices. With the development of cryo-electron microscopy and liquidcell TEM, the structure of C-Ag⁺-C is expected to be further characterized, which will be more widely used.

Fluorescence Anisotropy Reduction of An Allosteric G-Rich Oligonucleotide for Specific Silver Ion and Cysteine Detection Based on the G-Ag+-G Base Pair

Silver is a common heavy metal, and the detection of silver ion (Ag⁺) is of great importance because of its wide application and hazardous effect on the environment and human health. However, it is a great challenge to produce a large fluorescence anisotropy (FA) change for small molecules (e.g, Ag⁺). Herein, we describe a novel fluorescence anisotropy reduction approach for the sensitive and specific detection of Ag⁺. The feasibility of this method is demonstrated through screening a number of guanine-rich oligonucleotide probes. By selectively labeling the oligonucleotides with a single fluorophore tetramethylrhodamine (TMR), the reduction in FA response is associated with the conformation change from the unfolded to a hairpin-like folded structure by inducing formation of the intermolecular G-Ag⁺-G base pair, which diminishes the interaction between guanine and TMR by photoinduced electron transfer (PET). The change in FA allows the selective detection of Ag⁺ at a concentration as low as 0.5 nM with a dynamic range from 2.0 to 100 nM. The interference from the other 14 metal ions with a 100-fold even to a 1000-fold excess amount is negligible. This simple and cost-effective probe was further explored to determine cysteine (Cys) based on competing with a guanine-rich oligonucelotide for Ag⁺-binding.

L-Aspartic Acid Capped CdS Quantum Dots as a High Performance Fluorescence Assay for Sliver Ions (I) Detection

A new high performance fluorescence assay for detection of Ag+ based on CdS quantum dots (QDs) using L-Aspartic acid (L-Asp) as a stabilizer was proposed in this work. The CdS quantum dots conjugation with L-Aspartic acid (L-Asp@CdS QDs) were successfully synthesized via a simple hydrothermal process. The QDs have a fluorescence emission band maximum at 595 nm with a quantum yield of 11%. The obtained CdS QDs exhibit a particle size of 1.63 ± 0.28 nm and look like quantum dot flowers. Basically, the fluorescence intensity of L-Asp@CdS QDs can be enhanced only upon addition of Ag+ and a redshift in the fluorescence spectrum was observed. Under optimum conditions, the fluorescence enhancement of L-Asp@CdS QDs appeared to exhibit a good linear relationship in between 100-7000 nM (R2 = 0.9945) with the Ag+ concentration, with a detection limit of 39 nM. The results indicated that the L-Asp@CdS QDs were well used in detection for Ag+ as fluorescence probe in aqueous solution with high sensitivity and selectivity. Moreover, the sensing system has been applied in detection Ag+ in real water samples. The recovery test results were 98.6%~113%, and relative standard deviation (n = 5) is less than 3.6%, which was satisfactory.

Fabrication of a nanomaterial-based fluorescence sensor constructed from ligand capped CdTe quantum dots for ultrasensitive and rapid detection of silver ions in aqueous samples

In this study, CdTe QDs were prepared in aqueous medium and then capped with a synthetic heterocycle ligand (CdTe/L QDs) via surface modification method. Characterization of synthesized CdTe/L QDs was carried out through various analytical techniques including fluorescence spectroscopy, transmission electron microscopy (TEM), UV-Vis spectrophotometry, thermo-gravimetric (TG) analysis and Fourier transform infrared (FTIR). The fluorescence intensity of the CdTe/L QDs at 520 nm (excitation at 380 nm) was selectively quenched in the presence of trace amounts of silver ions. CdTe/L QDs were utilized as an ultrasensitive and selective fluorescent sensor for determination of trace concentrations of silver ions with a detection limit of 6.12 ± 0.11 × 10^-10 mol L^-1 and a linear range of 2.04 ± 0.10 × 10^-9 mol L^-1-3.63 ± 0.12 × 10^-7 mol L^-1. The fabricated optical sensor was also used for the measurement of silver ions in real water samples which yielded satisfactory analytical results. These results were also evaluated with inductively coupled plasma emission spectroscopy (ICP-OES). This study shows that CdTe/L QDs could have potential applications in selective and sensitive analysis of different water samples for detection of silver ions.

Extremely sensitive and wide-range silver ion detection via assessing the integrated surface potential of a DNA-capped gold nanoparticle

With the rapid development of nanotechnology and its associated waste stream, public concern is growing over the potential toxicity exposure to heavy metal ions poses to the human body and the environment. Herein, we report an extremely sensitive Kelvin probe force microscopy (KPFM)-based platform for detecting nanotoxic materials (e.g. Ag⁺) accomplished by probing the integrated surface potential differences of a single gold nanoparticle on which an interaction between probe DNA and target DNA occurs. This interaction can amplify the surface potential of the nanoparticle owing to the coordination bond mediated by Ag⁺ (cytosine-Ag⁺-cytosine base pairs). Interestingly, compared with conventional methods, this platform is capable of extremely sensitive Ag⁺ detection (∼1 fM) in a remarkably wide-range (1 fM to 1 μM). Furthermore, this platform enables Ag⁺ detection in a practical sample (general drinking water), and this KPFM-based technique may have the potential to detect other toxic heavy metal ions and single nucleotide polymorphisms by designing specific DNA sequences.

