Design,Synthesis And Bioimaging Of Novel Cysteine Fluorescent Probes

Scientists have found that the content of small molecule thiol cysteine（Cysteine,Cys）in patients can characterize the production and development of some diseases,and can even be cured by controlling the content of Cys in patients disease.Therefore,the quantitative detection of Cys in human body attracts extensive attention of researchers.Among many methods to detect Cys,optical detection method is favored by scientists because of its advantages of high sensitivity,strong specificity and so on.In this paper,two novel probes were synthesized by optical detection method to realize the specific detection of Cys.The orange-red fluorescence group CO（7-hydroxycoumarin-4-carboxylate ethyl）and the red fluorescence group LA10-（diethylamino）-3-hydroxy-5,6-dihydroben-zimium)xanthel-12-onium were synthesized and linked with acrylate as recognition groups.A fluorescent probe COAC（7-ethyl ester（butane-1,3-diethylt-riamine-2-acyloxy）with excellent properties was synthesized based on the protection/ deprotection strategy of hydroxyl groups 2-oxy-2h-benzopyran-4-carboxylate）and LAAC（3-（acryloxy）-10-（diethylamino）-5,6-dihydrobenzoy-12-sulfonium）.The basic properties of fluorophores were determined,and its p Ka,solvent and quantum yield were determined,and it was found that the fluorophore had good luminescence property and stability,which provided a good prerequisite for the fluorescence detection of probes.Subsequently,in order to test the basic properties of the probes,fluorescence titration experiments,reaction time experiments,p H effect experiments and selective competition experiments were carried out.The fluorescence intensity of the two probes was significantly enhanced when they reacted with Cys,indicating that the probes had high sensitivity and strong response.The p H test results showed that the two probes still had good detection ability under the changeable p H environment in the organism.In the selective competition experiment,it was found that other amino acids and biological thiols in the organism did not interfere with the detection of the probe,indicating that the probe has the advantage of specifically detecting Cys.The bioimaging capabilities of the probes were determined,and experiments such as cytotoxicity,cell time,and cell concentration were performed.The experimental results showed that in the cytotoxicity study of probe COAC,the average cell activity reached 85%,and the residence time of probe in cells was 30 min.Compared with COAC,probe LAAC had better biological detection properties.Excessive homocysteine（Homocysteine,Hcy）and glutathione（Glutathione,GSH）did not interfere with the detection of Cys by the two probes.This indicates that both probes have good selectivity both in vitro and in vivo.It was found that the probe LAAC had two-photon properties through two-photon cross section experiments.In confocal experiments,it was found that LAAC is a visual sensor that can quantitatively detect Cys in the nucleolus and lysosome,which is of great significance for the tracking and localization of the nucleolus in the future.