Dansyl-Modified γ-Cyclodextrin as a fluorescent sensor for molecular recognition

Dansyl-Modified -Cyclodextrin (1) has been prepared as a sensor for detecting organic compounds.1 shows pure monomer fluorescence whose intensity is decreased or enhanced upon addition of guest species. The value I/I ⁰, whereI andI ⁰ are fluorescence intensities in the presence and absence of a guest and I isI ⁰–I, was used as a parameter of sensitivity.1 exhibits highly sensitive and selective molecular recognition ability, particularly, for ursodeoxycholic acid, chenodeoxycholic acid, and lithocholic acid.     

A fluorescent molecular ruler as a selective probe for ω-aminoacids

A fluorescent probe for ω-aminoacids behaves as a molecular ruler, changing the yellow fluorescent emission into blue as a function of the distance between the terminal ammonium and the carboxylate groups, permitting the quantitative detection of ω-aminoacids, their metabolites and related drugs, such as pregabalin or gabapentin, from pharmaceutical formulations.     

Spacer effect of appended moieties for molecular recognition in doubly-sodium anthranilate modified γ-cyclodextrin

-Cyclodextrin with two sodium anthranilate moieties (1) has been prepared as a sensor for detecting organic compounds including terpenoids and steroids. Compound1 shows a pure monomer fluorescence whose intensity is increased or decreased upon addition of the guest species examined. In this system, the sodium anthranilate moieties act either as a spacer, which enables the cyclodextrin to form a 1:1 host-guest complex by narrowing the -cyclodextrin cavity, or as a hydrophobic cap.1 recognizes steroids with much higher sensitivity than terpenoids, in which the appended moieties act as a hydrophobic cap for terpenoids and a spacer for steroids, respectively.     

1,2-dithioglycol functionalised carbon nitride quantum dots as a “turn – off” fluorescent sensor for mercury ion detection

A kind of 1,2-dithioglycol (DTG) functionalised carbon nitride quantum dots (DTG-CNQDs) was designed for the first time by modifying DTG on the surface of carbon nitride quantum dots (CNQDs). The as-prepared DTG-CNQDs exhibit strong blue fluorescence under ultraviolet light and have a high quantum yield of 27%. Experiments show that Hg²⁺ has a good quenching effect on the fluorescence of DTG-CNQDs. In phosphate buffer (PBS, 10 mM, pH 6.0), the fluorescence quenching rate (F₀/F) has a good linear relationship with the concentration of Hg²⁺ in the range of 0.020–0.50 μM with detection limit of 0.63 nM. This fluorescent probe possesses high sensitivity and good selectivity, which can be applied in the rapid detection of Hg²⁺ in tap and lake water samples.     

A self-assembled tetrapeptide that acts as a “turn-on” fluorescent sensor for Hg2+ ion

The tetrapeptide (Bz-$\mathrm{\Delta }$Phe(p-NPh₂)-l-DOPA(protected)-l-Phe-l-Phe-OMe was designed to incorporate seven phenyl rings so that it’s conformation, self-assembly and application in Hg²⁺ ions sensing could be studied. Peptide molecules adopted an overlapping β-turn of type III/III conformation in crystals. The peptide showed a highly selective turn-on response towards mercuric ion over other metal ions with a 10-fold enhancement in fluorescence intensity. This intensity change coupled with the selectivity of the peptide towards mercury allowed us to demonstrate simple colorimetric dip sensing of Hg²⁺ ions. The technique provides a highly selective and effective way to detect Hg²⁺ ions. The peptide also self-assembled into nanospheres with diameter ranges from 100 to 500?nm. Mercuric ion coordination enabled these peptide nanospheres to aggregate into well-defined nanoparticles. The enhanced fluorescence upon Hg²⁺ addition demonstrates that peptide scaffolds can be exploited in the development of different selective sensors.     

