Design And Synthesis Of Organic Fluorescent Probe For Detecting Cysteine

Biothiols such as cysteine?Cys?,homocysteine?Hcy?,and glutathione?GSH?play a key role in maintaining biological redox homeostasis,intracellular signal transduction,tissue growth,human metabolism,and other physiological and pathological processes.Therefoer,selective detection of such thiols is essential for understanding the function of biothiols.Cys is the most common biothiol in human plasma,and its normal concentration is 30-200?M in cells.High cysteine concentration will lead to neurotoxicity and too low concentration will be closely related to slow growth,bleaching of hair pigment,edema,drowsiness,liver injury and other symptoms.Therefore,the development of a novel probe that distinguishes cysteine?Cys?from glutathione?GSH?and hypercysteine?Hcy?is essential for a better understanding of the important role of biothiols in human physiology and pathology.On the basis of summarizing the previous work,we designed and synthesized two fluorescent probes which specifically recognized cysteine,and studied its photophysical properties,response mechanism and cell imaging.The details are as follows:1.A pyridazine annelated perylene based ratiometric fluorescent probe PAPC is synthesized for highly selective detection of Cys.PAPC exhibits strong blue emission in PBS,while the red emission at 605 nm can be observed in the presence of Cys.The probe PAPC shows ratiometric fluorescence(F₆₀₅/F₄₆₀)detection of Cys with wide linear range of 1-120?M and low detection limit of 0.19?M.Super large stokes shift?170 nm?and ratiometric fluorescence endow the probe low background signal.The discrimination of Cys over Hcy and GSH can be achieved through the difference of the ratiometric fluorescence.In addition,the probe has been proven to track Cys in real samples such as urine and HeLa cells.2.A novel off-on fluorescent probe TIA based on pyridazine annelated perylene is designed and synthesized,where the acryl group acts as a recognition site and electron acceptors to quench parental fluorescence.The conjugated addition/cyclization reaction of Cys with the acrylate group of the probe TIA introduces the detachment of the two acrylate groups,resulting the formation of the dye TIA-OH and a significant 70-fold increase of fluorescence at 540 nm with a rapid response time?less 5 min?.In addition,another acrylate group introduced on the mother fluorophore endows TIA-OH 10-fold higher fluorescence quantum yield than the parent dye.The high signal-noise-ratio endows TIA the high sensitivity and the low detection limit?0.11?M?and wide linear range?10-100?M?for Cys.What's more,the high cell membrane permeability and specificity for Cys of the probe ensure the application in fluorescence imaging of living cells to detect intracellular Cys.