Synthesis And Application Of Fluorescent Probes Based On Novel Xanthene Dyes

Small-molecule probes based on fluorescent signal transduction afford an outstanding approach to detecting target ions with rapid responsive time,high sensitivity,simple operation and easy visualization.Particularly,the structures of the small molecule probes are convenient to be modified for specifically targeting subcellular organelles such as lysosome,mitochondria,cell nucleus and cell membrane.Fluorescent probes are widely used in biological detection.To overcome the obstacles of some probes in biological imagings,in this thesis,we have carried out the following works:1.We have designed a novel xanthene dye R4.The dye R4 inherits a facile derivatizable spirolactone structure from rhodamine dyes.We have prepared probes R-Hg and R-Cu by introducing specific analyte-responsive groups on the spirolactone structure.Spectral investigations suggested that the probe R-Hg can be functioned as a highly Hg²⁺-selective fluorescent probe with a highly sensitive response?0.65 nM?.R-Cu demonstrates a unique ability to discriminate between Cu²⁺and chemically close ions with a low detection limit.Furthermore,probes R-Hg and R-Cu are lysosome-targetable,and is suitable for biological application.2.According to the effect of the electron-withdrawing groups within R4,we have used acetyl group to replace the cyano group and synthesized the dye H2.The dye H2 is extremely pH sensitive,and can be applied to detection of p H value in living cells.3.We have designed a novel carbazole-rhodamine hybrid dye X2 by combining the structures of carbazole and rhodamine.The dye X2 shows the following advantages as a fluorescent dye:?1?it showed reasonable water solubility because it has a ring-opened zwitterion structure in aqueous phase,which is favorable for cell membrane permeability;?2?it has higher fluorescence quantum yields;?3?X2 showed stronger tolerance to p H than rhodamine.Based on X2,the probe X3,a highly Cu²⁺-selective fluorescent probe with a highly sensitive response,have been prepared.Meanwhile,the probe X3 is cell membrane permeable and can be utilized for Cu²⁺detections in living cells.In conclusion,three novel fluorescent dye R4,H2 and X2 have designed and synthesized.They are photostable,cell membrane permeable,and biocompatible.Based on these dyes,a few fluorescent probes have been prepared.