AIE-active Fluorescent Probes For Ion Detection In The Environment And Its Application In Biological Imaging

The aggregation-induced luminescence(AIE)phenomena has been first proposed by Prof.Tang in 2001.Different from the traditional organic,inorganic and hybrid fluorescent materials,the fluorescence intensity of molecules and materials with AIE feature will obviously enhanced in solid and aggregate state.This unique feature endows the AIE-active materials for elegant overcoming aggregate-caused quenching(ACQ)effect of trational fluorescent materials and therefore should be of great promising for fabrication of fluorescent materials with better optical properties.In recent years,AIE-active materials have attracted great research interest and have been extensively explored for applications in different fields ranging from biological imaging,chemo-biosensor and photoelectric divices.To overcoming the disadanvates,such as ACQ effect and poor dispersibility in biological systems of trantional fluorescent materials,we designed and synthesized several AIE-active fluorescent probes with high water dispersibility and investigate their capability for detection of ClO-and Hg2+ in aqueous solution and living cells.The main content of this thesis can be divided into the following three parts.In the second Chapter,based on the typical AIE molecule tetraphenylethylene(TPE),we designed and synthesized an ionic fluorescent probe with AIE feature and well water dispersibility.The fluorescent probe can be used for the determination of hypochlorite in aqueous solution and living cells.The detection system has the characteristics of rapidity,selectivity and sensitivity.The response time is less than 1 minute,and many other anionic molecules will not affect hypochlorite detection.According to the results of UV-Vis spectrum,fluorescence spectrum,NMR and mass spectrum,we speculated that the detection system might be the reaction of hypochlorite and probe TPY to form TPE-CHO,resulting in the blue-shift of fluorescence.The results of cell activity showed that the probe possessed low toxicity and good biocompatibility.This study provides a fast,reliable and good method for the selective determination of hypochlorite.In the third Chapter,we reported a novel fluorescent sensor system based on the functional nuclear acids and mussel-inspired chemistry for detection of Hg2+.First,the polydopamine(PDA)was coated on the surface of cellulose nanocrystals to form PDA-co-CNC via self-polymerization of dopamine under alkaline conditions.On the other hand,the PDA-co-CNC displayed fluorescence quenching ability and stronger adsorption ability to ssDNA than dsDNA.Therefore,the combination of PDA-co-CNC and fluorescent dye labeled ssDNA can be used for selective and sensitive detection of Hg2+.When Hg2+was added into the sensing system,the ssDNA will form dsDNA owing to the formation of T-Hg2+-T hairpin.Therefore,the fluorescence will restore and the concentrations of Hg2+could be determined based on the changes of fluorescence intensity.The sensing strategy possesses the advantages,including high sensitivity,fast response,easy operation and mild experimental environment.Therefore,PDA-co-CNC nanomaterials combined with DNA show excellent application prospects in biological detection.In the fourth Chapter,we reported a lable-free fluorescent sensor system based on the functional nuclear acids to selectively detect Hg2+.First,the ionic AIE-active molecule TPY was adsorbed on ssDNA through electrostatic interaction to obtain fluorescent ssDNA-TPY complexes.Then,ssDNA-TPY complexes were adsorbed on PDA-co-CNC to quench the fluorescence.After adding Hg2+,ssDNA-TPY complexes will form T-Hg2+-T hairpin structure,which is similar to the structure of dsDNA.It is therefore the fluorescence of the system will restore.The changes of fluorescence sensor system could be utilized to determine the concentrations of Hg2+.As compared with previous sensor systems based on functional nuclear acids,fluorescent ssDNA is not required.