Design And Synthesis Of Reaction-based Fluorescent Probes For Hypochlorous Acid And Their Application In Bioimaging

Hypochlorous acid?HCl O?,one of the important reactive oxygen species?ROS?,is faintly acid and it partially dissociates to give the hypochlorite ion in physiological pH solutions.Endogenous hypochlorous acid?HOCl?is usually produced from H₂O₂ and Cl^-by myeloperoxidase.As one of the ROS,HOCl plays an indispensable role in immune systems,but high level of concentration of HOCl can cause a variety of human diseases,such as Type 2 Diabetes Mellitus,cardiovascular diseases,rheumatiod arthritis,neurodegenerative disorders,nephropathies and cancer-related diseases.Thus,the detection of HOCl in living system is of great significance for revealing its physiological and pathological processes.Compared with traditional analytical methods,fluorimetry methods have been largely pursued due to their versatility,simplicity,high sensitivity,fast analysis and non-invasivenss.In this paper,based on the recent development of HClO probes,the novel fluorescent probes were developed for HClO with high selectivity and ultra-sensitivity.Meanwhile,the fluorscencent properties and biological applications of those probes were systematically investigated.The fluorescent probes 1b,2b,3b and 4b have been designed and synthesized based on intramolecular charge transfer process?ICT?mechanism.And the optical properties and the feasibility for biological application of those probes were studied.Based on the ICT mechanism,probes can exhibited remarkable changes of fluorescence according to the different electronic properties of functional group.Herein,the probes 1b,2b,3b and 4b synthesized by the introduction of N,N-dimethylmethanethioamide into 3 bits to coumarin derivatives can detect HClO by the oxidation of sulfur atom of dimethylcarbamothioate.As the absorption and emisson spectrum showed,all probes showed excellent properties for detecting HClO.Furthermore,probe 2b showed an 219-fold enhancement in fluorescence intensity after reacting with HClO.More importantly,the detection limit of probe 2b is0.94 nM.Meanwhile,the probe 2b were selected to image HClO in cells and worms in view of its excellent properties.In this chapter,we further investigated the detection mechanism of fluorescenct probe RO585 for HClO.According to titration experiment of NMR,ESI-MS and optical experiments,we proposed that the detection mechanism of the probe RO585 is covalent-assembly of aromatic hydrazone.And probe RO585 showed high selectivity and ultra-sensitivity for detecting hypochlorite.More importantly,the fluorescence imaging of cells and worms indicated that probe RO585 can be successfully applied in vivo.In addition,we also got the crystal structure of probe RO585.