A selective, sensitive, colorimetric, and fluorescence probe for relay recognition of fluoride and Cu(II) ions with "off-on-off" switching in ethanol-water solution

A facile synthesis of a novel 4-hydroxyl-3-azo coumarin based colorimetric probes for detecting Hg2+ and a fluorescence turn-off response of 3CBD to Fe3+ in aqueous environment

Two azo dyes, (E)-3-(benzo[d]thiazol-2-yldiazenyl)-4-hydroxy-2H-chromen-2-one (3CBD) and (E)-4-hydroxy-3-(quinolin-2-yldiazenyl)-2H-chromen-2-one (3CQD), were designed and synthesized using facile methods. The structures were validated through FTIR and NMR spectroscopy. The photophysical property analyses were further studied using UV-Vis and fluorescence spectrophotometers. Consequently, the absorption and emission spectra of 3CBD confirmed its selectivity of Hg2+ and turn-off response to Fe3+. On the other hand, the absorption spectra analysis of 3CQD demonstrated selectivity in the presence of Hg2+. The colorimetric investigations demonstrated a significant visual response specifically for Hg2+, enabling real-time analysis in the corresponding solutions. The presence of other coexisting metal ions does not interfere with the detection of the target metal ion. The fluorescence studies of the two probes revealed that 3CBD was highly fluorescent, which was significantly quenched by Fe3+, upon excitation at 340 nm. Utilizing Job plot analyses, it was determined that the complexes 3CBD-Hg2+ and 3CQD-Hg2+ exhibit a binding stoichiometry of 1 : 1. The association constants for these complexes were measured to be 7.48 × 105 and 9.12 × 105 M-1, respectively, indicating a strong association between both probes and their respective metal ions. Both chemosensors exhibited comparable limits of detection (LOD) and limits of quantification (LOQ) of 0.03 μM and 0.10 μM, respectively. Reversible studies confirmed that only chemosensor 3CQD could serve as a secondary sensor for EDTA. The theoretical studies calculated using Density Functional Theory (DFT) program at B3LYP/6-31G** (Spartan '10 package) level.

Sequential detection of inflammation-related hypochlorite ions and viscosity with a relay fluorescent probe

Based on the correlation between inflammation and reactive oxygen species and viscosity, a fluorescent probe (SWJT-19) was designed for a relay detection of hypochlorite ions and viscosity. The synthesized probe could quickly and selectively detect hypochlorite ions, as well as viscosity of the system effectively. Moreover, the probe had been successfully applied to sequentially detect hypochlorite ions and viscosity in organisms, as well as imaging in mouse inflammation.

Carbohydrate-Binding Modules of Potential Resources: Occurrence in Nature, Function, and Application in Fiber Recognition and Treatment

Great interests have recently been aroused in the independent associative domain of glycoside hydrolases that utilize insoluble polysaccharides-carbohydrate-binding module (CBM), which responds to binding while the catalytic domain reacts with the substrate. In this mini-review, we first provide a brief introduction on CBM and its subtypes including the classifications, potential sources, structures, and functions. Afterward, the applications of CBMs in substrate recognition based on different types of CBMs have been reviewed. Additionally, the progress of CBMs in paper industry as a new type of environmentally friendly auxiliary agent for fiber treatment is summarized. At last, other applications of CBMs and the future outlook have prospected. Due to the specificity in substrate recognition and diversity in structures, CBM can be a prosperous and promising ‘tool’ for wood and fiber processing in the future.

Development of a fluoride-anion sensor based on aggregation of a dye-modified polyhedral oligomeric silsesquioxane

We report a new concept for a turn-on fluoride sensor based on the aggregation and release of a dye-modified polyhedral oligomeric silsesquioxane.

Small-molecule fluorescent probes based on covalent assembly strategy for chemoselective bioimaging

In this review, we comprehensively summarize the recent progress in the development of small molecular fluorescent probes based on the covalent assembly principle. The challenges and perspective in this field are also presented.

