Sulfur Containing Functionalized Fluorescent Probes: Design,Synthesis And Bioimaging Applications

Small molecule fluorescent probe technology has developed rapidly due to its advantages of simple operation,low cost,high sensitivity and selectivity,rapid response,and high adaptability to biological and environmental samples,especially in the detection of key biomolecules.Received widespread attention.Among them,the nonlinear dependence on light intensity enables highly localized excitation to improve spatial resolution,and multiphoton fluorescence microscopy has become a powerful technique for three-dimensional imaging in biological systems.On the other hand,near-infrared light can penetrate many biological tissues,so using excitation light of near-infrared wavelength for excitation can reduce light damage to the sample and help imaging biological samples.In recent years,fluorescent probes based on oxygen group elements（sulfur,selenium and tellurium）compounds have become an important means for detecting reactive oxygen species（ROS）,reactive nitrogen（RNS）and biological thiols,and many have been developed with single or A novel heterocyclic fluorescent dye with multiple oxygen,sulfur,selenium or tellurium sites.Based on this,this paper uses sulfur as the key atom for research.The following two aspects are the main research work of this paper:1.Hemicyanine dyes including hemiindocyanine and hemibenzoindocyanine have attracted considerable attention to develop near-infrared probes for in vivo fluorescence imaging.However,semibenzothiazolyl cyanine dyes（MTR）are rarely used to detect analytes.In this work,in order to expand the sensing applications of MTR,we proposed a simple dye preparation method.A fluorescent probe MTR-HH for detecting H2O2 based on semibenzothiazolyl cyanine was designed and synthesized.By combining the self-immolation mechanism with the H2O2 selective aryl borate group,the fluorescence of the proposed NIR probe on H2O2 was enhanced by 284 times,and the detection limit was 0.32 μM.In addition,the detection probe can also show the selective effects of other common metal ions and anions and cations on H2O2,indicating that the new probe is suitable for sensing H2O2 in actual samples.MTR-HH has been successfully applied to monitor exogenous and endogenous H2O2 in vivo,indicating its great potential in NIR bioimaging.2.Nucleophilic groups with spatial proximity effects may have excellent tunability of conjugation systems,which provides an opportunity to construct proportional probes with large emission displacements.In this article,we designed a coumarin-based probe（Cou-PP）,which was partially conjugated with mercaptopropyl-modified benzoindole to limit its electron withdrawing ability and accompanied by short wavelength emission.Due to the controllable regulation of the intramolecular charge transfer（ICT）efficiency of the coumarin molecule,once the nucleophilic sulfur atom is combined with Hg2+/Me Hg+ to recover the alkylated electron-deficient imine group,a new large-scale π-conjugation push The pull structure can have significant red shift emission,which is conducive to highly sensitive and accurate detection.The probe has been successfully used to sense Hg2+/Me Hg+ in actual water samples,and visualize mercury species in living cells,with satisfactory results.