The Synthesis And Characteristics Of �Light-up� Fluorescent Probes And Investigation Of Their Applications In Biological Imaging And Sensing

Fluorescence imaging technologies have been widely used in biomedical research due to their significant advantages in terms of simple operation,low cost,and high spatial resolution,which are beneficial to reveal the important physiological and pathological processes."Light-off"fluorescent probes are usually not suitable for bioimaging and sensing.In contrary,"light-up"fluorescent probes can be easily used for imaging or sensing with high signal-to-noise-ratio,and have found increasingly broad applications.In this thesis,several"light-up"fluorescent probes are designed and developed based on the following photophysical mechanisms,including restriction of intramolecular motions?RIM?,excited state intramolecular proton transfer?ESIPT?,and twisted intramolecular charge transfer?TICT?mechanisms.Based on the systematic investigation of their photophysical properties,the fluorescent probes developed in this thesis are used in the following aspects,including in situ detection of high-concentration calcium ions,specific imaging of lipid droplets,and detection of the bacterial membrane permeability.The main content is as follows:Firstly,the AIE probe SA-4CO₂Na was prepared by modifying of the AIE-active salicylaldazine skeleton with the sodium iminodiacetate moieties,which can be used for in situ light-up detection of high concentration of calcium ions?0.6�3.0 mM?.It can also be used for the diagnosis of hypercalcemia,selective staining of calcium deposits in meningioma slice,wash-free imaging of microcracks on bone surface and microdefects in hydroxyapatite scaffolds.Secondly,the specific fluorescence light-up imaging of lipid droplets is achieved by using the fluorescent probe DCQTB with TICT property.The probe is almost non-emissive in aqueous solution,but has strong fluorescence in a hydrophobic microenvironment.The probe has strong photostability,low phototoxicity,excellent biocompatibility and high two-photon absorption cross-section,which can be used for wash-free imaging and real-time motion monitoring of lipid droplets.Finally,the fluorescent probe HBT-Dextran was prepared by modifying of dextran with AIE-active 2-?2-hydroxyphenyl?benzothiazole fluorophore.It was found that the probe could be enriched in the bacteria with damaged bacterial membrane and light up the fluorescence,but cannot stain normal living bacteria.It thus can be used to detect the changes in bacterial membrane permeability.