Synthesis And Application Of Mitochondrial-target Fluorescent Probes

Mitochondria,as essential and interesting organelles within the eukaryotic cells,play key roles in a variety of physiological processes.As their principal function is the energy production,mitochondria are known as the cellular power house.Mitochondria require the appropriate microenvironment and specific quantities of biomolecules to perform their cellular functions,while breakdown of the homeostasis of biomolecules or micro-environmental mutations leads to mitochondria malfunctions,and their abnormalities are closely associated with Alzheimer’s disease（AD）and other diseases.Therefore,it is important to detect microenvironment and biomolecules changes in mitochondria.In this paper,three fluorescent probes for the detection of mitochondrial SO₂ and viscosity,HClO and H₂O₂ were successfully designed and synthesized in combination with the research status of mitochondria-targeted fluorescent probes,and their optical properties and bioimaging applications were investigated.（1）A novel mitochondria-targeted double-detected fluorescent probe Mito-VBe for multiple imaging of mitochondrial viscosity and SO₂ was designed and synthesized using a benzothiazole fluorescence platform.Probe Mito-VBe has high selectivity and ratiometric fluorescence response to SO₂/HSO₃^-by the mechanism of nucleophilic addition.In addition,the color change before and after the probe response is obvious,and can be observed by naked eye.The probe has potential applications to explore the relationship between mitochondrial SO₂ and viscosity.（2）A new ratiometric fluorescent probe（CMS）was rationally designed and synthesized based on fluorescence resonance energy transfer（FRET）mechanism for detecting HClO.Probe CMS has a large Stokes shift of 150 nm that can greatly reduce the selfabsorption of the fluorescence and shows highly selective toward HClO among various relevant analytes.In addition,the response time of CMS to HClO is less than 12 s which shows a good time resolution of CMS.The detection limit of CMS toward HClO is calculated to be 0.2657μM.Furthermore,the co-staining experiments demonstrate that CMS has a perfect mitochondria targetable ability and it can be successfully applied to image HClO in mitochondrial of living HeLa cells.（3）A novel mitochondria-targeted fluorescent probe for H₂O₂ has constructed based on acoumarin as the fluorescence platform.The probe displayed highly sensitive,selective and quantitative for detection of H₂O₂.In addition,a new fluorescent probe has been rationally designed for specific detection of cysteine.The probe utilizes an acrylate moiety as thiol recognition site.Upon the treatment with Cys（Cysteine）,the probe shows a distinct ratiometric fluorescent response and the detection limit obtained from fluorescent titration is 0.1256μM.The probe shows high selectivity and sensitivity for Cys over other amino acids and GSH.What’s more,the probe has low cytotoxicity and can be successfully located in lysosome to bioimage Cys in living cells.Therefore,the probe might have application in the investigation of Cys roles in biological systems.In this paper,three fluorescent probes were synthesized using quaternary ammonium salt as mitochondrial targeting group,and the molecules were characterized by ¹H NMR,¹³C NMR,HRMS and IR.The UV and fluorescence optical properties of three probes were studied.In addition,cytotoxicity and mitochondrial localization studies were performed on probe Mito-VBe and CMS,the results showed that the two probes were less cytotoxic and could be successfully localized in mitochondria.The successful determination of intracellular mitochondrial HSO₃and HClO by probe Mito-VBe and CMS,respectively,indicates that the probes have potential biomedical applications.