Fluorescent Properties And Cell Imagings Study Of Reaction-based Fluorescent Probes For Hypochlorous Acid

Among reactive oxygen species?ROS?,hypochlorous acid?HOCl?has received special attention for its pivotal influence in physiological and pathological environments.Fluorescence probe has been widely used for the detection of ROS and cell imaging due to its excellent temporal and spatial resolution capability,and reaction-based fluorescence probes have got much attention for fluorescence probes design because of its high sensitivity and selectivity.Thus,it is urgently required for the development of fluorescent probes and the study of cell imaging for sientific and pactical value which has become one of the most active and interesting areas in ROS detection.In this dissertation,the HOCl detecting fluorescent probes with high sensitivity and selectivity have been designed and developed by photoinduced electron transfer?PET?and intramolecular charge transfer?ICT?mechanism using the HOCl oxidation of phenothiazine group based on the summarize of recent development in such fluorescent probes,and the fluorescence property and cell imaging of these probes have been studied systematically.The novel fluorescence probes based on photoinduced electron transfer?PET?mechanism have been designed and synthesized,and the optical properties and cell imagings have been studied.The turn-on fluorescent probes PTZ-AO1,PTZ-QL1 and PTZ-QL2 have been designed and synthesized by the strong oxidant property of HOCl in which phenothiazine is chosed as electron donor because of its higher electron cloud density,and acridine orange and cyanine are designed as reporter group for its high quantum yields and good photostability.PTZ-AO1 functioned as a highly HOCl-selective with a fast?within 5 s?and sensitive response with good photostability,solubility and the detection limit of 2.7 nM,and exhibited excellent properties as HOCl-specific fluorescent probe.With the probe PTZ-AO1,we successfully conducted exogenous,endogenous and real-time imaging of HOCl by systematical cell imaging study.Then a reversible chemodosimeter PTZ-AO2 for Cu²⁺ detection based on PET channel was successfully developed.Furthermore,PTZ-AO2 was shown to be a promising potential selective fluorescent chemodosimeter for the direct quantitative measurement of residual copper species in drug chemicals.The new sensors PTZ-QL1 and PTZ-QL2 have been developed and the fluorescent properties towards HOCl detecting and cell imaging have been studied.They could detect HOCl in PBS solution with long wavelength at 620 nm and were then applied to image HOCl in living cells.The fluorescence probes based on intramolecular charge transfer process?ICT?mechanism have been designed and studied,and the optical properties and cell imagings have been studied.As the weak change of electronic properties of functional group could lead to the absorption and fluorescence signal changes,phenothiazine is chosed in the building block based on the oxidation of the sulfur atom by HOCl.Then,the probes PTZ-CY1,PTZ-CY2 and PTZ-CY3 have been designed and synthesized based on ICT mechanism.The spectra and cell imaging property were studied.These probes exhibited maximum emission at 595 nm,showed good selectivities towards HOCl over other ROSs with good solubility and wide pH range,and could image HOCl in living cells.Finally,PTZ-CY4 and PTZ-CY5 which contained triphenylphosphonium?TPP?and morpholine moiety respectively were designed.Both probe showed good selectivities towards HOCl and fluorescence properties of PTZ-CY5 in viscous solvent were studied.Further work is going on by exploiting dye PTZ-CY5 as new probes in hypochlorite detecting in the mitochondria target living cells and will be reported in due course.The novel rhodol derivatives with two spirorings have been designed and studied via a Friedel-Crafts acylation based on fluorescein.It was interesting to note that the fluorophore of this novel dye was composed of five fused six-membered rings and its structures convertied between spirolactone isomers with non-fluorescent optical signals and spiroring-opened isomers with fluorescent optical signals.Its reversible structural conversions among the monocation,neutral,monoanion forms under different conditions were investigated in detail by electronic absorption and fluorescence emission spectroscopy analysis.From strong acidic environment?6 mol/L HCl?to pH 4,the structures were the double ring-opened form A or B.With the pH increased to ca.4,the neutral bispirolactone C was the dominate structure.However,the dye was converted to the single ring-opened form G or H in basic conditions from pH 4 to strong basic conditions?5 M NaOH?.Then,the extended chemical modifications were studied and the derivatives Rho2,Rho3 and Rho4 were obtained.Finally,the dye Rho1 was converted to a thiosemicarbazide spirolactam Rho7 which turned out to be a highly Hg²⁺-selective fluorescent probe.