The Construction Of Ratio Fluorescence Sensor And The Detection Of Small Biological Molecules

In recent years,ratiometric fluorescence sensors have received extensive attention due to their ability to eliminate background interference,good selectivity,easy operation and high sensitivity.Small biomolecules play an important role in cell activities of life,and their content would influence the health of the living body.Therefore,detecting the content of these small molecules in the body is beneficial to the early diagnosis and treatment of diseases.In this paper,we mainly designed and constructed ratio fluorescence sensing platform to small biological molecules:glutathione and glucose.The main work is as follows:Firstly,we synthesized a dual-ligand coordination lanthanide coordination polymer GMP-Tb-luminol.GMP and luminol were chosen as two bridging ligands to coordinate with Tb3+through self-assembly,where GMP served as the antenna ligand to sensitize the fluorescence of Tb3+.The characteristic fluorescence of Tb3+can be effectively quenched by Cu2+,while the fluorescence of lumniol remains unchanged.When the target GSH is present,GSH would combine with Cu2+to form the GSH-Cu2+complex,accompanied by the fluorescelce recovery of Tb3+.The fluorescence signal of luminol was used as the reference signal.Based on this phenomenon,a ratiometric fluorescence sensor for detecting GSH was successfully constructed.We adjusted the concentration of Cu2+ to meet the different needs of sensitivity and detection range.When the Cu2+concentration was 25 ?M,the detection limit of GSH is as low as 7.38 nM,and when the Cu2+ concentration is 125 ?M,the sensor can detect higher concentrations of GSH.Secondly,a facile ratiometric fluorescence sensor for GSH measurement was designed based on MnO2 nanosheet(NS),carbon dots(CDs)and a simple substrate ophenylenediamine(OPD).Herein,MnO2 NS played triple essential roles in the sensing system.1.it could be reduced by GSH through a special reaction,and therefore served as GSH recognizer.2.it played as a fluorescence nanoquencher to strongly quench the fluorescence of CDs.3.it could directly oxidize OPD to yield a luminescent product 2,3-diaminophenazine(DAP)via the intrinsic oxidase-like activity.It revealed that MnO2 NS could be reduced to Mn2+in the presence of GSH.Thus its oxidase-like activity and fluorescence quenching abilities were inhibited,which then restricted the generation of DAP and recovered the fluorescence of CDs.Based on this phenomenon,a novel ratiometric fluorescence sensor for GSH determination was fabricated by measuring the ratio of fluorescent intensity of DAP to that of CDs.The linear range was 1 ?M100 ?M,and the detection limit was 270 nM.Finally,Ce3+ was used as the metal ion,adenosine monophosphate(AMP)and 2aminoterephthalic acid(ATA)were used as ligands to synthesize a double-ligand lanthanide coordination polymer AMP-Ce-ATA.Glucose oxidase(GOx)can be loaded into it to form AMP-Ce-ATA@GOx.Glucose was hydrolyzed by GOx in the presence of oxygen to H2O2.Then Ce3+would be oxidized to Ce4+by H2O2,the non-luminescent o-phenylenediamine(OPD)was oxidized to yellow fluorescent 2,3-diaminophenazine(DAP)by Ce4+.DAP can also quench the fluorescence of ATA through the internal filter effect(IFE).Therefore,AMP-Ce-ATA@GOx+OPD can be used to detect glucose.The sensors provided high sensitivity for glucose determination with the limit of detection as low as 40 nM and showed satisfying performance in human serum samples.