The Novel Organic Fluorescent Probes For Imaging Detection Of Bioactive Species

Hypochlorous acid is an important bioactive species and an serve as key indicators in various physiological and pathological processes.Abnormal levels of hypochlorous acid could cause damage of tissue.Therefore,timely and dynamic monitoring of hypochlorous acid in living organisms is extremely important for biological health.The organic small-molecule fluorescent probe has the advantages of good selectivity,sensitivity and cell permeability.Therefore,it has become an ideal method for intracellular molecular detection.On the base of previous studies,we have designed and synthesized four fluorescent probes to highly detect hypochlorous acid.And we have systematically studied their fluorescence properties and biological applications.In chapter 1,we briefly introduced the research background and luminescence mechanism of fluorescent probes.We also summarized the recent research progress of fluorescent probes for hypochlorous acid detection.At the same time,we described the significance of the research in this paper.In chapter 2,based on the mechanism of photoinduced electron transfer(PET),the fluorescent probe NBD-DOP for hypochlorous acid detection was designed and synthesized.The probe consists of 4-chloro-7-nitro-benzofuraza and a dopamine moiety that reacts with hypochlorous acid specifically.The dopamine group could effectively quench the fluorescence of molecule by the PET effect.Experimental data showed that NBD-DOP could detect hypochlorous acid with ultra-fast response,high sensitivity and selectivity on a wide pH range of solution.The probe could be used to detect the production of hypochlorous acid by MPO,and has been applied in the imaging of exogenous and endogenous hypochlorous acid in living cells by confocal fluorescence microscopy.In chapter 3,we designed and synthesized two ultrasensitive hypochlorous acid fluorescent probes,Naph-1 and Naph-2,based on mechanism of intramolecular charge transfer(ICT).The fluorescent groups of the probe are 6-hydroxy-2-naphthalaldehyde and 6-acetyl-2-naphthol,respectively.The recognition group is thiocarbamate group.The experimental data showed the ultra-sensitive of probe,because the fluorescence multiple was enhanced by 4600-fold after the probe reacting with hypochlorous acid in the aqueous buffer solution,and the detection limit was 2.37 nM.At the same time,experiments have shown that the probe is highly specific to hypochlorous acid,rapid response and biologically low toxicity.Most importantly,the probe was successfully used for the detection of exogenous hypochlorous acid in Hela cells and 4T1 cells and the fluorescence imaging of endogenous hypochlorous acid in RAW 264.7 macrophages.In chapter 4,a ratiometric fluorescent probe TR-OCl for hypochlorous acid detection was designed and synthesized,which based on the principle of aggregation induced emission and dark-pass energy transfer.The probe uses tetraphenylethene as a dark energy donor and rhodamine B thiohydrazide as an energy acceptor.The dark through-bond energy transfer has advantages such as independent spectral overlap and high energy transfer efficiency,thus avoiding the emission leakage form the donor dyes.The experimental data showed that TROCl could detect hypochlorous acid with fast response,high sensitivity and high selectivity in a wide pH range.The probe's fluorescence ratio multiple is enhanced by 7000-fold after the reaction of hypochlorous acid,and the detection limit was 1.29 nM.Lastly,the successful result of HOCl imaging detection in different cell line indicates the potential use of the probe in living systems.