Design,Synthesis And Performance Study Of Near-Infrared Xanthene-Cyanine Hybrid Dyes

Fluorescence analysis is widely used in field of biology and medicine as an intuitive and in-situ visual observation technique.It has many advantages such as high sensitivity,good selectivity and simple operation,and fluorescence analysis also has advantages of less damage to biological samples and good reproducibility,which other detection methods don’t have.As a practical tool of fluorescence analysis,organic small molecule fluorescent dyes are widely used in fluorescence analysis and imaging detection.However,the emission wavelength of traditional organic small molecule fluorescent dyes is too short,their Stokes shift is too small,and they can be easily light bleached,which results in low dorsal ratio and severe fluorescence self-quenching in the application of biological imaging,and all defects above limit their further application in vivo.Because of its long emission wavelength,near-infrared dyes show strong tissue penetration ability,low background fluorescence and phototoxicity,so the development of near-infrared dyes for in vivo imaging has become a major development direction of organic small molecule fluorescent dyes.In recent years,several research groups have improved traditional organic small molecule dyes and reported a variety of new near-infrared dyes.Among them,xanthene-cyanine hybrid dyes(such as CS dyes)are the best.Compared with traditional cyanine dyes,CS dyes have better light and chemical stability,and the fluorescent properties can be adjusted.However,CS dyes still have shortcomings such as absorption and emission wavelengths near the edge of the near-infrared region(maximum emission wavelength is generally<750 nm),and small Stokes shift,which limits their application in the field of biological imaging.In response to the above problems,this thesis uses molecular design and structural reconstruction to control the structure and performance of the xanthene-cyanine hybrid dye,and developed a series of new near-infrared xanthene-cyanine hybrid dyes with excellent performance.The specific research contents are as follows:(1)In order to overcome the problem that the emission wavelengths of CS dyes are closed to visible light area and still have background fluorescence interference,in the second chapter,we extend the dyes’absorption-emission wavelength through replacing electron acceptor,increasing the ring stiffness,broadening the conjugated system and other methods,ultimately we synthesized a series of xanthene dyes whose emission wavelengths are at 800nm or more,they can greatly reduce the background fluorescence interference in visible light.This series of dyes not only prolong the wavelength of CS dyes,but also inherit the advantages of CS dyes such as strong stability and adjustable sites,which makes this series of dyes have great application potential in the field of in vivo imaging.(2)In order to overcome the shortcomings of small Stokes shifts of CS dyes,in the second chapter,we increased the intracellular charge transfer effect(ICT)of the dyes by changing the electron acceptor in the dye,which made the dye successfully break through the Cyanine Limit and significantly increased the Stokes shift.In PBS buffer solution,the Stokes shift of the dye could reach more than 100 nm,which could effectively reduce its self-absorption and improve its signal to noise ratio.What’s more,this series of dyes have excellent optical and chemical stability,so the series of dyes have great potential in the field of medical imaging.(3)Abnormal viscosity of the microenvironment in the cell is one of the early symptoms of many major diseases.Monitoring changes in the viscosity of the cell is of great significance for the study of the occurrence and development of the disease and early diagnosis.In Chapter4,we introduced a new near-infrared dye CSP-VIS sensitive to viscosity by introducing a cyanide group to the bridged double bond in the xanthene-cyanine hybrid dye.The results show that CSP-VIS basically has no fluorescence in the near-infrared region in a low-viscosity environment,and as the viscosity increases,the fluorescence intensity of the probe CSP-VIS around 725 nm increases significantly,about 13 times,and the probe CSP-VIS The fluorescence intensity and viscosity show a good linear relationship(R~2=0.98678),which can quantitatively detect the viscosity in the microenvironment.In addition,CSP-VIS can respond specifically to viscosity without being affected by other cell microenvironment parameters(such as polarity)and other biomolecules,so it has good biomedical application potential.