Novel Fluorescent Chemosensors Based on Tryptophan Unit for Cu2＋ and Fe3＋ in Aqueous Solution

We reported four fluorescent chemosensors containing tryptophan units.The fluorescence spectrum titration experiments suggest that chemosensors 1,2,3 and 4 are highly selective for Cu2＋ and Fe3＋ over Li＋,Na＋,K＋,Co2＋,Zn2＋,Ni2＋,Hg2＋ and Cr3＋ via forming complexes with Cu2＋ or Fe3＋,which is confirmed by dramatical quench of fluoreseence in aqueous solution at pH 7.4,thus making all the chemosensors suitable for Cu2＋ and Fe3＋ fluorescent sensors.

Sensitive and Selective Fluorescent Chemosensors Combining Multiple PET Processes for Ag＋ Sensing

In this work, a novel fluorescent chemosensor combining multiple photoinduced electron transfer（PET） processes for the detection ofAg＋ ion was synthesized. The PET processes were derived from the lone electron pair of the selenium donors and the tertiary nitrogen atom of the coumarin fluorophore, which have not yet been used in the fluorescent chemosensor designed for Ag＋ ion. Interestingly, the chemosensors showed fluorescent responses to Ag＋ ion with a fluorescence enhancement factor of 3--5-fold by blocking the intramolecular PET quenching path- ways. Furthermore, the probe exhibited high selectivity and sensitivity for Ag＋ ion over other relevant species with detection limit down to 10 nmol/L level. The chemosensors also showed excellent performances in analyzing natural water samples. The chemosensors developed herein represent a new strategy for the PET fluorescent chemosensor design for the detection ofAg＋ ion.

Novel Highly Selective Fluorescent Chemosensors for Hg（Ⅱ）

Based on Rhodamine,two novel fluorescent Hg2＋ chemosensors（R1,R2） were synthesized from inexpensive starting materials.They were designed and synthesized with o-aminophenol and o-phenylenediamine derivatives as the Hg2＋ chelator,the comparison between the photophysical properties of two chemosensor molecules was made.The chemosensors were designed with a photoinduced electron transfer（PET） mechanism.After binding to Hg2＋ which blocks the PET process,the fluorescence intensity of the chemosensors was enhanced by up to 15-fold.They exhibit very strong fluorescence responses to Hg2＋ and have remarkably higher selectivity for Hg2＋ than for other metal ions including K＋,Na＋,Ca2＋,Mg2＋,Cd2＋,Mn2＋,Ni2＋,Co2＋,Zn2＋,Cu2＋,Cr3＋,Fe3＋,pb2＋,Ag＋,Al3＋,Fe2＋ and Sn2＋ in Tris-HC1/sodium phosphate buffer.The fluorescence enhancement of R2 towards Hg2＋ maintains stable in wide pH span（6.4-8.8） aqueous solutions.

Fluorescence chemosensors with pyrene and their interaction with nucleotide phosphate

A group of fluorescence chemosensor with pyrene, compounds (I), (II) and (III), were synthesized. The fluorescence spectra and the lifetime of these compounds were carefully measured. The fluorescence quenching spectra of pyrenyl butyric acid, compounds (I), (II) and (III) by different nucleotide phosphates, AMP ADP, ATP, dTTP, were also recorded and studied. The quenching and the stability constants were calculated by Stern-Volmer equation and eq. (2), respectively. The mechanism of interaction between fluorescence chemosensor and nucleotide phosphate was didscussed based on the comparison of the results obtained with the CPK model of free molecules of these com-pounds in the ground state.

Group 8–9 Metal‑Based Luminescent Chemosensors for Protein Biomarker Detection

The development of transition metal complex-based luminescent chemosensors has recently aroused increasing interest for protein biomarker labelling and detection,especially for the real-time diagnosis and treatment of disease.This is owing to their unique photophysical properties,particularly their long-lived and environmentally sensitive emission,which can be easily controlled via the structural modification of ligands.In this overview,we highlight recent examples of protein biomarker detection using group 8–9 metal-based luminescent chemosensors,including the frequently employed ruthenium(II)and iridium(III)complexes.Various mechanisms and sensing modes are described and compared,and the outlook and future directions of this field are discussed as well.

