We synthesized the Ni(II) complexes with dithiocarbamate ligand derived from ortho and para isomers sulforhodamine B fluorophores and demonstrated they are highly selective in reaction with nitrogen dioxide (NO2). Comparing to the para isomer, the ortho isomer showed much greater fluorescence increase upon reaction with nitrogen dioxide, which led to oxidation and de-complexation of dithiocarbamate ligand from Ni(II). We applied this probe for visual detection of 1 ppm nitrogen dioxide in gas phase and fluorescence imaging of NO2 in macrophage cells treated with nitrogen oxide donor.
Herein, we report the development of two fluorescent probes for the highly selective and sensitive detection of H2S. The probes take advantage of a Cu(II)-cyclen complex, which acts as a reaction center for H2S and as a quencher of BODIPY (boron-dipyrromethene)-based fluorophores with emissions at 765 and 680 nm, respectively. These non-fluorescent probes could only be turned on by the addition of H2 S, and not by other potentially interfering biomolecules, including reactive oxygen species, cysteine, and glutathione. In a chemical system, both probes detected H2S with a detection limit of 80 nM. The probes were successfully used for the endogenous detection of H2S in HEK 293 cells, for measuring the H2S-release activity of dietary organosulfides in MCF-7 cells, and for the in vivo imaging of H2S in mice.
A turn-on
fluorescent probe, HOCD-RB, for monitoring singlet oxygen (1O2) was developed by linking rhodamine B as fluorophore
with dimethylhomoocoerdianthrone (HOCD) as 1O2 reaction site and fluorescence quencher due to the intramolecular
energy transfer (ET) between rhodamine B and HOCD moieties. Upon exposure
to 1O2 it rapidly forms endoperoxide with HOCD
and turns on the fluorescence of rhodamine B by 18-fold. Taking advantage
of the HOCD-RB probe that shows fast response, high sensitivity, and
selectivity for 1O2, it is applied for imaging
of endogenous 1O2 in living cells and the fluorometric
assay for evaluating 1O2 quenching activity
of selected common flavonoids found in our daily diets. The results
show that the 1O2 scavenging activity of flavonoids
depends on not only the structure of individual flavonoid but also
the competitive interactions between mixed flavonoids. The best antioxidant
capacity for individual and mixed flavonoids is epigallocatechin gallate
and the mixture of catechin gallate with kaempferol, respectively.
Overall, this work provided a new tool for detection and imaging of
singlet oxygen activity in a biological system as well as an efficient
fluorometric assay of 1O2 scavenging activity.
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