Design And Synthesis Of Small Molecular Fluorescent Probes For Thiols And Selenols And Their Application In Bioimaging

Fluorescent probe has been widely used in diverse fields such as chemistry,biology,environment,pharmacy and clinical medicine due to its simple operation,facile synthesis,high sensitivity,and good selectivity.Fluorescent probe combined with fluorescence imaging technology,which has real-time monitoring,light damage to biologic samples and visual monitoring,has developed as an essential detection tool to investigate biomolecules in modern life science community.At present,small molecule fluorescent probes used for detection of various analytes have been reported in the literature,and their design,synthesis and analysis methods have become increasingly mature.However,absorption and emission peaks of most fluorescent probes were in the ultraviolet or visible light range,resulting in relatively strong fluorescence background signal,which limits their further application in research of bio-imaging in living animals.In contrast,fluorescence probe with the absorption and emission wavelengths in the near infrared region(650-900 nm),can be well applied in animal tissues and in vivo imaging,due to the characteristics such as of minimum photo-damage to biological samples,deep tissue penetration,and minimum background from auto-fluorescence interference in the living systems.Therefore,in this thesis,using long wavelength xanthene dyes as fluorescence reporting unit,we proposed a strategy for design fluorescent probes with low background fluorescence for detection of thiophenol and selenol,the specific work is as follows:(1)By using two known NIR Chromenylium-Cyanine dyes as fluorophore and nitrobenzenesulfonyl or nitro phenyl ether groups as recognition sites,we systhesized seven near infrared fluorescent probes for the detection of thiophenol.The best performance of the probe CCP-1 was screened out through comparing the selectivity and sensitivity on detection of thiophenols under physiological conditions.Probe CCP-1 could not only detect thiophenol in vitro,and it was successfully visualized thiophenols in vivo.In addition,CCP-1 was used in study the distribution of thiophenols in mice exposed to thiophenols atmosphere,and the experimental results indicated that the levels of thiophenols increased in varying degrees in the liver and lungs in poisoned mice.(2)Using hydroxymethyl rhodamine as fluorescence reporting group,We rationally designed and synthesized fluorescent probe Rhod-Sec with ultralow background fluorescence.Rhod-Sec exhibited "zero" background fluorescence with non-fluorescent spirocyclic under physiological conditions(PBS buffer,pH 7.4).Notably,in the presence of selenocysteine,the fluorescence signal enhanced more than 380-fold.The probe is well suitable for detecting and imaging both exogenous and endogenous selenol in living cells,and it can be successfully applied to visualize the selenol level as a result of LPS-induced cells oxidation resistance for the first time.