A label-free fluorescent probe for Hg2+ and biothiols based on graphene oxide and Ru-complex

Abstract

A novel, selective and sensitive switch-on fluorescent sensor for Hg2+ and switch-off fluorescent probe for biothiols was developed by using [Ru(bpy)2(pip)]2+ as the signal reporter and graphene oxide (GO) as the quencher. Due to the affinity of GO towards single-stranded DNA (ss-DNA) and [Ru(bpy)2(pip)]2+, the three components assembled, resulting in fluorescence quenching. Upon addition of Hg2+, a double-stranded DNA (ds-DNA) via T–Hg2+–T base pairs was formed, and [Ru(bpy)2(pip)]2+ intercalated into the newly formed ds-DNA. Then, [Ru(bpy)2(pip)]2+ and ds-DNA were removed from the surface of GO, resulting in the restoration of fluorescence. Subsequently, upon addition of biothiols, Hg2+ was released from ds-DNA, due to the higher affinity of Hg2+ to the sulfur atoms of biothiols, which could induce ds-DNA unwinding to form ss-DNA. Then ss-DNA and [Ru(bpy)2(pip)]2+ were adsorbed on the surface of GO, the fluorescence of [Ru(bpy)2(pip)]2+ was quenched again. Therefore, the changes in emission intensity of [Ru(bpy)2(pip)]2+ directly correlated to the amount of detection target (Hg2+ or biothiols) in solution. The assay exhibited high sensitivity and selectivity, with the limits of detection for Hg2+, cysteine (Cys) and glutathione (GSH) to be 2.34 nM, 6.20 nM and 4.60 nM, respectively.

Luminescent turn-on detection of Hg(II) via the quenching of an iridium(III) complex by Hg(II)-mediated silver nanoparticles

“…Notably, a limit of detection (LOD) for Hg(II) was calculated to be 5 nM according to the equation C lim  = 3δ/ k , which is lower than the maximum permissible level (10 nM) of Hg(II) in drinking water specified by the U.S. Environmental Protection Agency (EPA) 7, 46 . Additionally, the sensitivity of this proposed method is also found to be comparable to other reported methods for Hg(II) detection as summarized in Table S2 (ESI†) 6–8, 12, 13, 17,19–22, 47–53 .

Figure 5( a ) Luminescence emission spectra of 1.0 μM complex 1 in Tris-HNO 3 buffer solution (pH 7.0) containing 0.4 μM Ag nanoparticles and different concentrations of Hg(II) (from bottom to top: 0, 20, 40, 60, 80, 100, 120, 140, 160, 180, 220, 270, 360, and 520 nM). ( b ) Luminescence intensities of the 1 /AgNP system (1.0 μM 1 and 0.4 μM AgNPs in Tris-HNO 3 at pH 7.0) in the presence of Hg(II) (180 nM) or interfering species (1 μM).

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"Turn on" and label-free core−shell Ag@SiO2 nanoparticles-based metal-enhanced fluorescent (MEF) aptasensor for Hg2+

“…This is an exceptionally low or comparable result compared with other turn-on fluorescent methods for Hg 2+ . For example, the quantum dots and gold nanoparticles fluorescent sensor (0.18 nM) 29 , the [Ru (bpy) 2 (pip)] 2+ and graphene oxide (GO) system (2.34 nM) 28 , the evanescent wave fiber optic biosensors (1.2 nM) 27 . To the best of our knowledge, this is the first complex of the Ag@SiO 2 NPs MEF ability and the Hg 2+ aptasensor.…”

“…Most of the existing fluorescent Hg 2+ aptasensor required fluorophores or quencher labeling to the oligonucleotide probes 26 27 , which was cost- and time-consuming and increases the complexity. Recently, Cao and Sun group has reported a label-free fluorescent probe 28 for Hg 2+ by directly added the signal fluorophores and quencher molecules into the solution based on the fluorescence resonance energy transfer (FRET) signals. However, the fluorescence signals will be affected by the fluorophores or quencher molecule interaction to the T−Hg 2+ −T complex so that the repeatability of this sensor was poor without rigorous experiment conditions control.…”

Triple Raman Label‐Encoded Gold Nanoparticle Trimers for Simultaneous Heavy Metal Ion Detection

“…[ 3 ] Therefore, much effort has been devoted to the sensitive and selective detection of Hg 2+ and Ag + based on different signal transduction mechanisms. [4][5][6][7][8][9][10] Traditional methods, such as cold-vapor atomic absorption spectrometry, chromatography, and inductively coupled plasma mass spectroscopy (ICP-MS), have been extensively used. However, most of these techniques are expensive, labor-intensive, and time-consuming.…”