| Endocellular biothiols,normally including cysteine（Cys）,homocysteine（Hcy）and glutathione（GSH）,perform pivotal actions in various physiological activities such as protein synthesis,cellular metabolism,signal transduction and the regulation of oxidative stress.Present studies have found that the abnormal cellular levels of biothiols are closely related to numerous human diseases,such as Alzheimer’s,growth retardation,liver injury and cardiovascular disorders.Meanwhile,present studies have found that there is a tightly symbiotic relationship between Cys,Hcy and GSH in metabolic processes,and the concentration fluctuations of each biothiol would exert a significant effect on the others.Therefore,developing effective methods for simultaneous and selective determination of these biothiols in bio-systems is of great significance,which is beneficial for elucidating the complicated relationship between them and figuring out their cellular functions.Fluorescent chemosensors,integrated with laser confocal fluorescence microscopes,have been diffusely used for the visualization of biological species by virtue of high sensitivity and selectivity,real-time sensing,operational simplicity,relatively low cost,and so on.Among many fluorophores,coumarin derivatives have been widely used in recent years,due to their excellent optical properties,such as large stocks shift,high fluorescence quantum yield,good optical stability and structural flexibility.To selectively detect Cys,Hcy and GSH,two multi-sites organic molecule fluorescent chemsensors were designed and synthesized based on coumarin derivatives fluorophore,and the spectral properties and biological imaging capabilities in response to biothiols were investigated.The specific contents of this paper are as follows:Chapter 1.The design and research of fluorescence sensors based on different dye organic molecules,especially coumarin-based fluorescent chemsensors are briefly introduced.On the basis of the current research status of fluorescent sensors for single detection and discriminative detection of biotiols and the main difficulties at present,the research purpose and specific content of this paper are proposed.Chapter 2.A chlorinated coumarin based triple-excited fluorescent probe CC has been synthesized successfully,which achieves for discriminative and quantitative determination of Cys,Hcy and GSH through three different excitation and emission channels based on different reaction mechanism（Cys: Substitution-AdditionCyclization;Hcy: Substitution-Rearrangement-Addition-Cyclization;GSH:Substitution-Addition-Cyclization-Cleavage）.In addition,CC exhibits favorable sensing properties such as excellent selectivity and sensitivity,large fluorescence enhancement,low limits of detection,good water solubility and fast response speed.Fluorescence bioimaging in living cells proves that CC could be applied for discriminative visualization of endogenous and exogeneous Cys,Hcy and GSH using three distinct emission channels.Chapter 3.A coumarin-based bis-reaction-triggered highly specific Cys fluorescent probe CT-C has been constructed,including α,β-unsaturated ketone as Michael addition site,and 2-thiophenecarbonyl moiety as leaving group and quenching group,ensuring the occurrence of two successive cascade reaction stages.CT-C shows a twostage fluorescence response to Cys: first,sulfydryl of Cys attacks α,β-unsaturated ketone C=C bond,which induces rapid fluorescence enhancement;then,Cys continues to react with addition product to remove 2-thiophenecarbonyl moiety and induce slow fluorescence quenching.However,Hcy/GSH only attack the α,β-unsaturated ketone C=C bond of CT-C,which induces the slow and weak fluorescence enhancement.CTC exhibited satisfactory optical response properties,such as a fast response time,ultrahigh specificity and selectivity,and considerable fluorescence enhancement towards Cys.As expected,CT-C is also applied for biological imaging of Cys in living cells successfully. |
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