| Cyanine dyes as a kind of fluorescent dyes,have many advantages,such as large molar extinction coefficient,adjustable range of absorption and emission spectra,easy to synthesis and so on.They are widely used in biological fluorescence analysis and fluorescence imaging.Although cyanine dyes are widely used,there are shortcomings in photochemical stability,especially near-infrared cyanine dyes such as pentamethine(Cy5)and heptamethine cyanine(Cy7)which are poor in photostability.Therefore,it greatly limits its industrial application.In the second chapter,we designed and synthesized three kinds of meso-substituted pentamithine cyanine dyes,whose excited state were adjusted by introducing meso-phenyl groups and modifying the amino groups and hydroxyl groups in the phenyl group.It is expected that shortening the excited state life can improve the stability of cyanine dyes.The results show that the dyes with amino and hydroxyl electron donors have high photostability.Femtosecond transient absorption experiments show that the amino groups reduce the excited state lifetime of cyanine dyes,and the photostability is negatively correlated with the excited state.At the same time,it can be found that these cyanine dyes can well locate in the mitochondria of living cells.In third chapter,we synthesized three halogens-substituted pentamithine cyanine dyes: Cy-H,Cy-Cl and Cy-Br.The results show that the introduction of halogen can improve the molar extinction coefficient of the dye and the order of quantum yield is Cy-Br <Cy-Cl <Cy-H,indicating that the introduction of halogen reduces the fluorescence quantum yield of the dye.At the same time,the yield of singlet oxygen of Cy-Br was significantly higher than that of Cy-Cl and Cy-H.In addition,MTT test show that Cy-Br has good photosensitizer properties,low dark toxicity and high phototoxicity.Mechanism studies have shown that Cy-Br can well locate in mitochondria,produce singlet oxygen by light,induce apoptosis,and kill cancer cells. |
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