A New Reversible Colorimetric Chemosensor Based on Julolidine Moiety for Detecting F. J Fluoresc 2021;31:1675-1682. [PMID: 34387807 DOI: 10.1007/s10895-021-02801-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

We synthesized an original reversible colorimetric chemosensor PDJ ((E)-9-((2-(6-chloropyridazin-3-yl)hydrazono)methyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol) for the detection of F^-. PDJ displayed a selective colorimetric detection to F^- with a variation of color from colorless to yellow. Limit of detection of PDJ for F^- was calculated as 12.1 µM. The binding mode of PDJ and F^- turned out to be a 1:1 ratio using Job plot. Sensing process of F^- by PDJ was demonstrated by ¹H NMR titration and DFT calculation studies that suggested hydrogen bond interactions followed by deprotonation. Moreover, the practicality of PDJ was demonstrated via a reversible test with TFA (trifluoroacetic acid).

Two-Dimensional Material-Based Colorimetric Biosensors: A Review

Two-dimensional (2D) materials such as graphene, graphene oxide, transition metal oxide, MXene and others have shown high potential for the design and fabrication of various sensors and biosensors due to their 2D layered structure and unique properties. Compared to traditional fluorescent, electrochemical, and electrical biosensors, colorimetric biosensors exhibit several advantages including naked-eye determination, low cost, quick response, and easy fabrication. In this review, we present recent advances in the design, fabrication, and applications of 2D material-based high-performance colorimetric biosensors. Potential colorimetric sensing mechanisms and optimal material selection as well as sensor fabrication are introduced in brief. In addition, colorimetric biosensors based on different 2D materials such as graphene, transition metal dichalcogenide/oxide, MXenes, metal-organic frameworks, and metal nanoplates for the sensitive detection of DNA, proteins, viruses, small molecules, metallic ions, and others are presented and discussed in detail. This work will be helpful for readers to understand the knowledge of 2D material modification, nanozymes, and the synthesis of hybrid materials; meanwhile, it could be valuable to promote the design, fabrication, and applications of 2D material-based sensors and biosensors in quick bioanalysis and disease diagnostics.

The C2-Symmetry Colorimetric Dye Based on a Thiosemicarbazone Derivative and its Cadmium Complex for Detecting Heavy Metal Cations (Ni2+, Co2+, Cd2+, and Cu2+) Collectively, in DMF

The field of chemosensing has been experiencing an exponential expansion in recent times, due to increased demands for simpler and user-friendly analytical techniques, in order to combat and confront the challenges of industrial pollutions in the twenty-first century. Metal complex-based chemosensors have received little attention while exhibiting excellent sensing properties, comparing to their organic counterparts. Thus, a thiosemicarbazone-based (H) and its cadmium complex (P) were synthesized, characterized and their photophysical and chemosensing properties were investigated in DMF solvent. The addition of molar equivalents of selected cations (of nitrates or chloride salts) to H and P, produced visually detectable colour changes as well as remarkable spectral shifts. Explicitly, the two probes (H and P) were able to collectively discriminate heavy metal cations such as Cd2+, Co2+, Zn2+, Cu2+, Ni2+, and Ag+, both in DMF, among all other heavy metal cations tested. None of the anions could be detected by H or P, even when the tetrabutylammonium salts (TBAs) were used, the action presumably ascribed to the solvent effect. Thus, H and P can be used to selectively and sensitively detect the presence of heavy metal cations, via naked-eye detectable colour changes in an aqueous soluble solvent such as DMF.

Supersensitive Detection of Anions in Pure Organic and Aqueous Media by Amino Acid Conjugated Ellman's Reagent

The last few decades witnessed a remarkable advancement in the field of molecular anion receptors. A variety of anion binding motifs have been discovered, and large number of designer molecular anion receptors with high selectivity are being reported. However, anion detection in an aqueous medium is still a formidable challenge as evident from only a miniscule of synthetic systems available in the literature. We, herein, report 5,5'-dithio-bis(2-nitrobenzoic acid) (Ellman's reagent) appended with amino acids as supersensitive anion sensors that can detect F^- and H₂PO₄^- ions in both aqueous as well as organic media. Interestingly, the sensors showed a dual response to anions, viz., chromogenic response in organic medium and electrochemical response in aqueous solutions. Various spectroscopic techniques such as UV-vis and ¹H NMR are used to investigate the binding studies in acetonitrile, whereas electrochemical methods such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV) are employed to explore the anion binding in water. The host-guest complex stoichiometry and binding constants are calculated using the BindFit software. The geometry of host-guest complex has been optimized by the density functional theory (DFT) method. These molecules are versatile sensors since these function in both water and acetonitrile with extremely low limit of detection (LOD) up to 0.07 fM and limit of quantification (LOQ) up to 0.23 fM. To our knowledge, the present system is the first example of a sensor that can detect the lowest concentration of anions in water quantitatively. The minimalistic design strategy presented here opens up the innumerable possibilities for designing dual anion sensors in a one fell swoop.

