Synthesis And Biological Imaging Applications Of Fluorene And Triphenylamine Fluorescent Derivatives

Fluorescent technology is widely used in the detection of anions and macromolecules and bioimaging in vivo and in vitro with features of rapid response,high sensitivity,easy operation,excellent specificity,real-time imaging and low cost.However,the present fluorescent dyes suffer from short-wavelength absorption and emission,poor photostability,small Stokes shift,ACQ phenomenon and poor membrane permeability,which limit its practical application in biological recognition and imaging.In order to overcome the shortcomings stated above and expand the applications of fluorescent probes,fluorescent probes based on dimethylhydrazine and triphenylamine were designed and synthesized.Then we haved studied the mechanism of the fluorescence response and detection.Moreover,the probes were applied in the filed of biological imaging.Labeling nucleic acids,chromatin and nuclear in cell are of great significance for understanding gene expression,cancer therapy,and pathological processes.A novel cationic fluorophore FTI based on thiophene group modified dimethylhydrazine was synthesized and characterized by nuclear magnetic spectra,high resolution mass spectra,infrared spectra.The solvent experiment demonstrated the dependence of its photophysical properties on the environment and was confirmed by Gaussian calculation.The probe FTI showed visible light excitation?436 nm?,large Stokes shift?135 nm?and orange emission?571 nm?in PBS buffer solution.FTI displayed an obvious and sensitive fluorescent response to DNA in vitro with a6.4-fold quantum yield increasing and a detection limit of 596 ng/mL in vitro.The probe bound to DNA by inserting into base pairs of DNAs in vitro.With low cytotoxicity,good photostability and nuclear membrane permeability,FIT could stain nucleolus in HepG-2 cells due to its special affinity to RNA in live cells.In view of the wide application and severe toxicity of cyanide,a D-A-D type triphenylamine-benzothiadiazole fluorescent probe TCNT was designed and synthesized.Then the molecular structure of TCNT was characterized by FTIR,nuclear magnetic resonance spectroscopy and mass spectrometry.TCNT possessed properties of AIE and TICT,exhibiting orange-red fluorescence emission??_F=0.124,596 nm?and a large Stokes shift?135 nm?in almost pure water systems.TCNT showed high specific and sensitivity(detection limit equals to 0.35?mol·L^-1)to CN^-with a 2.53-fold enhancement of quantum yield in aqueous solutions.The Job's plot proved that the stoichiometric ratio between CN^-and TCNT is 1:1.The recognition mechanism of TCNT sensing cyanide was ascribed to nucleophilic attack of CN^-toward vinyl group based on the observation of ¹H NMR titration.According to results of calculation by density functional theory,it was ascribed to affecting the efficiency of the ICT process in molecule,resulting in red-shift absorption and enhanced fluorescence.In addition,TCNT could be made into fluorescent strip which was utilized to detect CN^-in aqueous solution.With low toxicity and good cell membrane permeability,TCNT was applied for monitoring the levels of CN^-in HepG-2 cells and achieving bioimaging in live organisms.