Design,Synthesis And Bioimaging Applications Of ROS Fluorescence Probes

ROS are produced intracellularly through multiple mechanisms during the metabolism process.Since the oxidation state of oxygen in ROS ranges from 2-to 0,ROS are highly reactive and are considered as one of the keyregulatory molecules for cells.ROS can not only eliminate undesirable xenobiotics but also have great effects on cell signaling,which is vital for the regulation of physiological and pathological processes.Hydrogen peroxide?H₂O₂?and hypochlorous acid?HClO?are two important active oxygen species,which are higher in content than other reactive oxygen species and participate in many physiological processes.However,excessive amounts of H₂O₂ and HClO can induce the development of various diseases such as cancer and cardiovascular diseases.Fluorescent probes have advantages of simple operation,good selectivity,low cost and can be combined with biological imaging technology to detect enzymes and biological molecules in vivo.Therefore,the development of specific and sensitive fluorescent probes is particularly important for the detection of ROS.In this paper,we synthesized a fluorescent probe for detecting H₂O₂ based on a oxonium ring derivative fluorophore,a fluorescent probe for detecting ClO^-based on a pyran-coumarin fluorophore,and a two-photon fluorescence probe for detecting HClO based on a naphthalimide fluorophore.In chapter 2,describes a novel red-emissive fluorescence probe?RhoB?for the visualization of H₂O₂ in living cells,tissues and animals.RhoB was constructed on the base of a xanthene-based red-emissive dye and displayed nearly no fluorescence.After the treatment with H₂O₂,RhoB can exhibit red fluorescence with the emission wavelength at 638nm.RhoB exhibited highly sensitive and selective response to H₂O₂.RhoB was successfully applied for imaging of exogenous and endogenous H₂O₂ in living cell,can also be utilized for visualizing H₂O₂ in living tissues and animals.In chapter 3,describes a unique ratiometric fluorescent probe?CBP?with an extremely large emission shift for detecting hypochlorite in living cells.Utilizing positively charged?,?-unsaturated carbonyl group as the reaction site,the probe CBP itself exhibited near-infrared?NIR?fluorescence at 662 nm,and can display strong blue fluorescence at 456nm when responded to hypochlorite.Notably,the extremely large emission shift of 206 nm could enable the precise measurement of the fluorescence peak intensities and ratios.CBP showed high sensitivity,excellent selectivity,satisfactory performance at physiological pH,and low cytotoxicity.The bioimaging experiments demonstrate the biological application of CBP for the ratiometric imaging of hypochlorite in living cells.In chapter 4,presents a novel ER-targeting turn-off fluorescent probe?NHS-ER?for the two-photon detection of HClO in living cells,for the first time.The probe was constructed on the base of naphthalimide and showed strong green fluorescence.In response to HClO,the fluorescence intensity at 502 nm gradually decreased,and the probe showed excellent selectivity to HClO.In addition,the probe NHS-ER showed ER-targeting property and could be successfully applied to the two-photon imaging of HClO in living cells.