Hydroxyindole-based Borondipyrromethenes For Construction Of Fluorescent Probes:The Synthesis And Application

The design of reaction-based probes for discrimination between chemically closely related analysts involves conjugation of a specific recognition site to a fluorescent dye.In this paper,we report the synthesis of novel BODIPYs which have the free hydroxyl unite facile to be functionalized.Masking the free hydroxyl group with target-related triggers has led to several fluorescent probes for special biomolecules.The following is an overview of the paper:?1?The cancer specific enzyme NQO1 can be regarded as an ideal biomarker for cancer diagnosis.Herein,we designed a small molecule probe BOD-NQO1 for fluorescent assay of the activity of NQO1,which is obtained by integrating an NQO1trigger with a 6-hydroxylphenol-BODIPY platform via a linker p-aminobenzyl alcohol.Interestingly,reduction-mediated conversion of the trimethyl-locked quinone to hydroquinone led to lactonization to generate p-aminobenzyloxycarbonate,self-immolation subsequently underwent to liberate the 6-hydroxylphenol-BODIPY dye.To surpass the poor solubility of BOD-NQO1 in aqueous solution,a strategy was explored to encapsulate BOD-NQO1 into the hydrophobic interior of a polymeric micelle assembly based on an amphiphilic copolymer mPEG-DSPE.This encapsulation endowed Nano-NQO1 enhanced chemical and photo-stability,excellent aqueous solubility and biocompatibility.In the presence of NQO1,Nano-NQO1displayed favorable ratiometric fluorescence responsiveness.Furthermore,this nanoprobe has been used for discriminative imaging of NQO1-positive cells and NQO1-negative cells.?2?Near-infrared?NIR?fluorescent dyes with large Stokes shifts are attractive for construction of fluorescent probes because of the reduced autofluorescence and deep tissue penetration.However,synthesis of such organic dyes still remains a big challenge.Herein,we report the synthesis of novel BODIPYs that show NIR emission with a large Stokes shift by undergoing the excited state intramolecular proton transfer?ESIPT?.As designed,this BODIPY exhibits NIR emission at 740 nm with a large Stokes shift of>200 nm.Impressively,these optical properties remain unchanged within a range from pH 8 to approximately 5.Such promising features allow the designed dyes to be exploited as a valuable scaffold in fluorescent probes design.?3?Intracellular thiols play pivotal roles in mediating many physiological and pathological processes.Thereby,developing sensing probes for trapping these thiols is of high importance.Herein,two light-up NIR fluorescent probes for thiols were reported,wherein the hydroxyl group in NIR-BODI was masked with the acrylic and2,4-dinitrobenzenesulfonyl moieties to afford BOD-Cys and BOD-thiol,respectively.As designed,these probes showed sensitive detection of biothiols in large Stokes shifted NIR fluorescence turn-on models.Importantly,these thiol-sensitive probes are capable of visualization of thiols in living cells in NIR light-up models.?4?H₂S plays an important role in maintaining the normal metabolism of cells.It is of high scientific interest to develop molecular probes for detection of H₂S.We here designed two NIR fluorescent probes for H₂S by incorporating the azide responsive site into the fluorescent scaffold.The designed probe showed high selective response to H₂S accompanied by the liberating NIR-BODI dye,leading to significant NIR fluorescence turn-on.Moreover,such a probe has also been successfully applied in monitoring of H₂S in living cells.?5?The important roles on health and environmental issues make fluoride ion an interesting target in probe design.Herein,a novel NIR fluorescent chemodosimeter for fluoride ion was designed and synthesized.The highly specific Si-O cleavage by F^-gave the free dye NIR-BODI,thus affording NIR emission at 700 nm.We expect that such NIR turn-on response could provide a powerful tool for visualizing F^-in living systems.