Theoretical study of thiourea derivatives as chemosensors for fluoride and acetate anions

The different interactions between a chemosensor, 1-（naphthalen-2-yl）-3-（6-nitrobenzothiazol-2-yl）-thiourea （1）, and F, acetate （AcO-）, Cl-, and Br- anions have been investigated theoretically at the B3LYP/6-31＋G（d,p） level with the basis set superposition error （BSSE） correction. It was found that the high selectivity of compound 1 for F- can be ascribed to the ability of the anion to deprotonate the N-H fragment of the host sensor, while the chemosensor also has a strong affinity for AcO- by virtue of the formation of a hydrogen-bonded complex. Intramolecular charge transfer （ICT） causes the colorimetric signaling of compound 1 after interaction with F-/AcO. A study of substituent effects suggested that the O/NH- and O/S-substituted derivatives are also expected to be promising candidates for chromogenic F3AcO chemosensors.

Fluorescent Chemosensing Properties of New Isoindoline Based-Receptors towards F^-and Cu²⁺Ions

Two simple colorimetric and fluorescent anion chemosensors based on amide moieties, 4-nitro-N-[(1,3-dioxoisoindolin-2yl)benzamide (1), 3,5-dinitro-N-[(1,3-dioxoisoindolin-2yl)benzamide (2) have been synthesized and characterized. Comparing with other anions studied, the UV-visible absorption spectrum in DMSO shows significant response toward F- ion with high selectivity, and meanwhile color change is observed from colorless to pink and violet for 1 and 2 respectively in the presence of tetrabutylammonium fluoride (TBAF) (5 × 10-3 M). Moreover, F--induced color changes remain the same even in the large excess of Cl- , Br- and I-. In addition, the 1H NMR spectrum titration in DMSO-d6 shows deprotonation of the receptors 1 and 2 in the presence of basic F- ion. In particular, addition of F- to the receptors 1 and 2 resulted in an enhancement in fluorescence intensity at 770 nm. Both receptors 1 and 2 exhibit a fluorescent emission enhancement when addition of Zn2+, Ni2+, Co2+, Cu2+ and Mn2+ metal ions. The fluorescent enhancement values for the receptor 1 are 2.29 (Cu2+), 1.85 (Ni2+), 1.37 (Co2+), 1.27 (Mn2+), 1.25 (Zn2+) and for 2, 2.57 (Cu2+), 1.66 (Ni2+), 1.36 (Co2+), 1.15 (Mn2+), 1.09 (Zn2+). The selectivity of Cu2+ is higher for 1 and 2 than other metal ions such as Zn2+, Ni2+, Co2+ and Mn2+.

Fluorescence Enhancement of Polyamine Derivatives of 1,8-Naphthalimide with Transition Metal Ions

A series of fluorescent chemosensors 1-3 were synthesized to detect transition metal ions. At the room temperature, fluorescence intensities of these chemosensors in acetonitrile without transition metal ions were found to be very weak, due to the process of the efficient intramolecular photoinduced electron transfer （PET）. However, after addition of the transition metal ions, the chemoscnsor 1-3 exhibits obvious fluorescence enhancement. Moreover, the intensity of the fluorescence emission of chemosensors increases significantly in the presence of Zn^2＋ and Cd^2＋. The fluorescent chemosensors with different polyamine as receptors show diverse affinity abilities to the transition metal ions and signal the receptor-metal ion interaction by the intensity change of fluorescence emission.

A Quinoline Derivated Chemosensor for Cu^(2+) Recognition

A quinoline derivative N-（2-hydroxyl-naphthylmethyl）-N-（quinol-8-yl）amine（2） was synthesized and characterized, which can selectively recognize Cu^2＋ over other metal ions such as Zn^2＋, Cd^2＋, Sn^2＋, Pb^2＋, Hg^2＋, Ni^2＋, Mg^2＋, Cr^3＋, Mn^2＋, Sr^2＋, K^＋, Ca^2＋, Na^＋, Ba^2＋ in acetonitrile/water（volume ratio 99：1）. Cu^2＋ induced a new absorption peak at 464 nm in the absorption spectrum（ε=4.66×10^2 L·mol^-1·cm^-1） and quenched the fluorescence emission of quinoline derivative 2. The binding of quinoline derivative 2 to Cu^2＋ was in 1 ： 1 model and stable constant was esti- mated to be 2.48×10^5 L·mol^-1.

