Design,Synthesis And Biological Application Of Novel NIR Lipid Droplet Probes

As the basic unit of life,cells have complex and fine substructures,such as nucleus,mitochondria,lysosome,endoplasmic reticulum,lipid droplets,dictyosome and so on.Lipid droplet,as an important organelle,plays an important role in lipid storage,transport,protein degradation,membrane transport and signal transmission,and is closely related to the occurrence and development of diseases such as fatty liver,cardiovascular disease and diabetes.When the function of lipid droplets inside cells is abnormal,fat metabolism disorders will occur,resulting in obesity and even cancer.In order to understand the mechanism of lipid droplets influence on disease development,we have developed fluorescence analysis methods for in situ real-time.This thesis mainly carried out the following two parts:In the first part,a series of near-infrared fluorescence probes,LD-1-LD-4,were designed and synthesized,for real-time and in situ detecting lipid droplets changes in living cells.LD-1was selected as an excellent fluorescence probe of lipid droplets.In the low viscosity and high polarity environment,due to the intramolecular rotation of the probe,the excited state energy of the probe is released by non-radiative transition,resulting in weak fluorescence.In lipid droplets,the intramolecular rotation of the probe is blocked because of the high viscosity and low polarity environment,the release of non-radiative energy is reduced,and the fluorescence of the probe is significantly enhanced.Experimental results in simulated physiological system showed that LD-1 had a good linear response to different viscosity and was not interfered by p H changes and common active species in cells.Cell imaging experiments show that LD-1 has low cytotoxicity,good photostability,and can target lipid droplets efficiently and accurately.The probe has been successfully used for real-time imaging of lipid droplet changes during oleic acid stimulation,drug induction and iron death,and to distinguish cancer cells from normal cells.In the second part,in order to further develop lipid droplets specific targeting probes,we modified the lipophile properties of LD-2,and synthesized three new lipid-droplet targeting probes LD-2-C2,LD-2-C3 and LD-2-C6 by introducing aliphatic chain of different lengths.The experimental results show that the probe LD-2-C2 has a higher signal-to-noise ratio(SNR)in response to viscosity,and has a better lipid droplet targeting effect compared with the commercial lipid droplet targeting dye.Using this probe,the changes of lipid droplet morphology were observed in real time under the stimulation of oleic acid and drugs.The probe will provide a reliable tool for further studying the dynamic changes of lipid droplets and the pathogenesis of related diseases.