Synthesis Of Single-molecule/Dual-target AIE Fluorescent Probes And Application In Cell Imaging

Fluorescence imaging has become a powerful detection tool because of its noninvasive,high sensitivity,in situ and real-time visualization of biological species at the subcellular level.Many probes have been developed for imaging intracellular active substances and/or single/double organelles.However,due to π-π stacking and other non-radiative pathways,conventional fluorophore is susceptible to aggregation-caused quenching(ACQ),which may result in weak fluorescence emission and photobleaching under Aggregation.AIEgens have no fluorescence or weak fluorescence in solution,but due to Restriction of Intramolecular Motions(RIM),they emit strong fluorescence in the state of aggregation.AIEgens usually exhibit large Stokes shift,superior photostability and high sensitivity,and have good performance in monitoring esterase activity and other bioactive substances in living systems.Therefore,AIE fluorescent probes show great potential in biological imaging.Based on the advantages of AIE optical probe in cell imaging and other aspects,this paper designs and studies the imaging of three kinds of organic small molecule probe based on the single molecule/double target fluorescence probe reported in the existing literature.This paper is mainly divided into the following five chapters:In chapter 1,literature review mainly describes the basic characteristics and applications of molecular fluorescent probes,as well as the research status of AIE fluorescent probes and single molecule/double target AIE fluorescent probes in recent years.In chapter 2,a mitochondrial membrane potential recognition probe(CSP)was prepared.The probe CSP contains pyridine cation to target mitochondria through electrostatic interaction with the electronelectronic mitochondrial membrane.However,when the mitochondrial membrane potential decreases,CSP migrates from mitochondria to lysosome and is reversible.Therefore,CSP is a mitochondrialysosome migration probe.Linking diethylamine as electron donor group to form D-π-A structure is beneficial not only to enhance twisted intramolecular charge transfer(TICT)effect,but also to make the emission peak redshift.Solid fluorescence reaches the peak at 672 nm and the absolute quantum yield is 9.8%,indicating that CSP has the characteristics of low light damage and high image signal-to-noise ratio,which is suitable for biological imaging.In chapter 3,fluorescent probe of AIE(NAP-Py-E)that can migrate from mitochondria to lipid droplets(LDs)is prepared.The fluorescent probe can target mitochondria through the electrostatic interaction between pyridine cation and electronegative mitochondrial membrane.After being hydrolyzed by carboxylesterase in mitochondria,the hydrolyzed product migrates to LDs due to its high hydrophobicity.The solid fluorescence emission peak of the AIE fluorescent probe NAP-Py-E is located at 725 nm,reaching the near-infrared luminescence region,and the solid quantum yield is 3.12%,showing a typical AIE phenomenon.In preliminary cell experiments,the co-localization rate of NAP-Py-E and mitochondria was up to 0.85,and the co-localization rate of hydrolysate and LDs was up to 0.90.Since NAP-Py-E has better enzyme detection ability and higher AIE factor,we further investigated the performance of NAP-Py-E in cell viability assessment.In chapter 4,a fluorescent probe Mito-TTPE was prepared,which can be used for dual-organelle imaging,cell viability assessment and photodynamic ablation of cancer cells.The fluorescent probe contains a pyridine cationic part,which targets mitochondria by electrostatic interaction with the electronegative mitochondrial membrane.In addition,the fluorescent probe selects acetoxy group as the esterase activable site.After being hydrolyzed by mitochondrial esterase in living cells,part of it is converted into LD-TTP,which can be specifically accumulated in LDs.Live,apoptotic,and dead cells can be visually distinguished by monitoring different bicolor emission and dual-organelle targeting changes using Mito-TTPE.Therefore,MitoTTPE can be used to evaluate cell viability.In addition,the fluorescence probe MitoTTPE has a stronger D-π-A effect,and its ability to produce reactive oxygen species(ROS)is significantly higher than that of LD-TTP.Therefore,Mito-TTPE has a strong role in photodynamic ablation of cancer cells.In chapter 5,three kinds of single molecule/double target AIE probes are summarized and their future work is prospected.