A Benzoyxazine-based Ratiometric Fluorescent Probe For PH Imaging In Living Cells And Bacteria

The intracellular pH value is important to many physiological processes(such as cell metabolism,enzyme activity and immune function).The pH homeostasis of intracellular is key to ensure the normal growth of cells.Different organelles have different pH ranges,for example,the pH of lysosomes is relatively acidic,while the pH of mitochondria is relatively alkaline.Disturbance of pH usually leads to a variety of diseases and dysfunction of organelles.Therefore,real-time detection of intracellular pH value is essential to prevent the occurrence of diseases.Fluorescent probes possess various advantages such as easy operation,high sensitivity,and excellent cell compatibility.Besides,they have made outstanding contributions in the fields of analysis and cell imaging.In this paper,we designed and synthesized a ratiometric fluorescent probe for monitoring the change pH value of solutions based on the intramolecular charge transfer mechanism,which realized the detection of the hydrogen ion concentration in solutions.Meanwhile,this probe has been successfully applied to biological imaging on living cells and bacteria in different pH values.Chapter One.It mainly introduces the development of fluorescent probes and several common recognition mechanisms of probes,including photoinduced eletron transfer,fluorescence resonance energy transfer,excited state intramolecular proton transfer,aggregation-induced emission,and intramolecular charge transfer.Fluorescent probes have made good contributions in the fields of bioimaging,especially for monitoring changes in intracellular pH value.This chapter also focuses on some fluorescent probes which used for pH sensing in organelles and cells,including endsomes,lysosomes,mitochondria,and non-specific cells.Chapter two.It mainly introduces an intramolecular charge transfer ratiometric fluorescent probe,whcih used 2,3,3-trimethylindole compound and naphthalene formaldehyde as the main reactants to form a ?-? structure.The structure of the probe was characterized by mass spectroscopy,1H NMR,13C NMR and Fourier transform infrared spectroscopy.The reaction mechanism of the probe to the changed pH of the solution was explored through ultraviolet-visible spectroscopy and fluorescence spectroscopy.Apart from that,the reversibility,selectivity and biological toxicity of the probe were tested,and the results showed that the probe possesses excellent reversibility and selectivity,as well as good biocompatibility.Finally,the probe realized the biological imaging application of HeLa cells and E.coli cultured at different pH values.