Design,Synthesis And Properties Study Of Quinoline-based And Naphthalimide-based Two-photon Fluorescent Probes For Viscosity

Small molecular fluorescent probe has become the vital tool in cells imaging,due to its efficient localization in cells and quick detection of the micro-environmental signal substances and properties,such as signal small molecular,metal ions,viscosity and polarity.People can design and synthesis ideal small molecular fluorescent probe via simple synthesized methods,which can be used in imaging cell even sub-cellular organelles.Two-photon fluorescent probe has become the important tool in cells imaging for micro-environment over one-photon fluorescent probe,owing to the lower excitation energy,deeper penetration,smaller photon damage and decrease of auto-fluorescence.As the "digestive organs" in living cells,lysosome is responsible for dissolution and digestion during cells physiological process with a lot of lysozymes contained in the acid micro-environment(4.5～5.5).Dysfunctions of lysosome are related to cells physiological process and many diseases.Intracellular lysosomal viscosity plays a critical role during cellular diffusion-controlled processes,including the transportation and interaction of bio-molecules.Abnormal variations in intracellular lysosomal viscosity are related to many diseases and pathologies,such as Alzheimer’s disease and atherosclerosis.So it’s important to design a novel two-photon fluorescent probe for intracellular viscosity,even for intracellular lysosomal viscosity.On the basis of reading and investigating numbers of literatures,we developed two fluorescent probes,which were characterized by 1H NMR,13C NMR,and ESI mass spectrometry accurately,for viscosity detection.In addition,we further investigated the Vis-UV absorbance spectra,fluorescence emission spectra and two-photon absorbance cross section for their photo-properties.Moreover,we also obtained good results via confocal two-photon fluorescent biological imaging,fluorescent lifetime imaging and fluorescent vivo imaging in application in bio-imaging.First,we simply introduced structure of fluorescent probe with fluorescence emission mechanism,as well as the advantages of two-photon microscopy imaging technology.Second,we designed a novel quinoline-based two-photon fluorescent probe MCN via introducing a strong electron-withdrawing group dicyanidinyl to quinoline parent.MCN showed a great response to viscosity induced by water-glycerol and micro-environment.MCN possessed a perfect two-photon property due to the great D-π-A construction which was formed by electron-donating group methoxy group,conjugated system 6-substituted quinoline group,and electron-withdrawing group dicyanovinyl.Meanwhile,MCN was water-soluble,low cytotoxicity with stable fluorescence emission attributed to the quinoline parent.Moreover,it was confirmed that MCN could perform as an excellent two-photon viscosity fluorescent probe for detecting viscosity variations in HeLa cells qualitatively and detecting viscosity distribution in HeLa cells quantitatively according to the confocal two-photon fluorescence microscopy imaging and two-photon fluorescent lifetime imaging with good linear relationship between τ of MCN and solvent viscosity η.MCN is a potential candidate of two-photon fluorescent probe for monitoring micro-viscosity in vivo in zebrafish.Third,we developed a new naphthalimide-based two-photon fluorescent probe Lyso-NP for lysosomal viscosity variations detection.Lyso-NP was constituted with naphthalimide parent,lysosomal targeted group morpholine at "N" position,and 4-substituted N,N-dimethylamino phenylacetylene.Dimethylamino played the rotor role in the structure owing to its fine electron-donating capacity,thus Lyso-NP could serve as an excellent fluorescent probe for lysosomal viscosity.Lyso-NP possessed a perfect two-photon property due to the great D-π-A construction which was formed by electron-donating group N,N-dimethylamino,conjugated system 4-substituted naphthalimide group,and electron-withdrawing group morpholine.Meanwhile,Lyso-NP was water-soluble,low cytotoxicity with stable fluorescence emission attributed to the naphthalimide parent.Moreover,it was confirmed that Lyso-NP could perform as an excellent two-photon viscosity fluorescent probe for detecting viscosity variations in MCF-7 cells qualitatively and detecting viscosity distribution in MCF-7 cells quantitatively according to the confocal two-photon fluorescence microscopy imaging and two-photon fluorescent lifetime imaging with good linear relationship between τ of Lyso-NP and solvent viscosity η.