Construction Of Ratiometric Fluorescent Sensor Based On Post-modified MOF And Its Application In Biological Detection

The detection of biomolecules can directly reflect the physiological health state and facilitate health management and disease prevention.In recent years,fluorescent detection has been widely used in the sensing of biomolecules.Fluorescent detection method has the advantages of high sensitivity,high selectivity and simple operation.Most of the reported work is based on single emission intensity,which is often affected by human and environmental factors,limiting the accuracy of single-emission fluorescent sensors to some extent.Compared with single-emission fluorescent probe,dual-emission fluorescent sensors can not only realize self-calibration through the ratio of emission signal and exclude other influencing factors,but also can obtain detection results by using two or more fluorescent color changes,which improves the analysis sensing rate and also realizes real-time detection.In this thesis,a variety of ratiometric fluorescent sensors were constructed based on MOF and their applications in biosensing were studied.The specific research contents are as follows:Part One,a ratiometric fluorescent sensor based on Eu3+/Ag+modified MOF was constructed for biothiol detectionIn this chapter,using two-dimensional(2D)nickel-based metal organic framework(Ni-MOF)nanosheets as a matrix,Eu3+and Ag+were incorporated to synthesize Ag/Eu@Ni-MOF with double luminescence centers of Eu3+ ion(615 nm)and organic ligand(524 nm).And a ratiometric luminescence sensor is constructed based on Ag/Eu@Ni-MOF for sensitive detection of biothiols in aqueous solutions.The dual-emissive fluorescence properties can be tuned by changing the amounts of Ag+ions doping.The results of temperature and pH effects on the fluorescence of Ag/Eu@Ni-MOF indicates that the Ag/Eu@Ni-MOF is a temperature-sensitive material and the fluorescence of Ag/Eu@Ni-MOF can keep stable over a wide pH range.Due to the binding of-SH in cysteine(Cys)and glutathione(GSH)with Ag+,the ligand luminescence was significantly inhibited by weakening the Ag+influence on the energy transfer process in the MOFs.Therefore,ratiometric fluorescent sensing of biomolecular thiols was realized based on the dual-emission Ag/Eu@Ni-MOF.More importantly,the fluorescence color change can be observed with naked eyes to realize visual detection.The ratiometric fluorescent sensor exhibits high performance for Cys and GSH detection with a wide linear range of 5-250 ?M and a relatively low detection limit of 0.20 ?M and 0.17 ?M,respectively.Furthermore,the biothiols content in human serum was determined with satisfactory results.It proves the Ni-MOF nanosheets can be used as a stable matrix for construction luminescent MOFs for the first time,and validate the great potential of Ag/Eu@Ni-MOF as a ratiometric fluorescent probe for point-of-care testing(POCT)in disease diagnosis.Part Two,a dual-function ratiometric fluorescent sensor based on Hemin modified luminescent MOF was constructed for hydrogen peroxide detectionIn this chapter,a ratiometric fluorescent nanosensor based on heme chloride modified fluorescent metal-organic framework(NH2-MIL-53(Al)/Hemin)has been developed for the efficient detection of hydrogen peroxide.NH2-MIL-53(Al)/Hemin has dual functional properties:the 2-aminobenzoic acid ligand imparts skeleton fluorescence at 446 nm,and the loading and post-modification of heme chloride imparts skeleton peroxidase catalytic activity.The composite can react with hydrogen peroxide to produce hydroxyl radical,which can promote the conversion of o-phenylenediamine(OPD)to 2,3-diaminophenazine(DAP)with fluorescence peak at 573 nm.At the same time,the intrinsic fluorescence signal(446 nm)of NH2-MIL-53(Al)/Hemin was inhibited due to the effect of internal filtration.The ratio nanosensor has a high sensitivity to hydrogen peroxide in the range of 50-1500 ?M,with a detection limit of 36 ?M.No obvious interference of other substances to the detection of the target substance was observed.In addition,our nano-fluorescence ratiometric sensor has been proven to be useful for the accurate determination of hydrogen peroxide in the human serum environment.Part Three,a dual-function ratiometric fluorescent sensor based on carbon quantum dot loaded MOF was constructed for cholesterol detectionIn this chapter,a ratiometric fluorescent nanosensor based on carbon quantum dots supported iron organic framework(CQDs@MIL-101(Fe))was constructed for the efficient detection of cholesterol.The successful loading of carbon quantum dots at 455 nm gives the fluorescence characteristics of the composites.When cholesterol oxidase is introduced to hydrolyze cholesterol to produce hydrogen peroxide,the fenton reaction between MIL-101(Fe)and hydrogen peroxide produces hydroxyl radical,and then oxidizes o-phenylenediamine(OPD)to produce 2,3-diaminophenolazine(DAP)with yellow fluorescence.At the same time,the intrinsic fluorescence signal of CQDs@MIL-101(Fe)is inhibited due to the effect of internal filtration.The ratio nanosensor has high sensitivity to cholesterol in the range of 5-100 ?M and 100-1000 ?M,with a detection limit of 4.55 ?M.In addition,our nanosensor has been proven to be useful for real-time monitoring of total cholesterol(TC)in human serum.