A reversible fluorescent–colorimetric Schiff base sensor for Hg ion

A simple (R)-(−)-2-phenylglycinol functionalized Schiff base L1 and its characterization as a fluorescent–colorimetric sensor for Hg²⁺ ion are described. The UV–vis and fluorescence analysis in methanol and aqueous solution show complex formation between L1 and Hg²⁺ ion with a micromolar association constant. Competition experiments performed for the acetate salts of Hg²⁺, Zn²⁺, Co²⁺, Pb²⁺, Cd²⁺, Mn²⁺, Cu²⁺, Ni²⁺, and Ba²⁺ revealed that compound L1 exhibits high selectivity toward Hg²⁺ displaying a color change easily detectable by naked-eye and a turn-off fluorescent effect due to a chelation-enhanced quenching (CHEQ) mechanism. Moreover, addition of EDTA to L1–Hg²⁺ recovers the fluorescence and color offering receptor L1 as a reversible sensor for real-time applications.     

A thienoquinoxaline and a styryl-quinoxaline as new fluorescent probes for amyloid-β fibrils

Simple and easy to prepare quinoxaline derivatives proved able to stain amyloid fibers such as aggregated lysozyme and Aβ(1-40)-peptide by a fluorescence “turn on” mechanism. Thienoquinoxaline 1 allowed the detection of lysozyme and Aβ(1-40) fibers at λ = 555 and 532 nm, respectively, with excitation at λ = 450 nm. Styryl-quinoxaline 2 stained lysozyme and Aβ(1-40) fibers with fluorescence at λ = 579 and 567 nm, respectively, upon excitation at λ = 453 nm. The apparent K_d values for Aβ(1-40) fibers were 77 and 294 nM for 1 and 2, respectively. The sensitivity of the aggregates detection assay with these new dyes was higher than that of thioflavin T. Considering their unique fluorescence properties compared to other dyes reported in the field, they can be considered as additional staining tools for the detection and studies of peptide/protein aggregation.     

Carbon-dot-based dual-emission nanohybrid produces a ratiometric fluorescent sensor for in vivo imaging of cellular copper ions

A sensitive biosensor: A strategy for the intracellular imaging of Cu(2+) ions has been developed by integrating a recognition molecule, N-(2-aminoethyl)-N,N,N'tris(pyridin-2-ylmethyl)ethane-1,2-diamine (AE-TPEA), into a hybrid system composed of carbon and CdSe/ZnS quantum dots.     

1-Pyrenecarboxaldehyde thiosemicarbazone:A novel fluorescent molecular sensor towards mercury(Ⅱ) ion

<正>A novel and simple fluorescent molecular sensor,1-pyrenecarboxaldehyde thiosemicarbazone(Hpytsc),was synthesized.Its higher sensitivity and selectivity to mercury(Ⅱ) ion were studied through absorption and emission channels.The UV-vis spectra show that the increasing mercury(Ⅱ) ion concentrations result in the decreasing absorption intensity.The fluorescence monomer emission of Hpytsc is enhanced upon binding mercury(Ⅱ) ion,which should be due to the 1:1 complex formation between Hpytsc and metal ion.     

A chiral perazamacrocyclic fluorescent sensor for cascade recognition of Cu(II) and the unmodified α-amino acids in protic solutions

A novel chiral Perazamacrocyclic fluorescent sensor (1) was designed and synthesized. It can serve as a fluorescent turn-off sensor with high selectivity toward Cu(II) among 14 metal ions. Furthermore, though 1 exhibits no enantioselectivity, after adding Cu(II), the in situ generated Cu(II)-containing complex of 1 (Cu(II)-1) can exhibit remarkable fluorescent enhancement responses and considerable enantioselectivities toward unmodified α-amino acids in protic solutions via a ligand displacement mechanism; i.e. a cascade recognition of Cu(II) and unmodified α-amino acids has been achieved.     

