Construction And Performance Study Of Functionalized Quinone Cyanine Framework Fluorescent Probe

Due to their excellent photophysical properties,such as high molar extinction coefficient,long emission wavelength and good biocompatibility,cyanine dyes have received extensive attention.However,the conventional cyanine dyes have poor photostability,low solubility,and narrow Stokes shifts(< 30 nm),which can generally result in photo-damage and self-quenching due to back scattering from biological samples.Therefore,exploring new design strategies to develop long-wavelength(> 650nm)cyanine dyes with excellent photophysical properties and large Stokes shifts is of great importance for their bioimaging applications.In this thesis,focusing on the above shortcomings,a series of fluorescent dyes with long-wavelength emission(greater than650 nm)and large Stokes shift(greater than 30 nm)were obtained by modifying the cyanine skeleton.Meanwhile,the organelle(lysosome or mitochondria)targeted labeling is realized without the introduction of additional targeted groups.The main work contents are as follows:(1)By introducing a phenolic hydroxyl group on the polymethine chain and adjusting the terminal nitrogen heterocycle,it is a strategy to improve the photostability while changing the intramolecular charge transfer(ICT)properties of the cyanine.New quinone cyanine dyes Qcy-d T1,Qcy-d Q,Qcy-d T2 and Qcy-d I with large Stokes shift and long fluorescence emission wavelength were synthesized by Knoevenagel reaction.The maximum emission wavelengths of the four dyes are located at 688 nm,678 nm,731 nm and 725 nm,respectively,in the near-infrared region.And its Stokes shift is greater than 140 nm,which can effectively reduce background interference.Through the study of its imaging properties,the three dyes Qcy-d T1,Qcy-d Q and Qcy-d T2 have low cytotoxicity,good cell membrane permeability,and can achieve mitochondrial and lysosome targeting.(2)Using the dyes Qcy-d T1 and Qcy-d Q have the characteristics of positively charged and nearly planar aromatic ring system,the interaction of Qcy-d T1 and Qcyd Q with ct-DNA was systematically studied.The two dyes have the characteristics of high selectivity,high sensitivity(LOD = 4.06 n M,6.09 n M)and rapid detection for ctDNA.Through thermal denaturation,viscosity and phosphate experimental system,the interaction mechanism of dyes with ct DNA is discussed as electrostatic and intercalation combination.Both dyes can achieve specific detection of DNA in mitochondria.(3)The structures of dyes Qcy-d T2 and Qcy-d I contain phenolic hydroxyl groups and can form spiropyran structures by themselves.Therefore,using structural interconversion to change the fluorescent signal,the application of two dyes as p H fluorescent probes was systematically studied.The systematic studies of ultraviolet and fluorescence spectroscopy show that the two dyes are sensitive to p H,and other related substances do not affect the detection of p H and have good reversibility.The probe Qcy-d T2 has been applied to the visualization of lysosomal p H changes in living cells.The probe Qcy-d I can detect the p H in the aqueous solution ratiometrically,and successfully prepared a p H test paper and accurately measured the p H value.