ICT Mechanism And Two-photon Applications Of Carbazole And Phenothiazine Derivatives

Using the two-photon microscopy (TPM) technology, which employs two near-infrared photons as the excitation source, has become important in bioimaging applications. Thus TPM has the advantage of offering reduced phototoxicity, increased specimen penetration, localized excitation, and prolonged observation time. Its application detection of reactive oxygen, pH, temperature and the fluorescent labeling of nucleic acids, proteins and other biological molecules has become the focus of attention. This thesis is focused on the synthesis and biological applications of carbazole and phenothiazine-based derivative using intramolecular charge transfer principle.Cellular viscosity is known to influence how biomolecules and chemical signals interact and are transported within live cells, and consequently abnormal changes in cellular viscosity are related to cellular aspects of many diseases and malfunctions. So, it is very meaningful to develop excellent two-photon fluorescent probes for the viscosity. In the present investigation, we report four carbazole-based fluorescent sensors KQ、Caz-Cy2、Qcaz-Cy2and Pcaz-Cy2. The fluorescence emission peak of these dyes is in the red light region, they shown very low fluorescence and quantum yield in non-viscous solvents, and was not apparently affected by solvent polarity. We focused on the Caz-Cy2and Qcaz-Cy2, which showed a different fluorescence enhancement at two emission bands with increases of the solvent viscosity. Compared to the blue emission band, the red emission band of Caz-Cy2and Qcaz-Cy2rose much faster as solvent viscosity was increased. Moreover, the logarithm of fluorescence ratio thereof (Ired/Iblue) had a linear relationship with that of the viscosity of the solution. The two-photon absorption spectra of Caz-Cy2increased about20-fold,μ which was achieved by increasing the proportion of glycerol in the water. Caz-Cy2and Qcaz-Cy2is an excellent TP rotor sensor candidate which appears to be reporting on the viscosity of mitochondria in live cells as well as in living tissues at depths of60-190μm by ratiometric fluorescence imaging.Reactive oxygen species (ROS) play crucial roles in various physiological and pathological processes. ROS are produced endogenously from oxygen, mainly by the mitochondrial electron transport chain, and play a significant role in eliminating undesirable xenobiotics. Based on the difficulies which we mentioned in the preceding, we reported two phenothiazine-based fluorescent sensors, PTE-Cy2and PCE-Cy2. Oxidation by highly reactive oxygen species (hROS) involves attack at the thiazine sulfur atom and destruction of the π conjugation of the cyanine moiety. The HPLC and MS analysis of the test solutions confirmed that the flourescence products of the reaction of probe PTE-Cy2and PCE-Cy2with ROS. Dual fluorescence emissions are enhanced dramatically at λem470nm and595nm. PTE-Cy2served as a ratiometric and "naked-eye" sensor for detecting hROS and PCE-Cy2 only shown selectivity for Hydroxyl radicals over other oxidants. The flourescence products of the reaction of probe PCE-Cy2with Hydroxyl radicals was POCE-Cy2. The two-photon absorption spectra of POCE-Cy2increased as solvent viscosity was increased. PCE-Cy2being particularly sensitive to ROS in mitochondria, with the fluorescent reaction products being substantially retained in these organelles. This is as expected for PCOE-Cy2since this dye, like PCE-Cy2, is a lipophilic cation and is thus expected to localize in mitochondria. POCE-Cy2is an excellent TP rotor sensor candidate which appears to be reporting on the viscosity of mitochondria in live cells as well as in living tissues at depths of60-130μm by ratiometric fluorescence imaging.Based on the high electron density characteristics of carbazole and phenothiazines, we designed and synthesized six dyes by ethynyl and vinyl connecting naphthalimide and terpyridine groups. CaNP and CaTNP were quenching two-photon probes for zinc and cadmium ion. NSPA-Zn and NSPOA-Zn were resulting fluorescent sensors for pyrophosphate in the solution. We focused on the NSPA-Zn and NSPOA-Zn, which showed a different fluorescence enhancement at two emission bands (λem475nm and605nm) with increases of the pyrophosphate. The two-photon absorption spectra of NSPA-Zn increased to175GM from28GM, which was recognizing to phosphate selective interference of other anions. The NSPOA-Zn belongs to ICT sensor, when combined with pyrophosphate, the binding force of the terpyridine and zinc ion was weakened and the ICT role would decrease. In this process, the fluorescence at λem605nm reduced and the fluorescence emission at λem475nm increased gradually, the two-photon absorption cross section increased to358GM at730nm from210GM at810nm. The NSPA and NSPOA can selective recognize zinc ion in living cells with two-photon fluorescence imaging, but when pyrophosphater added, the initial fluorescence recovered.