Search

In this work, a label-free, selective, and sensitive luminescent sensing platform was established for tyrosinase (TYR) activity monitoring and its inhibitor screening using one kind of lanthanide coordination polymer nanoparticles AMP-Tb/Ag + . By taking advantage of the specific binding and redox properties of Ag + incorporated into the AMP-Tb network and dopamine (DA) as the product of the model substrate tyramine, the enzymatic reaction and the signal change of the sensing platform was effectively linked. The cooperative effect of a weakened energy transfer from AMP to Tb 3+ by altering the electronic structure of Ag + and an efficient photoinduced election transfer (PET) process caused by dopaquinone facilitated the luminescence quenching of Tb 3+ . Thus, this luminescent sensing platform could be employed for quantitative evaluation of TYR activity. There was a good linear range for TYR activity from 0.08 to 0.20 U mL - 1 with a low detection limit of 0.004 U mL - 1 . Furthermore, this assay was successfully applied to accurate determination of TYR activity in human serum samples and efficient screening of TYR inhibitors. Considering unique spectral characteristics of lanthanides along with operation simplicity and superior analytical performance, this sensing platform is very promising in clinical diagnosis and drugs screening for TYR-associated diseases., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier B.V. All rights reserved.)

We report a highly sensitive fluorescent probe based on p-dimethylaminobenzoyl derivatives (probe L) for the detection of Cu 2+ and Zn 2+ . In this work, the probe L exhibited a fluorescent turn-on sensing model to Cu 2+ and Zn 2+ with a distinct fluorescent color change from colorless to green and yellow respectively. Probe L exhibited high selectivity as a fluorescent Cu 2+ /Zn 2+ probe with a limit of detection (LOD) of 45 nM/17 nM. The results of 1 H NMR titrations revealed that the response of L to Cu 2+ and Zn 2+ was triggered by the interaction of the thiophene unit and the metal ion. Furthermore, the fluorescence titrations and Job's plot curves displayed the binding ratio of 1:2 for Cu 2+ and 1:1 for Zn 2+ metal-L complex formation respectively. Density functional theory calculation also demonstrated the possibility of molecular luminescence and the process of metal-L complex formation. Additionally, fluorescent test strips have been prepared for convenient detection of Cu 2+ and Zn 2+ , which means the convenient and rapid assay in real samples can be achieved., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In this work, a simple and easily synthesized Schiff-based derivative colorimetric and fluorescent sensor (1), 4-dimethylamino-benzoic acid (2-imidazole formaldehyde)-hydrazide, was obtained for the detection of Cu 2+ and S 2- . The compound 1 exhibited dual spectral responses to Cu 2+ , that is, vivid color change and fluorescence enhancement in the presence of Cu 2+ . The detection limits were valued as 0.46 μM and 15 nM according to absorption and fluorescent response, respectively. Both of them are below the World Health Organization (WHO) guidelines for drinking water (31.5 μM). In addition, the ensemble (1-Cu 2+ ) selectively and sensitively detected a low concentration of S 2- . As the addition of S 2- instantly removed Cu 2+ from the ensemble (1-Cu 2+ ) resulting in a color change from yellow to colorless and a "turn-off" fluorescent response. The detection limit for S 2- was estimated as 0.12 μM (from fluorescent method) and 0.68 μM (from absorption method), respectively, each of which was also lower than the maximum allowable level of S 2- (15 μM) in drinking water defined by the WHO. The binding process was confirmed via UV-vis absorption, fluorescence measurements, 1 H NMR, mass spectroscopy and density functional theory calculation. What's more, successful practical application of test paper is used to inspect the S 2- which means the convenient and rapid assay in real samples can be achieved., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A new p-dimethylaminobenzamide derivative based compound BDIH has been synthesized. Cu 2+ turned on the fluorescence of compound BDIH with a 1:2 binding stoichiometry. The fluorescent color of compound BDIH shows an evident change from colorless to bright blue upon the addition of Cu 2+ , which could be visibly detected by the naked eye under UV light at 365nm. More importantly, the detection limit was found to be 0.64nM which is far lower than the maximal allowed concentration of the WHO limit (31.5μM) for drinking water. This selective "turn-on" fluorescence sensor was used to identify Cu 2+ in living cells using confocal fluorescence microscopy, indicating that compound BDIH has a potential application for selective detection of Cu 2+ in organism., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A new compound, 2-boronobenzaldehyde-(2'-hydroxyl-4'-sulfonic acid) naphthalene hydrazone (1), was synthesized and its structure was characterized by proton nuclear magnetic resonance, mass and element analyses. The presence of Pb(2+) led 1 to undergo colorimetric and fluorescent changes, which were detectable with the naked eye. Thus, a dual spectral response for Pb(2+) detection was introduced. In KH2PO4-NaOH buffer aqueous solution (pH 6.0), 1 exhibited fluorescence enhancement at 568 nm and hyperchromicity at 595 nm upon the addition of Pb(2+). The fluorescent intensity change was proportionate to the concentration of Pb(2+) with a dynamic working range of 5.0×10(-7) mol L(-1) to 1.0×10(-4) mol L(-1) and a detection limit of 3.7×10(-8) mol L(-1). The fluorometric method was successfully applied for the detection of Pb(2+) water of Qianhu Lake and soil in Nanchang university campus. The recoveries were 111-116% for water and 97.6% for soil respectively, determined via the standard addition method., (Copyright © 2013 Elsevier B.V. All rights reserved.)

