The Design,Synthesis And Biological Imaging Of A Novel Fluorescent Probe Based On Rhodamine Analogues

Since fluorescent probes are facile,rapid,and selective for analytes,they possess unique advantages in various chemical analysis methods.Rescently,many types of fluorescent probes have been developed on the basis of the photophysical properties of various dyes,and have been more used to interact with biological target molecules,thereby performing various biological phenomena at the molecular level.Fluorescence imaging has become a powerful technique for monitoring various physiological phenomena in living cells and animals at high temporal and spatial resolutions.Fluorescence probe,which combines fluorescent probes with imaging technology,has become an indispensable tool for the visualization of various physiological processes in life.However,for most of the fluorescent probes that have been developed,the emission wavelength is generally in the visible light region,resulting in damage to biological samples,poor tissue penetration,and fluorescence interference from complex biological matrix during bioimaging applications.Therefore,the development of fluorescent imaging probes with excellent properties has become a huge challenge and interest for analytical researchers.Based on the classic rhodamines,this thesis presents a new type of rhodamine analogue fluorescent dyes,which not only retains the advantages of high molar extinction coefficient and good stability,but also enables the emission wavelengths to reach the far-red to near-infrared region.Furthermore,based on the new dyes,targeted fluorescence probes were developed to evaluate their practical applications in bioimaging.The main research can be summarized as follows:1.In chapter 2,by introducing a rigid molecular structure and expanding the?-conjugated system of rhodamine,a novel near-infrared fluorescent dye HN7,with a molar extinction coefficient of 137300M^-1cm^-1,large stokes shift of 73 nm and high fluorescence quantum yield of up to 0.72 in ethanol has been developed.The excellent photophysical properties enable HN7 to have enhanced contrast and brightness compared to traditional Rhodamine and Cy5 dyes in bioimaging applications.The spatial resolution is significantly improved and the tissue imaging depth is also satisfactory.Moreover,utilizing the robust rhodamine-based spirolactam sensing platform,HN7 has beem applied to comstruct NIR probes.Herein,a novel near-infrared Hg²⁺fluorescence probe HN7-S,was designed and synthesized.HN7-S shows high sensitivity and selectivity for detection of Hg²⁺,and it has been successfully applied for the imaging of Hg²⁺in living cells,tissues and mice.The new dye HN7 proved to have great potential in bioimaging applications.2.Among the various fluorophores,the classic Xanthenes dyes including rhodamine and fluorescein have attracted remarkable interest on account of their excellent photophysical properties.Moreover,to take advantage of the long-wavelength region?>600 nm?,in recent years,many efforts have been made to develop new Xanthenes dye analogues.As well in our previous work,by introducing a practical strategy of constructing a rigid molecular structure,we have successfully developed a series novel functional fluorescent dyes HN1-7 with long-wavelength emissions and high fluorescence quantum yields.Besides HN7,it is found that the rigid dyes HN2,HN4,HN6 possess excellent two-photon properties excited by the near-infrared laser pulses with the two-photon microscope?TPM?.Thus,this is a good opportunity to develop TP probes with long-wavelength emissions for biological imaging applications.In another our work,utilizing a Hg²⁺induced nucleophilic cyclization reaction,we reported an ultra sensitive rhodamine based probe with a smart thiospirolactam recognition group.Now we found that the cyclization process could be accomplished by HOCl distinguishing many other ROS.Herein,in this chapter,combining the rigid TP dyes HN2 and the novel thiospirolactam recognition group,we present a rational-designed probe for monitoring HOCl level in living system.Owing to the specific HOCl induced cyclization reaction,the as-obtained long-wavelength TP probe rhodamine analogue HN2 thiospirolactam derivative?HN2-TP?exhibits excellent sensitivity and high selectivity over other common ROS and RNS even at higher concentrations.Moreover,the novel probe can be used as an indicator to monitor the level of HOCl in living cells and tissues,which shows the potential applications in biological imaging.