The Design,Synthesis And Application Of Lysosome-targeting Fluorescent Probes

In past decades,fluorescent probe technology has been widely used in scientific research,especially in biological detection,environmental analysis and clinical detection.Small molecules play extremely important roles in biological systems,and accurate detection of these molecules is of great significance in both scientific research and clinical applications.Lysosomes are important organelles where these small molecules take part in physiological process.And a lack or excess of these species in lysosomes may lead to cell disfuction.So accurate detection of these small molecular species in lysosomes is meaningful.Fluorescent molecular probes have important applications in biological detection of these species due to their high sensitivity,fast detection speed,good repeatability and ease of use.Therefore,in this paper,we designed and synthesized two lysosome-targeting fluorescent probes to detect hypochlorous acid and lysosomal pH value.The main research contents are:(1)We introduced a new strategy of converting aggregation-induced emission(AIE)to fluorescence emission in solution into the rational design of new fluorescent probes.Two fluorescent probes based on this strategy,i.e.PDAM-Lyso and PDAM-Me,have been synthesized and tested in vitro and in vivo.The fluorophores of the two probes are both phenothiazine molecules which link to the diaminomaleonitrile(DAMN)moiety through imine bonds.The only di:fference between the two probes is that PDAM-Lyso is lysosome-targeting and PDAM-Me is not.In aqueous solution,the aggregation state of the probes depress their coordinative ability to metal ions,and the probes emit red fluorescence caused by AIE effect;However,when the imine bonds in molecules are selectively cut off by HClO,the DAMN moiety removes and the blue fluorescence of the reaction product appears.In this way,the selectivity of the DAMN-based probes has been successfully improved to HCIO against metal ions and other reactive oxygen species.The imaging of endogenous and exogenous HClO in cells with the two probes reveals that lysosome-targeting probes are of more advantages in the detection of natively generated HClO.Furthermore,the imaging of endogenous HClO in zebra fish suggests that PDAM-Lyso is capable to monitor the generation of HClO in vivo,illustrating that the strategy is of great significance in designing new probes.(2)Fluorescence imaging with tumor-specific fluorescent probe has emerged as a tool to aid surgeons in the identification and removal of tumor tissue.We report here a new lysosome-targeting fluorescent probe(NBOH)to distinguish tumor tissue out of normal tissue based on different pH environment in these cells.The probe exhibited remarkable pH-dependent fluorescence behavior in a wide pH range from 3.0 to 11.0,especially a sensitive pH-dependent fluorescence change at pH range between 3.5 and 5.5,corresponding well to the acidic microenvironment of tumor cells,in aqueous solution.Toxicity test and fluorescence cell imaging together with a sub-cellular localization study have been carried out revealing its low biotoxicity and good cell membrane permeability.And NBOH is successfully applied to the imaging of tumor tissue in tumor-bearing mice suggesting its potential application to surgery.