A selenolactone-based fluorescent chemodosimeter to monitor mecury/methylmercury species in vitro and in vivo

Sensing performance enhancement via acetate-mediated N-acylation of thiourea derivatives: a novel fluorescent turn-on Hg(2+) chemodosimeter

A Hg(2+) chemodosimeter P3 derived from a perylenebisimide scaffold and thiourea fragments was systematically studied with focus on the photophysical, chemodosimetric mechanistic, as well as fluorogenic behaviors toward various metal cations for the sake of improving selectivity to Hg(2+). As demonstrated, Hg(2+) can promote a stepwise desulfurization and N-acylation of P3 with the help of an acetate anion (OAc(-)), resulting in an N-acylated urea derivative. Interestingly, OAc(-) has the effect of improving the selectivity of P3 to Hg(2+) among other metal ions; that is, in an acetone/Britton-Robinson buffer (9:1, v/v; pH 7.0) upon excitation at 540 nm, the relative fluorescence intensity is increased linearly with increasing concentration of Hg(2+) in the range of 2.5-20 μM with a detection limit of 0.6 μM, whereas the fluorescence intensity of P3 to other metal ions, including Na(+), K(+), Mg(2+), Ca(2+), Mn(2+), Fe(2+), Ni(2+), Co(2+), Zn(2+) Ag(+), Cd(2+), Pb(2+), and Cu(2+), is negligible. The fluorescent bioimaging of chemodosimeter P3 to detect Hg(2+) in living cells was also reported.

A new fluorescent chemosensor for Hg2+ in aqueous solution

We prepared an aminothiourea-derived Schiff base (DA) as a fluorescent chemosensor for Hg(2+) ions. Addition of 1 equiv of Hg(2+) ions to the aqueous solution of DA gave rise to an obvious fluorescence enhancement and the subsequent addition of more Hg(2+) induced gradual fluorescence quenching. Other competing ions, including Pb(2+), Cd(2+), Cr(3+), Zn(2+), Fe(2+), Co(3+), Ni(2+), Ca(2+), Mg(2+), K(+) and Na(+) , did not induce any distinct fluorescence changes, indicating that DA can selectively detect Hg(2+) ions in aqueous solution.

Recognition of Hg2+ and Cr3+ in physiological conditions by a rhodamine derivative and its application as a reagent for cell-imaging studies

A new rhodamine-based receptor, derivatized with an additional fluorophore (quinoline), was synthesized for selective recognition of Hg(2+) and Cr(3+) in an acetonitrile/HEPES buffer medium of pH 7.3. This reagent could be used as a dual probe and allowed detection of these two ions by monitoring changes in absorption and the fluorescence spectral pattern. In both instances, the extent of the changes was significant enough to allow visual detection. More importantly, the receptor molecule could be used as an imaging reagent for detection of Hg(2+) and Cr(3+) uptake in live human cancer cells (MCF7) using laser confocal microscopic studies. Unlike Hg(ClO(4))(2) or Hg(NO(3))(2) salts, HgCl(2) or HgI(2) failed to induce any visually detectable change in color or fluorescence upon interaction with L(1) under identical experimental conditions. Presumably, the higher covalent nature of Hg(II) in HgCl(2) or HgI(2) accounts for its lower acidity and its inability to open up the spirolactam ring of the reagent L(1). The issue has been addressed on the basis of the single-crystal X-ray structures of L(1)·HgX(2) (X(-) = Cl(-) or I(-)) and results from other spectral studies.

Multimode selective detection of mercury by chiroptical fluorescent sensors based on methionine/cysteine

Two multimode Hg(II) sensors, L-MethBQA and L-CysBQA, were obtained by fusing methionine or S-methyl cysteine, into a bis-quinolyl amine-based chiral podand scaffold. Quinolyl groups serve as the fluorophore and possess nitrogen lone pairs capable of chelating metal ions. On exposure to Hg(2+) or Zn(2+), these sensors show signal enhancement in fluorescence. However, Cu(2+) quenches their fluorescence in 30:70 acetontrile/water. L-CysBQA complexes with Hg(2+), producing an exciton-coupled circular dichroism spectrum with the opposite sign to the one that is produced by Cu(2+) or Zn(2+) complexation. L-CysBQA binds Hg(2+) more strongly than Zn(2+) and is shown to differentiate Hg(2+) from other metal ions, such as Zn(2+), Cu(2+), Ni(2+), and Pb(2+), exceptionally well. The synergistic use of relatively soft sulfur, quinoline-based chiral ligands and chiroptically enhanced fluorescence detection results in high sensitivity and selectivity for Hg(2+).

Zebrafish as a good vertebrate model for molecular imaging using fluorescent probes

Fluorescent probes have been used extensively to monitor biomolecules and biologically relevant species in vitro and in vivo. A new trend in this area that has been stimulated by the desire to obtain more detailed information about the biological effects of analytes is the change from live cell to whole animal fluorescent imaging. Zebrafish has received great attention for live vertebrate imaging due to several noticeable advantages. In this tutorial review, recent advances in live zebrafish imaging using fluorescent probes, such as fluorescent proteins, synthetic fluorescent dyes and quantum dots, are highlighted.