A Highly Selective and Sensitive Peptide-Based Fluorescent Ratio Sensor for Ag. J Fluoresc 2020;31:237-246. [PMID: 33215317 DOI: 10.1007/s10895-020-02653-5]

A Dipeptide-derived Dansyl Fluorescent Probe for the Detection of Cu2+ in Aqueous Solutions

A novel dansyl-based fluorescent probe (DG) was designed via the introduction of a dipeptide, glycyl-L-glutamine. DG showed good selectivity and sensitivity towards Cu2+ in aqueous solutions in the pH span of ~ 6-12. The coordination of Cu2+ with the dipeptide moiety led to the fluorescent quenching of the dansyl fluorophore. The association constant value for Cu2+ was 0.78 × 104 M- 1 in a 1 to 1 stoichiometric ratio. The detection limit in HEPES buffer solution (10 mM, pH 7.4) was 1.52 µM. DG also showed strong anti-interference capability in the presence of other metal ions. It was worth noting that DG maintained the detection ability towards Cu2+ in real water samples and cell imaging, implying the potential application opportunities in complicated environments.

Dual-emissive ratiometric fluorescent nanosensor based on multi-nanomaterials for Ag+ determination in lake water

In this study, a sensitive ratiometric fluorescent nanosensor was constructed using a facile one-pot method by encapsulating carbon dots (CDs) and cadmium telluride quantum dots (CdTe QDs) into the pore cavities of a metal-organic framework (ZIF-8). In this nanosensor (CD/CdTe QD@ZIF-8), the fluorescence attributed to CdTe QDs was quenched by silver ions (Ag⁺), and the fluorescence intensity of CDs did not change. The introduction of ZIF-8 into the system can not only adsorb Ag⁺ but also easily separate CDs and CdTe QDs from the matrix. The developed CD/CdTe QD@ZIF-8 composite used as a ratiometric fluorescent probe exhibited high sensitivity and selectivity towards Ag⁺. The working linear range was 0.1-20 μM with a limit of detection (LOD) of 1.49 nM. Finally, the proposed nanosensor was applied to determine Ag⁺ in lake water with satisfactory results.

A novel symmetrical imidazole-containing framework as a fluorescence sensor for selectively detecting silver ions

In this study, a novel and highly efficient "turn-off" fluorescence imidazole-based sensor (BIB) with a symmetric structure was synthesized by a four-step reaction, from o-phenylenediamine, 6-bromo-2-pyridinecarboxaldehyde, and 1-bromohexane. The sensing mechanism was confirmed via fluorescence titration, HRMS, and ¹HNMR techiniques. The results showed that the binding ratio of BIB and Ag⁺ was 1 : 1 in a DMF-HEPES (pH 7.4) solution (9 : 1, v/v). The fluorescence response of BIB exhibited a good linear response within the Ag⁺ concentration ranging from 2 × 10^-7 to 8 × 10^-6 mol L^-1, and the limit of detection was calculated to be 4.591 × 10^-8 mol L^-1. BIB was successfully applied to the detection of Ag⁺ in water samples with recoveries of 97.25-109.50% and relative standard deviations (RSD) of 1.14-2.45%. In addition, BIB can successfully be applied to qualitatively and quantitatively identify Ag⁺ in water by test paper strips of BIB, which is fast and convenient. This provides a possible potential for the rapid monitoring of metal ions by sensors in environmental research.

Development of a Simple Dansyl-Based PH Fluorescent Probe in Acidic Medium and Its Application in Cell Imaging

A simple pH fluorescent probe based on dansyl derivative (Bu-Dns) was synthesized via one-step reaction between dansyl chloride and 4-bromobutan-1-amine hydrobromide. The obtained probe showed good selectivity and sensitivity toward H⁺ in acidic medium over two pH units (~4-2). At pH > 4, Bu-Dns solution emitted yellow fluorescent light, which became gradually weaker with decreasing pH value. At pH below 2, complete fluorescence quenching occurred. The pH response of Bu-Dns was ascribed to the protonation of dimethylamine group. The lack of influence of metal ion on pH response increases the prevalence of Bu-Dns in the potential detection of pH variation in acidic aqueous media. More importantly, it can sense the intracellular pH change in acidic range.

Graphene Bioelectronic Nose for the Detection of Odorants with Human Olfactory Receptor 2AG1

A real-time sensor for the detection of amyl butyrate (AB) utilising human olfactory receptor 2AG1 (OR2AG1), a G-protein coupled receptor (GPCR) consisting of seven transmembrane domains, immobilized onto a graphene resistor is demonstrated. Using CVD graphene as the sensor platform, allows greater potential for more sensitive detection than similar sensors based on carbon nanotubes, gold or graphene oxide platforms. A specific graphene resistor sensor was fabricated and modified via non-covalent π–π stacking of 1,5 diaminonaphthalene (DAN) onto the graphene channel, and subsequent anchoring of the OR2AG1 receptor to the DAN molecule using glutaraldehyde coupling. Binding between the target odorant, amyl butyrate, and the OR2AG1 receptor protein generated a change in resistance of the graphene resistor sensor. The functionalized graphene resistor sensors exhibited a linear sensor response between 0.1–500 pM and high selectively towards amyl butyrate, with a sensitivity as low as 500 fM, whilst control measurements using non-specific esters, produced a negligible sensor response. The approach described here provides an alternative sensing platform that can be used in bioelectronic nose applications.