Cyclodextrin as a Template for Molecular Assembly: Formation of Heterodimers Between a Polyamino- and a Polysulfonato-β-Cyclodextrin

A poly(hydroxyethylamino)- and a poly(sulfonatophenyloxy)--cyclodextrin derivative, bearing opposite ionic charges, have been shown by potentiometric titration to form stable pH-dependent heterodimers with each other in water. The formation constants of these dimers show that a very stable assembly is formed between the fully deprotonated sulfonato derivative and the fully protonated amino derivative (log K_a = 8.5), which constitutes the assembly of multiple extended atomic groupings on cyclodextrin as template.     

Organic-inorganic hybrid fluorescent sensor thin films of rhodamine B embedded Ag-SBA 15 for selective recognition of Hg (Ⅱ) ions in water

Nowadays, the rapid and effective detection of low doses of heavy metal pollutants in contaminated water is a timely challenge in environmental pollution research. In this study, a rapid and highly sensitive assay for the detection of Hg~(2+)based on quenching of metal-enhanced fluorescence of rhodamine B(RB)has been fabricated. RB and silver nanoparticle were incorporated into the mesoporous siliceous framework spin cast on a quartz glass through post-synthetic incorporation method. The morphology and crystallinity of mesoporous structure and Ag nanoparticle were characterized by transmission electron microscopy and X-ray diffraction analyses. Photoluminescence assays on the hybrid thin film of RB-Ag-SBA15 showed a high enhancement when compared to the intensity of silver free SBA15-RB in the wavelength of 575 nm. The fluorescence of RB-Ag-SBA15 thin film decreased gradually with the increase in the concentration of Hg~(2+)and the detection limits were 10.54 nmol/L. Furthermore, the fluorescence intensity increased linearly with the concentration of Hg~(2+)in the range from 1.0 ? 10à8mol/L to10 ? 10à8mol/L, with a response time of a few seconds. In addition, this system offers a high selectivity over interfering cations such as Cd~(2+) and Pb~(2+). Overall, we have developed an optical assay having a wellordered mesoporous SBA15 containing Ag-RBfor selective detection of Hg~(2+)in aqueous solution. The scheme combines the advantages of specific binding interactions between Hg~(2+)and RB molecule and optical emission properties of RB. The method is suitable for a single-shot and irreversible analytical assay in a quartz glass/microtiter plate.     

Protein recognition by bivalent, ‘turn-on’ fluorescent molecular probes

We show that the conversion of a known intercalating dye (i.e., thiazole orange) into a bivalent protein binder could lead to the realization of a novel class of ‘turn-on’ fluorescent molecular probes that detect proteins with high affinity, selectivity, and a high signal-to-noise (S/N) ratio. The feasibility of the approach is demonstrated with monomolecular probes that light-up in the presence of three different proteins: acetylcholinesterase (AChE), glutathione-s-transferase (GST), or avidin (Av) at low concentrations and with minimal background signal. The way by which such probes can be used to detect individual protein isoforms and be applied in inhibitor screening, cell imaging, and biomarker detection is described.     

β-Cyclodextrin as a mimetic of the natural GFP-chromophore environment

The green fluorescent protein (GFP) chromophore has been anchored to β-cyclodextrin (βCD) via a copper(I)-catalyzed azide-alkyne cycloaddition. The photophysical properties of this new GFP-CD derivative have been evaluated, showing the formation of a self-inclusion complex and enhancement of fluorescence of the GFP-chromophore covalently bound to the βCD. This enhancement of fluorescence by encapsulation and hence fixation of the chromophore in a binding pocket mimics the effect exerted by the natural protein environment.     

Tuneable fluorescent marker appended to β-cyclodextrin: a pH-driven molecular switch

The photophysical properties of a pH dependent molecular switch based on pyridin-4-yl indolizin β-cyclodextrin 1 in water are described. The reversibility phenomena of fluorescent emission is attributed to a molecular motion of enclosed fluorescent moiety to inside/outside location.     

