Design And Synthesis Of Novel Fluorescent Probes And Its Applications In Biological Imaging

Fluorescent probes have been evaluated as powerful tools to detect chemical agents in recent years,due to their high sensitivity,high selectivity,easy operation and fast response,and were used not only in conventional experiments but also in vivo studies.Especially for the living biological imaging research,the probes are advantageous because they cause less cell damage while displaying high spatial and time resolution capabilities in visualizing analytes.Hence,the design and synthesis of novel fluorescent probes,which can recognize these anions and cations,is desirable and significant.Here,we have designed and synthesized three fluorescent probes to detect Cu²⁺,Hg²⁺,Cd²⁺ and ClO^-.The mainly results were briefly summarized as following:（1）A new rhodamine derivative（RhS）with a recognition capability for Cu²⁺ was synthesized and employed as a reversible fluorescent probe for Cu²⁺ in drinking water and living cells.The spirolactam ring-opening of probe RhS induced by Cu²⁺ lead to a highly selective fluorescence "turn-on" response toward Cu²⁺ over other metal ions with micromolar sensitivity.The 1:1 stoichiometric structure between RhS and Cu²⁺ were supported by Job’s plot,MS and DFT theoretical calculations.The analytical results obtained by UV-Vis and fluorescence spectrophotometry show that the linear range and the limit of detection（LOD）of the present probe for Cu²⁺ are 0.50-20.00 and 0.11 μmol L-1,respectively.The present probe was applied to the detection of Cu²⁺ in drinking water with the recoveries ranging from 100.4 to 101.2%,and the fluorescence imaging for living He La cells.（2）A new rhodamine derivative（DRh）was synthesized as a ratiometric fluorescent probe for detecting Hg²⁺ in water and living cells samples.The recognition properties of the probe DRh with metal ions had been investigated in H2O/CH3CN（9:1,v/v;Tris-HCl 50 mmol L-1;pH = 7.0）solution by the UV-Vis spectrophotometry and the fluorescence spectrophotometry.The results showed that the probe DRh exhibited the selective recognition of Hg²⁺.Upon the addition of Hg²⁺,the spirolactam ring of probe DRh was opened.The 1:1 stoichiometric structure between DRh and Hg²⁺ were supported by Job’s plot,MS and DFT theoretical calculations.The linearly fluorescence intensity ratio（I582/I538）is proportional to the concentration of Hg²⁺ in the range 0-30 μmol L-1.The limit of detection（LOD）of Hg²⁺ is 0.008 μmol L-1（base on S/N=3）.The present probe was applied to the determination of Hg²⁺ in neutral water samples and gave recoveries ranging from 104.5 to 107.9%.Furthermore,the fluorescent probe also can be applied as a bioimaging reagent for Hg²⁺ detection in HeLa cells.（3）A water-soluble fluorescence probe（TF）derived from fluorescein has been developed.This probe can be used to detect ClO^-and Cd²⁺ under physiological condition based on oxidation and coordination reactions,exhibiting almost 64-fold and 4-fold fluorescence enhancement.The fluorescence of the probe can be enhanced by ClO^-and the LOD of ClO^-was 0.068 μmol L-1.The fluorescence of the probe can be enhanced Cd²⁺ and the LOD of Cd²⁺ was 2.2 μmol L-1.The experimentally observed changes in the structure and electronic properties of the probe in the presence of ClO^-and Cd²⁺ were modeled by density functional theory（DFT）and time-dependent density functional theory（TDDFT）computational calculations.Moreover,the present probe was successfully applied to the fluorescence imaging of ClO^-and Cd²⁺ in living cells.