title: 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 Hg(2+) 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 Hg(2+), a double-stranded DNA (ds-DNA) via T-Hg(2+)-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, Hg(2+) was released from ds-DNA, due to the higher affinity of Hg(2+) 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 (Hg(2+) or biothiols) in solution. The assay exhibited high sensitivity and selectivity, with the limits of detection for Hg(2+), cysteine (Cys) and glutathione (GSH) to be 2.34 nM, 6.20 nM and 4.60 nM, respectively.
authors.affiliation: Department of Chemistry, Tongji University, Shanghai 200092, China.
authors.forename: Linlin
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Chemistry, Tongji University, Shanghai 200092, China.
authors.forename: Tianming
authors.initials: T
authors.lastname: Yao
authors.affiliation: Department of Chemistry, Tongji University, Shanghai 200092, China.
authors.forename: Shuo
authors.initials: S
authors.lastname: Shi
authors.affiliation: Department of Chemistry, Tongji University, Shanghai 200092, China.
authors.forename: Yanlin
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Department of Chemistry, Tongji University, Shanghai 200092, China.
authors.forename: Wenliang
authors.initials: W
authors.lastname: Sun
mesh_terms: D015374:Biosensing Techniques / Q000379:methods; D003545:Cysteine / Q000032:analysis / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D004277:DNA, Single-Stranded / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry*; D005978:Glutathione / Q000032:analysis / Q000737:chemistry; D006108:Graphite / Q000737:chemistry*; D008628:Mercury / Q000032:analysis* / Q000737:chemistry; D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D009942:Organometallic Compounds / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry; D015203:Reproducibility of Results; D012428:Ruthenium / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013438:Sulfhydryl Compounds / Q000032:analysis* / Q000737:chemistry
chemical_list: D004277:DNA, Single-Stranded; D005456:Fluorescent Dyes; D009942:Organometallic Compounds; D010087:Oxides; D013438:Sulfhydryl Compounds; D006108:Graphite; D012428:Ruthenium; D004247:DNA; D008628:Mercury; D005978:Glutathione; D003545:Cysteine