Covalent-Assembly Based Fluorescent Probes for Detection of hNQO1 and Imaging in Living Cells

Human NAD(P)H: quinone oxidoreductase (hNQO1) is an important biomarker for human malignant tumors. Detection of NQO1 accurately is of great significance to improve the early diagnosis of cancer and prognosis of cancer patients. In this study, based on the covalent assembly strategy, hNQO1-activated fluorescent probes 1 and 2 are constructed by introducing coumarin precursor 2-cyano-3-(4-(diethylamino)-2-hydroxyphenyl) acrylic acid and self-immolative linkers. Under reaction with hNQO1 and NADH, turn-on fluorescence appears due to in-situ formation of the organic fluorescent compound 7-diethylamino-3-cyanocoumarin, and fluorescent intensity changes significantly. Probe 1 and 2 for detection of hNQO1 are not interfered by other substances and have low toxicity in cells. In addition to quantitative detection of hNQO1 in vitro, they have also been successfully applied to fluorescent imaging in living cells.

Rationally designed phenanthrene derivatized triazole as a dual chemosensor for fluoride and copper recognition

A 1,2,3-triazole chemosensor containing phenanthrene and phenol moieties (PhTP) was efficiently synthesized via copper (I)-catalyzed azide-alkyne cycloaddition, "click chemistry". PhTP is a dual analyte sensor for fluoride and copper (II) ions in homogeneous medium. Deprotonation of the phenolic OH proton by the fluoride ion is responsible for a change in fluorescence color from blue (PhTP) to yellowish-orange (PhTP-fluoride adduct), while a charge transfer between the triazole nitrogen of the chemosensor and Cu²⁺ revealed a turn-off fluorescence output. The detection capability of PhTP was analyzed with a series of anions (F^-, Cl^-, Br^-, I^-, H₂PO₄^-, ClO₄^-, OAc^-, BF₄^-) and cations (Fe³⁺, Fe²⁺, Cu²⁺, Ag⁺, Cr³⁺, Al³⁺, Co²⁺, Ni²⁺, Cd²⁺, Zn²⁺). With anions, competitive fluorescence responses under UV lamp were observed for acetate and dihydrogen phosphate anions, but maximum response from fluoride ion was substantiated from steady state absorption and fluorescence experiments. With cations, PhTP displayed a selective and sensitive recognition towards Cu²⁺ ion through spectral modulation in absorption spectroscopy and a turn-off fluorescence response. Nuclear magnetic resonance (NMR) spectroscopic titration studies supported the results obtained through photophysical studies and provided evidence for the ion-binding sites on the probe.

A colorimetric probe for the real-time naked eye detection of cyanide and hydroxide ions in tap water: experimental and theoretical studies

Herein, a colorimetric sensor (L) based on a naphthyl derivative bearing hydrazone receptors was synthesized via a one-step reaction process, and its recognition properties towards biologically important anions in an acetonitrile-water mixture were investigated by naked-eye observation and UV-Vis and ¹H NMR spectroscopy. The molar addition of anions, such as TBAF^-, TBAOH^-, TBACN^- and TBAAcO^-, induced a significant red shift in the charge transfer band (Δλ = 73 nm, from 337 nm to 410 nm), in agreement with visible "naked eye" detectable colorimetric activities; in addition, soaked-in-L paper strips were prepared, which could significantly discriminate cyanide (KCN) and hydroxide (NaOH) ions dissolved in tap water via the litmus test method. This study was complemented by density functional theory computations to gain more insight into the interaction between L and anions.

Deeper insight into protease-sensitive "covalent-assembly" fluorescent probes for practical biosensing applications

We report a rational and systematic study devoted to the structural optimisation of a novel class of protease-sensitive fluorescent probes that we recently reported (S. Debieu and A. Romieu, Org. Biomol. Chem., 2017, 15, 2575-2584), based on the "covalent-assembly" strategy and using the targeted enzyme penicillin G acylase as a model protease to build a fluorescent pyronin dye by triggering a biocompatible domino cyclisation-aromatisation reaction. The aim is to identify ad hoc probe candidate(s) that might combine fast/reliable fluorogenic "turn-on" response, full stability in complex biological media and ability to release a second molecule of interest (drug or second fluorescent reporter), for applications in disease diagnosis and therapy. We base our strategy on screening a set of active methylene compounds (C-nucleophiles) to convert the parent probe to various pyronin caged precursors bearing Michael acceptor moieties of differing reactivities. In vitro stability and fluorescent enzymatic assays combined with HPLC-fluorescence analyses provide data useful for defining the most appropriate structural features for these fluorogenic scaffolds depending on the specifications inherent to biological application (from biosensing to theranostics) for which they will be used.