A new compound, 2,5-di-[2-(4-hydroxy-phenyl)ethylene]-terephthalonitrile (DHPEPN), was synthesized. The interaction between bovine serum albumin (BSA) and DHPEPN in Tris-HCl buffer solution (pH 7.4) was investigated using fluorescence and UV-vis absorption spectroscopy. The mechanism of BSA fluorescence quenched by DHPEPN is discussed according to the Stern-Volmer equation. The binding constant and the thermodynamic parameters ΔH, ΔS, ΔG at different temperatures were calculated. The results indicate that the van der Waals interaction and hydrogen bonding play major roles in the binding process. The distance between BSA and DHPEPN is estimated to be 3.59 nm based on the Förster resonance energy transfer theory. The spectral changes of synchronous fluorescence and three-dimensional fluorescence suggest that both of the microenvironment of DHPEPN and the conformation of BSA are changed during binding between DHPEPN and BSA., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A novel ditopic chromogenic receptor, N-5-(8-hydroxy)quinoline-N'-4'-nitro-phenyl thiourea (1), was synthesized. The metal complex 1-Hg(2+) showed sensitive and highly selective responses to F(-) over other anions such as CH(3)CO(2)(-), H(2)PO(4)(-), HSO(4)(-) and Cl(-). 1-Hg(2+)-F(-) complex formed, which promoted the intramolecular charge transfer and led to a dramatic spectral change. The color of 1-Hg(2+) solution changed from colorless to red upon addition of F(-). Thus, a colorimetric assay of F(-) was developed in acetonitrile by naked-eye detection. F(-) behaved linearly in the 8.0 x 10(-6) to 2.0 x 10(-5) mol L(-1) concentration range with LOD as 1.4 x 10(-6) mol L(-1).

The binding characteristics between 2,5-di-[2-(3,5-bis(2-pyridylmethyl)amine -4-hydroxy-phenyl) ethylene] pyrazine (1) or its complex (1-Zn) and serum albumins were studied by fluorescence spectroscopy in pH 7.4 aqueous solution. 1-Zn emitted weak fluorescence at 580 nm in a pH 7.4 Tris-HCl buffer solution when excited at 435 nm, however, the fluorescence intensity increased upon addition of serum albumins with the blue shift of emission peak to 524 nm. The binding constants were estimated as 8.40 x 10(7) and 3.03 x 10(6)mol(-1)L for bovine serum albumin (BSA) and human serum albumin (HSA) respectively, and the number of binding sites was 1 for each. The quenching mechanism of fluorescence of serum albumins by 1-Zn was considered as a static quenching process. The binding distance between 1-Zn and serum albumins and the energy transfer efficiency were obtained based on the theory of Förester spectroscopy energy transfer. The effect of 1-Zn on the conformation of serum albumins was further analyzed using synchronous fluorescence spectrometry. The experiment results clearly showed that 1-Zn is a highly sensitive protein sensor.

A novel colorimetric sensor based on 8-hydroxy quinoline-5-azo-4'-nitrobenzene (1) was prepared and used for recognizing anions. 1 and its metal complex (1.Co) were found to show response to anions such as CH(3)CO(2)(-), H(2)PO(4)(-), HSO(4)(-), F(-) and dramatic color changes were observed. The selectivity and sensitivity of 1 and 1.Co for sensing anions were different, which was in the order of CH(3)CO(2)(-)>F(-)>H(2)PO(4)(-)>>HSO(4)(-) for 1 and H(2)PO(4)(-)>HSO(4)(-)>CH(3)CO(2)(-) approximately F(-) for 1.Co, respectively. In CH(3)CN, sensor 1.Co exhibited excellent specificity toward H(2)PO(4)(-), and the color variety was dependent on the concentration of H(2)PO(4)(-) which was attributed to anion structure and stability of anionic complex (1-anion), metal complex (1-Co) and inorganic complex (Co-anion).

A structurally simple colorimetric sensor, N-4-nitrobenzene-N'-1'-anthraquinone-thiourea (1), for anions was synthesized and characterized by (1)H NMR, ESI mass and IR methods. In acetonitrile, the addition of F(-) changed 1 solution from colorless to yellow. In the presence of other anions such as CH(3)CO(2)(-), H(2)PO(4)(-), HSO(4)(-) and Cl(-), however, the absorption spectrum of 1 was slightly red shifted with no obvious color changes observed. The association constants of anionic complexes followed the order of F(-)>>CH(3)CO(2)(-)>H(2)PO(4)(-)>HSO(4)(-)>Cl(-)>Br(-), which was different from the order of anion basicity. AM1 calculation results indicated that the most stable configuration of 1 existed in the Z-E-conformation with a six-membered ring via intramolecular hydrogen bond. This made thiourea moiety of 1 in an unfavorable conformation to bond with oxygen-anionic substrates such as CH(3)CO(2)(-) and H(2)PO(4)(-), thus leading to a high selectivity and sensitivity for the detection of F(-).