Near-Infrared Organic Fluorescent Dyes Based On Hemicyanine Derivatives: Design,Synthesis And Application In Bioimaging

In recent years,with the development of modern biology and technology,optical imaging based on fluorescent probes has been widely used in many fields,such as tumors diagnosis,biomolecules detection,and intramolecular environment monitoring.Therefore,the development of fluorescent or phosphorescent materials with different properties and functions has become an essential research topic in bioimaging.The near-infrared(NIR)fluorescent dyes have many advantages in fluorescence bioimaging due to their wide range of absorption and emission in NIR region,so they exhibit remarkable properties,such as deep tissue penetration,minimum photodamage to biological samples and minimum interference from background autofluorescence by biomolecules in the living system.However,low chemical and photo stability and weak water solubility limited their wide application.So,in our work,we designed and synthesized a series of novel NIR fluorescence dyes with high photostability,high fluorescence quantum yield and low cytotoxicity.Firstly,two organic NIR fluorescent dyes based on the hemicyanine structure were designed and synthesized.The benzothiazole and the benzimidazole groups were introduced into the classical hemicyanine structure,and the benzothiazole hemicyanine dye(Hc-BTZ)and benzimidazole hemicyanine dye(Hc-BIZ)were obtained,respectively.The results showed that both of these two dyes were responsive to the pH value,and Hc-BTZ was more sensitive than Hc-BIZ.The photostability of the Hc-BIZ was better than Hc-BTZ,and the fluorescence quantum yields of two dyes were higher than the commercial ICG dye IR-125.Secondly,we designed and synthesized the hemicyanine boron complexes Hc-BTZ-BF2 and Hc-BIZ-BF2,Hc-BTZ and HC-BIZ contained the O^N ligand,which can react with boron trifluoride ether.Both of these two complexes were responsive to the pH value and Hc-BTZ-BF2 is more sensitive to the pH value than Hc-BIZ-BF2.The photostability of two dyes is quite different.And the photostability of Hc-BIZ-BF2 is better than that of Hc-BTZ-BF2.After the coordination with boron trifluoride,the fluorescence quantum yields of two dyes decreased,but they were still higher than the commercial ICG dye IR-125.In addition,four kinds of NIR fluorescent dyes were used in confocal laser scanning fluorescent microsopy imaging.The results showed that these four dyes were suitable for cell imiging and strong NIR fluorescence could be collected in the cytoplasm of Hela cells.The strong NIR fluorescent signal,high cell uptake rate and low cytotoxicity to living cells made them widely used in fluorescence imaging.