One-pot synthesis of dual carbon dots using only an N and S co-existed dopant for fluorescence detection of Ag. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2019;208:162-171. [PMID: 30312843 DOI: 10.1016/j.saa.2018.10.004]

Luminescent carbon-based nanoparticles, named often as carbon dots (CDs), were synthesized from citric acid (CA) and guanidine thiocyanate (GITC) via an N and S co-doped hydrothermal procedure. In the present structure characterization, N and S elements could be sufficiently doped by means of the heteroatom or the functional groups bonded on the surface of CDs. The as-prepared CDs solution showed blue color fluorescence under ultraviolet excitation, yet the PL spectra exhibited a repetitive emission process from excitation-independent to excitation-dependent. In view of the triexponential feature of fluorescence lifetimes of CDs, one possibility was proposed to be co-existence of two types of CDs with different surface states. Additionally, the as-prepared CDs were used as a sensing probe for the detection of Ag⁺ taking into consideration of the possible interactions between Ag⁺ and various fluorophores attached to the CD surface. As expected, the changes of fluorescence intensities were linearly proportional to the different concentration ranges of Ag⁺, which suggests the complex nature of the quenching mechanism. And for the first time, the SCN group was found to accelerate the quenching of CDs towards Ag⁺, promising a new approach for efficient detection of Ag⁺ for the application in industrial pollutants.

Fluorescent Sensors for the Detection of Heavy Metal Ions in Aqueous Media

Due to the risks that water contamination implies for human health and environmental protection, monitoring the quality of water is a major concern of the present era. Therefore, in recent years several efforts have been dedicated to the development of fast, sensitive, and selective sensors for the detection of heavy metal ions. In particular, fluorescent sensors have gained in popularity due to their interesting features, such as high specificity, sensitivity, and reversibility. Thus, this review is devoted to the recent advances in fluorescent sensors for the monitoring of these contaminants, and special focus is placed on those devices based on fluorescent aptasensors, quantum dots, and organic dyes.

Novel double layer film composed of reduced graphene oxide and Rose Bengal dye: design, fabrication and evaluation as an efficient chemosensor for silver(i) detection

A novel silver-chemosensor fabricated with reduced graphene oxide and Rose Bengal (RB) based on the interaction of Ag⁺ and RB.

A microcantilever-based silver ion sensor using DNA-functionalized gold nanoparticles as a mass amplifier

Silver ions have been used to sterilize many products, however, it has recently been demonstrated that silver ions can be toxic. This toxicity has been studied over many years with the lethal concentration at 10 μM. Silver ions can accumulate through the food chain, causing serious health problems in many species. Hence, there is a need for a commercially available silver ion sensor, with high detection sensitivity. In this work, we develop an ultra-sensitive silver ion sensor platform, using cytosine based DNA and gold nanoparticles as the mass amplifier. We achieve a lower detection limit for silver ions of 10 pM; this detection limit is one million times lower than the toxic concentration. Using our sensor platform we examine highly selective characteristics of other typical ions in water from natural sources. Furthermore, our sensor platform is able to detect silver ions in a real practical sample of commercially available drinking water. Our sensor platform, which we have termed a 'MAIS' (mass amplifier ion sensor), with a simple detection procedure, high sensitivity, selectivity and real practical applicability has shown potential as an early toxicity assessment of silver ions in the environment.

Highly sensitive detection of silver ions using a silver-specific DNA based nano-porous micro-resonator

Detection of silver ions is based on a frequency shift of a resonator upon interaction between silver ions and cytosine bases.

A luminescent silver–phosphine tetragonal cage based on tetraphenylethylene

A phosphine-based tetragonal cage emits strong fluorescence both in dilute solutions and in aggregated states, showing response towards anions/olefin compounds.

Ultra-sensitive in situ detection of silver ions using a quartz crystal microbalance

Label-free, ultra-sensitive and in situ detection of silver ion was achieved using a quartz crystal microbalance in laboratory conditions and drinking water.

Potentiometric aptasensing based on target-induced conformational switch of a DNA probe using a polymeric membrane silver ion-selective electrode

In this article, we introduce a general, sensitive, facile, and label-free potentiometric assay based on metal-mediated DNA base pairs. A nucleic acid with one adenosine-5'-triphosphate (ATP) binding sequence (aptamer) in the middle and two cytosine(C)-rich sequences at the lateral portions was employed as a model. A rigid hairpin structure can be formed in the presence of Ag(+) ions, in which the C residues of the spatially separated nucleotides are linked by the ions. The strong interaction between Ag(+) ions and cytosines forms a stable C-Ag(+)-C structure, which could reduce the concentration of silver ions released from the polymeric membrane silver ion-selective electrode (ISE) at the sample-membrane interface and decrease the potential response. In the presence of its target, the aptamer (the loop sequence of the probe) binds specifically to the target via reaction incubation. Such target-binding induced aptamer conformational change prevents the formation of C-Ag(+)-C structure, leaving more silver ions at the sample-membrane interface, which can be detected by the silver ISE. ATP can be quantified in the range of 0.5-3.0 μM with a detection limit of 0.37 μM. The relative standard deviation for 5 μM ATP is 5.5%. For the proposed method, the combination of using ion fluxes of silver ions as modulating reagents and as signal reporters greatly simplifies the detection procedures. In addition, by changing the binding sequence in the middle of the probe, the present detection method will be able to explore new applications of ISE for the detection of a large variety of targets.