A coumarin-based fluorescent probe for specific and rapid detection of fluoride ions

A simple and coumarin-based fluorescence probe has been designed and synthesized with silyl group as recognition group of fluoride ions (F−) in this study. The results showed that the fluorescence intensity of the probe displayed prominent enhancement with addition of F− at 445 nm with incubation of 1 min. There was an excellent linear relationship between fluorescence intensity and fluoride concentration from 0 to 30 μM (0~0.57 ppm), which offered the important condition for the quantitative analysis. In addition, the highly selective response to fluorion, the low detection limit with 28 nM (0.532 ppb), low toxicity and bioimaging afforded an advantage for practical application and detecting fluoride in biological systerms.

A macrocyclic tetranuclear ZnII complex as a receptor for selective dual fluorescence sensing of F− and AcO−: effect of a macrocyclic ligand

Fluorimetric detection of F⁻/AcO⁻ with an additional ‘INHIBIT’ logic gate response for F⁻/H⁺ and AcO⁻/H⁺ in an aqueous-methanol medium by a 48-membered macrocyclic Zn^II-complex DAS has been explored by combined experimental and theoretical study.

A new multifunctional benzimidazole tagged coumarin as ratiometric fluorophore for the detection of Cd2+/F- ions and imaging in live cells

A novel multifunctional ratiometric fluorescent probe has been designed and synthesized for the selective recognition of Cd²⁺/F^- ions. The probe (3)-((2)-(1H-benzoimidazole-2-yl)-phenylimino) methyl-4-chloro-methyl-2H-chromen-2-ene (BIMC) displays excellent ratiometric responses towards Cd²⁺/F^- ions over the tested cations/anions. The lowest detection limits observed for Cd²⁺ and F^- are 1.5 × 10^-10 mol/l and 1.2 × 10^-10 mol/l respectively. Job's plot and Electro spray Ionization mass spectral (ESI-MS) studies confirms 1:1 binding stoichiometry of BIMC with Cd²⁺/F^- ions, which is further evidenced by ¹H NMR titration studies. The reversibility studies of BIMC with Cd²⁺ have been investigated using ethylenediaminetetraacetic acid (EDTA). Upon binding to Cd²⁺/F^- ions, the probe features strong ratiometric response in both UV-Visible and fluorescence spectra due to the inhibition of intramolecular charge transfer (ICT). Furthermore, the mechanism of ICT has been rationalized via solvatochromism and DFT calculations.

A novel rhodamine B-based "off-on'' fluorescent sensor for selective recognition of copper (II) ions

A novel rhodamine based sensor RBH was developed and synthesized by rhodamine B with 3-methyl-2-benzothiazolinone hydrazone, which exhibited high selectivity and sensitivity for sensing Cu²⁺ ions in the presence of other important relevant metal ions in aqueous acetonitrile. As an "off-on" fluorescent sensor, RBH exhibited a UV-vis absorption increase at 570 nm and a 132-fold significant fluorescence enhancement at 580 nm with a distinct color change from colorless to purple upon the addition of Cu²⁺ ions. The fluorescence intensity of RBH is linear with the Cu²⁺ ions concentration with low limit of detection. Furthermore, the sensor RBH has been successfully utilized for fluorescence imaging of Cu²⁺ ions in living cells. The sensor could potentially recognize Cu²⁺ ions in biological system.

Sensitive fluorescence on-off probes for the fast detection of a chemical warfare agent mimic

Two highly sensitive probes bearing a nucleophilic imine moiety have been utilized for the selective detection of chemical warfare agent (CWA) mimics. Diethyl chlorophosphate (DCP) was used as mimic CWAs. Both iminocoumarin-benzothiazole-based probes not only demonstrated a remarkable fluorescence ON-OFF response and good recognition, but also exhibited fast response times (10s) along with color changes upon addition of DCP. Limits of detection for the two sensors 1 and 2 were calculated as 0.065μM and 0.21μM, respectively, which are much lower than most other reported probes. These two probes not only show high sensitivity and selectivity in solution, but can also be applied for the recognition of DCP in the gas state, with significant color changes easily observed by the naked eye.