Novel fluorescent chemosensor for Ag^+ based on coumarin fluorophore

A novel chemosensor 1 （CS1） bearing one coumarin and two carbodithioate groups was synthesized and its fluorescent sensing behavior toward metal ions was investigated. Ag^＋ addition to a CH3COCH3/H2O （3：7, v：v） solution of CS1 gave a significantly quenched fluorescence. Other ions including Pb^2＋, Zn^2＋, Cu^2＋, Ca^2＋, Cd^2＋, Co^2＋, Mg^2＋, Mn^2＋, Hg^2＋, Ag^＋, Ni^2＋ induced no or much smaller spectral changes. This constitutes an ON-OFF Ag^＋-selective fluorescent chemosensor.

Ciliotherapy： a novel intervention in polycystic kidney disease

Background Ciliopathies are a group of diseases associated with abnormal structure or function of primary cilia. Ciliopathies include polycystic kidney disease （PKD）, a pathology associated with vascular hypertension. We previously showed that cilia length regulates cilia function, and cilia function is required for nitric oxide （NO） biosynthesis in endothelial cells. Because patients with PKD show abnormal sensory cilia function, the aim of our current study was to search for a targeted therapy focused on primary cilia, which we refer to as ＇cilio- therapy＇. Methods and Results In the present studies, our in vitro analyses refined fenoldopam as an equipotent and more specific dopa- minergic agonist to regulate cilia length and function. Our in vivo studies indicated that fenoldopam increased cilia length and serum NO thereby reducing blood pressure in a PKD mouse model. Our crossover, multicenter, double-blind and placebo-controlled clinical study further indicated that cilia-targeting therapy showed an overall reduction in mean arterial pressure in PKD patients. Conclusions Overall, our studies provide the first evidence of ciliotherapy as an innovative intervention in patients with abnormal primary cilia.

A fluorescent probe for fluoride ion based on 2-aminopyridyl-bridged calix[6]arene

An 2-anfinopyddyl-bddged calix[6]arene on the upper rim fixed in cone conformation （3） was successfully synthesized and its highly selective recognition towards fluoride ion was proved by fluorescent and 1H NMR titration experiments.

A highly selective and sensitive fluorescent chemosensor for Zn^(2+)

A new selective Zn^2＋ fluorescent chemosensor, o-vanillin-4-ethoxybenzoylhydrazone （1）, was designed and prepared. Free 1 mainly displayed very weak fluorescence at 480 nm upon excitation at 403 nm. It displayed high selectivity for Zn^2＋ and had a 518- fold fluorescent enhancement upon binding of Zn^2＋, while the other cation ions had only little influence on the fluorescence of 1. Mechanism of enhancement of l＇s fluorescence by Zn^2＋ was briefly discussed.

Phenanthroline-based Fluorescent Chemosensor for Selective Detection of Zn^(2+) in DMF Buffer Solution

A simple ＂off-on＂ fluorescent chemosensor with high selectivity to zinc ions based on 1,10-phenanthro-line receptor dipyrido[3,2-d：2＇,3＇-f]quinoxaline（L） was investigated.The selectivity response of receptor L to zinc ion was demonstrated by UV-Vis absorption and fluorescence spectroscopies in DMF buffer solution.The experiment results show that the fluorescent chemosensor L exhibits the optimum response behavior to Zn2＋ in the range of pH 8.0―9.0 and shows excellent selectivity to Zn2＋ over other cations tested.

A novel selective fluorescent chemosensor for Cu(Ⅱ)

A novel fluorescence enhancement Cu^2＋ chemosensor derived from coumarin was prepared. Emission study found that it exhibits evident Cu^2＋-arnplified fluorescence prior to Co^2＋, Pb^2＋, Mg^2＋, Mn^2＋, Ni^2＋, Zn^2＋, Fe^3＋, Ag^＋ and Cd^2＋, and the largest emission enhancement factor is about 9 at a ratio of 2：1 （chemosensor 1/Cu^2＋）.

Time-resolved Luminescence-based Chemosensor for Fluoride Anion

A new europium complex is descried as a time-resolved luminescence-based sensor for fluoride anion. The sensor is selective even in the presence of intensive background fluorescence.