Salen-based chiral fluorescence polymer sensor for enantioselective recognition of α-hydroxyl carboxylic acids

(R,R)-Salen-based chiral polymer P-1 was synthesized by the polymerization of 5,5'-((2,5-dibutoxy-1,4-phenylene)bis(ethyne-2,1-diyl))bis(2-hydroxy-3-(piperidin-1-ylmethyl) benzaldehyde (M-1) with (1R,2R)-cyclohexane-1,2-diamine (M-2) via nucleophilic addition- elimination reaction, and (R,R)-salan-based polymer P-2 could be obtained by the reduction reaction of P-1 with NaBH(4). (R,R)-Salen-based chiral polymer P-1 can exhibit greater fluorescence enhancement response toward (l)-α-hydroxyl carboxylic acids, and the value of enantiomeric fluorescence difference ratio (ef) can reach as high as 8.41 for mandelic acid and 6.55 for lactic acid. On the contrary, (R,R)-salan-based chiral polymer P-2 shows obvious fluorescence quenching response toward α-hydroxyl carboxylic acids. Most importantly, (R,R)-salen-based polymer P-1 can display bright blue fluorescence color change in the presence of (l)-α-hydroxyl carboxylic acids under a commercially available UV lamp, which can be clearly observed by the naked eyes.     

Dinitrophenylhydrazine: β-cyclodextrin inclusion complex as a novel fluorescent chemosensor probe for Ce4+

Research on Chemical Intermediates - An inclusion complex of 2,4-dinitrophenyl hydrazine (DNPH) with β-cyclodextrin (β-CD) was prepared and investigated using UV–visible and...     

A ratiometric fluorescent sensor for tracking Cu(Ⅰ) fluctuation in endoplasmic reticulum

A two-photon ratiometric fluorescent sensor for Cu~+ in endoplasmic reticulum(ER), CNSB, was developed via coumarin/ASBD integration based on FRET mechanism. In solution, CNSB shows reversible, highly-specific ratiometric response to Cu~+ .Moreover, CNSB exhibits suitable K_d value, suggesting the possibility of detecting Cu~+ in the living cells. The probe can enter the MCF-7 cells easily and specifically locates in the ER. The highly specific ratiometric response of CNSB toward Cu~+ in MCF-7 cells provides the sensor the capacity to visualize both exogenous and endogenous Cu~+ in the ER via fluorescence imaging.Next, CNSB was utilized to detect the fluctuation and distribution of Cu~+ under ER stress in MCF-7 cells, which confirmed directly the relationship between Cu~+ enhancement and ER stress. Meanwhile, the two-photon ability of coumarin facilitated the sensor to visualize Cu~+ fluctuation via two-photon fluorescence imaging. In addition, the spatial distribution of Cu~+ in the heart slice of the 14-day-old rat was demonstrated using CNSB. This study demonstrates the promising potential of CNSB in clarifying the Cu~+ -dependent signaling in the ER stress-related diseases.     

Etodolac:β-cyclodextrin inclusion complex as a novel fluorescent chemosensor probe for Ba2+

The inclusion complex of etodolac (ETD) with β-CD was investigated by UV-visible and fluorescence spectroscopy. The chemosensory ability of ETD:β-CD complex for various metal cations was investigated thoroughly, and we found that the emission of the complex showed a drastic increase in the intensity for Ba²⁺. Competitive experiments of ETD:β-CD complex with Ba²⁺ showed that no significant variation was found in the fluorescence intensity of the ETD:β-CD/Ba²⁺ complex upon adding other cations, such as Na⁺, Ag⁺, Hg²⁺, Cd²⁺, Al³⁺, Cr³⁺, Fe³⁺, Se⁴⁺, and Ti⁴⁺. The linearity range, limit of detection (LOD), and limit of quantitation (LOQ) were determined from the selectivity and sensitivity studies.     

In vivo tumor imaging by a γ-glutamyl transpeptidase-activatable near-infrared fluorescent probe

Analytical and Bioanalytical Chemistry - γ-Glutamyl transpeptidase (GGT), overexpressed in various cancer cells, has been perceived as a latent tumor biomarker. Thus, developing near-infrared...