Fluorescent Probes For Gasotansmitters Nitric Oxide And Sulfur Dioxide Derivatives

Due to the simplicity, inexpensiveness, sensitivity, selectivity, especially nondestructive imaging of targeted biomolecules in live cells or tissues, organic small molecular fluorescent probes become as one of the most powerful tools and have been widely applied in biological, environmental, and medical science. Nitric oxide, carbon monoxide and hydrogen sulfide are known as toxic gases, but recently research shown that they are endogenously produced gaseous molecules and play many important biological and physiological roles. Sulfur dioxide is a well-known air pollutant, which can be generated endogenously and exhibites unique bioactivities. It is speculate that SO₂ can be considered a gasotransmitter, just as NO, CO and H₂S. However, the detailed mechanisms by which these gasotransmitters exert their biological functions still remain elusive. Thus, it is important to develop sensitive and selective fluorescent probes for these gasotransmitters.In Chapter 2, a mitochondria-specific fluorescent probe 2-1 was exploited for the detection of NO by the direct conjugation of pyronin dye with one of amino of o-phenylenediamino unit. The probe could selectively detect NO over DHA, AA, MGO as well as reactive oxygen/nitrogen species with significant off-on response due to producing the red-emission triazole 2-2. In the presence of Cys/GSH,2-2 could further transform into the green-emission aminopyronin 2-4 and red-emission thiopyronin 2-5, respectively. Assisted by intracellular Cys and GSH, the probe 2-1 demonstrated its potential to monitor mitochondrial NO in a dual-channel mode.In Chapter 3, a fluorescence turn-on probe for bisulfite has been developed by taking advantage of the specific reaction of bisulfite and aldehyde in combination with the hydrogen bond inhibited C=N isomerization mechanism. Probe 3-1 showed weak fluorescent due to the C=N isomerization. The aldehyde group in 3-1 can selectively react with bisulfite and form the aldehyde-bisulfite adducts, which produce a strong hydrogen bond donor, i.e.-OH group. Thus, the C=N isomerization-reduced quenching can be efficiently inhibited by a produced intramolecular O-H…N=C hydrogen bond, leading to recover the fluorescence of 1,8-naphthalimide fluorophore. Probe 3-1 can be used to selective detect bisulfite in weak acid buffer solution, and has been applied to determination of HSO₃^- concentrations in locally granulated sugar.In Chapter 4, a coumarin-hemicyanine dye 4-1 was reported for ratiometric fluorescent detection of SO₂ derivatives HSO₃^- and SO₃^2- based on a novel addition-rearrangement cascade reaction. The nucleophilic attack of HSO₃^- or SO₃^2- toward 4-1 interrupts the ?-conjugation and blocks the ICT process, as a result, two well-separated emission peaks before and after adding HSO3^- or SO₃^2- can be obtained due to the distinct emission between the hemicyanine dye and the produced coumarin dye. Probe 4-1 shows high selectivety toward SO₂ derivertives than common anions, reactive oxygen species ?ROS? and biothiols, such as GSH and Cys. Probe 4-1 has been used to image SO₂ derivatives in HeLa cells.