Ratiometric Fluorescent Probe Of Cathepsin B Based On ESIPT Imaging Of Cancer Cells

It has been reported that over expression of cathepsin B in a variety of malignant tumors,is considered to be the tumorigenesis and metastasis potential biomarkers,so accurate detection of the location and activity in cancer early diagnosis and prediction of metastasis plays an important role.Ratiometric fluorescent probe has two or more emission bands,so it can be realized by different emission bands in the fluorescence intensity ratio before and after the change detection.The detection results of self calibration can improve the accuracy of detection results.Therefore,compared with the single channel detection method,this method can significantly improve the sensitivity of detection.In this thesis,we designed and synthesized a CTB activated ratiometric fluorescent probe based on ESIPT mechanism.CTB identifies the Cbz-Phe-Lys-PABA structure of the probe molecule,and can break the amide bond between the Lys-PABA then releases the fluorescent molecule HMBT by 1,6-elimination reaction.This leads to the HMBT hydroxyl protected by state into the free state,then the configuration changes from enol to keto form.The intramolecular hydrogen bonds form,then ESIPT from "off" to "on".The emission spectrum shifts from 373 nm to 484 nm(red).Because of the over expression of CTB in cancer cells,the probe specifically releases fluorescent molecules under the action of CTB,so it can be used to detect cancer cells by using this probe.Through in vitro and cell experiments,we can achieve accurate real-time quantitative detection of CTB.In addition,the probe also has other advantages,such as a larger Stokes shift,good light stability,strong selectivity and so on.