A Cu(ii) mediated approach for colorimetric detection of aqueous fluoride in ppm level with a Schiff base receptor

Inspired by the importance of fluoride detection in aqueous environment, a new methodology is demonstrated by employing the synergistic reaction of fluoride and Cu(ii) salts with a designed Schiff base receptor.

A new azine derivative colorimetric and fluorescent dual-channel probe for cyanide detection

A novel azine derivative colorimetric and fluorescent dual-channel probe salicylaldehyde hydrazine-3,5-dibromosalicylaldehyde (1) has been designed, synthesized and characterized. The probe 1 is confirmed to have especial selectivity and good sensitivity on detecting CN^- via UV-vis absorption and fluorescence spectrum in aqueous solution (H₂O/DMSO, 1:4, v/v). This colorimetric and fluorescent dual-channel probe response to CN^- owed to the deprotonation process and established the mechanism by using ¹H NMR spectroscopy. Further researches showed that the detection limit of the probe 1 to CN^- anions is 8.01×10^-9M, significantly lower than the maximum level 1.9×10^-6M in potable water from WHO guidelines.

Fluorescein-Based Chromogenic and Ratiometric Fluorescence Probe for Highly Selective Detection of Cysteine and Its Application in Bioimaging

A dual mode fluorescent probe, which is based on an integration of fluorescein and coumarin fluorophores, was developed for the discrimination of Cys from Hcy and GSH. This probe (2) shows the advantage of quick reaction (5 min) with Cys, resulting in a strong fluorescence turn-on response when excited at 450 nm. Notably, it also demonstrates the ratiometric fluorescence property while excited by a shorter wavelength (332 nm). All of results suggest probe 2 has a high selectivity toward Cys even in the presence of other amino acids, cations and anions. The detection limit of Cys was calculated as 0.084 μM, which was much lower than the intracellular concentration. ¹H NMR, MS and DFT calculation were used to reveal the detection mechanism further. Finally, this low cytotoxic probe was successfully applied in bioimaging within HepG2 cells.

How explosive TNP interacts with a small tritopic receptor: a combined crystallographic and thermodynamic approach

The interaction of explosive and pollutant TNP with the host receptor has been thoroughly explained and characterized by SCXRD and thermodynamic parameters.

A fluorescein-based chemosensor for relay fluorescence recognition of Cu(ii) ions and biothiols in water and its applications to a molecular logic gate and living cell imaging

Relay recognition of copper(ii) ions and biothiolsviaa fluorescence “on–off–on” cascade has been realized in 100% aqueous solution when excited by the visible light.

Single fluorescent chemosensor for multiple targets: sequential detection of Al3+ and pyrophosphate and selective detection of F− in near-perfect aqueous solution

An easily fabricated chemosensor was developed for selective fluorescence detection of three analytes, Al³⁺, pyrophosphate (PPi), and F⁻, in aqueous solution.

Lysosome-Targeted Turn-On Fluorescent Probe for Endogenous Formaldehyde in Living Cells

As one of the simplest reactive carbonyl species, formaldehyde is implicated in nervous system diseases and cancer. Organelles play crucial roles in various physiological processes in living cells. Accordingly, the detection of endogenous formaldehyde at the subcellular level is of high interest. We herein describe the development of the first organelle-targeted fluorescent formaldehyde probe (Na-FA-Lyso). The new probe exhibits favorable features including a large fluorescence enhancement (about 350-fold) and a fast response to formaldehyde. Significantly, the novel probe Na-FA-Lyso was employed to visualize the endogenous formaldehyde in the lysosomes in living cells for the first time.

A colorimetric sensor for the selective detection of fluoride ions

A colorimetric receptor L was prepared. Receptor L can selectively sense F^- based on distinct color changes among a series of ions. It can selectively sense F^- through an intramolecular hydrogen bond interaction. A Job plot indicated a 1:1 complexation stoichiometry between receptor L and F^- . The association constant for L-F^- in CH₃ CN was determined as 9.70 × 10⁴  M^-1 using a Stern-Volmer plot.