Conjugated 8-Hydroxylquinoline-Based Fluorescent Chemosensor for Zn^(2+) and Cd^(2+) and Bioimaging Application in Living Cells

A conjugated 8-hydroxyquinoline( 8-HQ)-based fluorescent chemosensor( 1) for Zinc ion( Zn^(2+)) and Cadmium ion( Cd^(2+)) was developed in aqueous solution and used for Zinc ion living cells bioimaging. The probe 1 was weakly fluorescent,but displayed a strong fluorescence at 580 nm with a large Stokes shift of150 nm in the presence of Zn^(2+) or Cd^(2+). This probe allows the detections of Zn^(2+) in the range of 0. 8-10 μmol/L and Cd^(2+) in the range of 0. 8-8 μmol/L,with the limit of detections of 0. 2 and 0. 6μmol/L for Zn^(2+) and Cd^(2+),respectively. The present probe was successfully used for fluorescence bioimaging of Zn^(2+) or Cd^(2+) in the living cells.

Synthesis of Porphyrin-Appended Pyridine as a Fluorescent Chemosensor for Cd（Ⅱ） and Hg（Ⅱ）

In this research, specific molecular sensors are classified according to the type of receptor-cation interaction, that is ligand-metal interactions. Receptors are based on a multidentate protoporphyrin-appended pyridine platform, which leaves at least a vacant coordination site for the incoming metal ions. A protoporphyrin-appended pyridine, 2,5-pyridine dicarboxyamidyl-8,13-bis（vinyl）-3,7,18,17-tetramethyl-21 H, 23 H-porphyrin（P-PTP）, was designed and synthesized. Its application as potential fluoroionophore for recognition of cadmium and mercury ions is reported. P-PTP shows chelation-enhanced fluorescence effect with Cd（Ⅱ） and Hg（Ⅱ） via the interruption of photoinduced electron transfer （PET） process, which has been utilized as the basis of the fabrication of the metal ions-sensitive fluorescent chemosensor. The analytical performance characteristics of the proposed Cd（Ⅱ）- and Hg（Ⅱ）- sensitive chemosensors were investigated. It shows a linear response toward Cd（Ⅱ） and Hg（Ⅱ） in the concentration range of 1.0×10-3 to 1.0×10-7 M with a limit of detection of 1.0×10-7 M and 0.5×10-7M for Cd（Ⅱ） and Hg（Ⅱ）, respectively. The chemosensor shows good selectivity for Cd（Ⅱ） over a large number of other transition metal ions, i.e., Cu（Ⅱ）, Zn（Ⅱ） and mixed metal ions.

A New Fluorescent Chemosensor for Selective and Sensitive Detection of Mn2+ in Acidic Medium

Recently, fluorescent sensors have attracted considerable attention in their sensitive and selective determination of heavy metal ions in the aqueous acidic medium due to their advantages such as low cost and easy handling. In this study, the bathocuproine (BCP) compound was used as a fluorescent chemosensor. The selectivity and sensitivity of BCP have been investigated against some metal ions of biological and environmental importance. The results obtained from the ultraviolet-visible region (UV-vis.) and the fluorescence spectroscopy experiments revealed that the BCP sensor showed selectivity and sensitivity only to Manganese (II) ions in the experimental conditions studied. In addition, the binding stoichiometry of BCP and Mn2+ was determined to be 1:1 by the Benesi-Hildebrand method.

Determination of Mercuric Ion in Water Samples with a LED Exciting and CCD Based Portable Spectrofluorimeter

The fluorescent characteristics of a fluorimetric chemosensor for mercuric ion, Hg2+, employing a synthesized Rhodamine 6G derivative, have been analyzed. For that, a portable spectrofluorimeter composed of a 515 nm LED as excitation source, two fiber-optics and a CCD camera as detector, has been used, intended for “in situ” analysis. A highly selective Rhodamine based probe for Hg2+, that is water soluble and gives a positive response upon analyte binding, is reported. The reagent is bearing a monothiospirolactone group in a Rhodamine 6G architecture and the thiol atom served for the direct attack of thiophilic Hg2+. The fluorescence enhancement is attributed to the spirolactone ring opening and the coordination of two sulphur atoms to Hg2+ giving a 2:1 reagent: Hg2+ stoichiometry complex.