Fluorescent detection of silver(I) and cysteine using SYBR Green I and a silver(I)-specific oligonucleotide

Abstract

We report on a novel method for the determination of silver ion (Ag + ) and cysteine (Cys) by using the probe SYBR Green I (SGI) and an Ag+-specific cytosinerich oligonucleotide (C-DNA). The fluorescence of SGI is very weak in the absence or presence of randomly coiled C-DNA. If, however, C-DNA interacts with Ag + through the formation of cytosine-Ag + -cytosine (C-Ag + -C) base pairs, the randomly coiled C-DNA undergoes a structural changes to form a hairpin-like structure, thereby increasing the fluorescence of SGI. This fluorescence turn-on process allows the detection of Ag + in the 10-600 nM concentration range, with a detection limit of 4.3 nM. Upon the reaction of Ag + with Cys, Cys specifically removes Ag + from the C-Ag + -C base pairs and destroys the hairpin-like structure. This, in turn, results in a decrease in fluorescence intensity. This fluorescence turn-off process enables the determination of Cys in the 8-550 nM concentration range, with a detection limit of 4.5 nM. The method reported here for the determination of either Ag + or Cys is simple, sensitive, and affordable, and may be applied to other detection systems if appropriately selected DNA sequences are available.

Label-free detection of kanamycin based on a G-quadruplex DNA aptamer-based fluorescent intercalator displacement assay

“…Dye/DNA probe mole ratio, pH value, and reaction time are very critical factors for label-free aptamer-based bioassays based on the staining of the dye 3 29 30 . Fig.…”

“…For fluorescent labeling, the nucleic acid dyes play an increasingly important role in the design of DNA aptamer-based bioassays because of the remarkable advantages such as being label-free and cost-effective, and having high sensitivity and selectivity, for example, the well-known organic dye SYBR Green I 29 30 31 and the metal complexes of platinum(II) metallointercalators 3 . These dyes have been reported as fluorescence probes for selectively recognizing the conformational change of DNA; unfortunately, their selectivity largely relies on the formation of double-stranded DNA, such as the T-T mismatch induced by mercury ions 29 , the C-C mismatch induced by silver ions 30 , and the hairpin-like structure induced by kanamycin as proposed by Leung et al 3 In 2006, a G-quadruplex Fluorescent Intercalator Displacement (G4-FID) assay was first developed by Teulade-Fichou and coauthors 32 for determining the quadruplex-DNA binding affinity and sequence selectivity of small-molecule ligands. The assay is based on the loss of fluorescence upon displacement of thiazole orange (TO) from quadruplex- and duplex-DNA matrices.…”

A novel biosensor based on single-layer MoS2 nanosheets for detection of Ag+

“…Moreover, they are inappropriate to be used as portable devices for real-time and on-site detection. In contrast, biosensors, especially fluorescent sensing, have great potential in high throughput detection of Ag þ on-site [4][5][6][7]. Further, rapid development of nanotechnology has provided new opportunities for improved performance of fluorescence sensors in terms of sensitivity, selectivity and reproducibility.…”

Two‐channel near‐infrared fluorescence Ag+ ion sensing of a new star‐shaped dendrimer

“…Because of the high toxicity of Ag + in organisms, monitoring Ag + levels is an important issue. It is known that silver can inactivate sulfhydryl enzymes and accumulate in the body . Many Ag + ion detection technologies, such as inductively coupled plasma mass spectrometry, atomic absorption spectra, atomic emission spectra, on‐selective electrodes and others are in use.…”