Construction Of MOFs And Tb³⁺-based Fluorescence Sensing Platform And Its Application In Drug Analysi

Fluorescence sensors have the advantages of high sensitivity,good selectivity,simple operation and fast response speed.They are playing an increasingly important role in food science,biological and environmental monitoring,clinical drug analysis and other fields.Metal-organic framework（MOFs）is a new type of porous crystal material composed of metal ions（or metal clusters）and organic ligands.Compared with traditional inorganic porous materials,MOFs materials have unique characteristics such as ultra-high porosity,excellent specific surface area,and adjustable topological structure,and have broad application prospects in catalysis,drug delivery,biological imaging,magnetism and sensing,which have attracted much attention from researchers.Among MOFs,luminescent metal-organic skeletons（LMOFs）not only have outstanding optical properties but also possess the design structure and tunable chemical and physical properties.They are the potential materials that have been developed rapidly in recent years.According to different luminescence mechanism,LMOFs can be divided into three types:organic ligand-based luminescence,metal ion luminescence and guest molecule luminescence.Lanthanide metal ions(especially Eu³⁺and Tb³⁺)have high fluorescence efficiency and stable luminescence after coordination,and can be used as excellent fluorescence sensors to detect specific chemicals,so as to respond to light signals produced by the analyte.The application of LMOFs and Tb³⁺to construct fluorescence sensing platform is of great value in practical application.In this paper,three fluorescence sensors have been constructed based on MOFs and Tb³⁺and used to detect artemisinin,flavonoside and bleomycin.The specific research contents are as follows:（1）Ratiometric fluorescence detection of artemisinin based on photoluminescent Zn-MOF combined with hemin as catalyst.We designed a ratiometirc fluorescence assays for artemisinin（ART）using Zn-MOF with intrinsic fluorescence at 443 nm as fluorescence reference probe and hemin as catalyst.Hemin can catalyze the substrate o-phenylenediamine（OPD）to produce an orange fluorescence oxidation state OPD（ox OPD）as a signal probe.When OPD was mixed with hemin,a weak fluorescence signal was observed at 570 nm,which was attributed to the small amount of ox OPD production.In the presence of ART,hemin can catalyze ART to break its peroxide bridge and release a large number of reactive oxygen species,which effectively oxidize OPD into luminescent ox OPD.Therefore,the fluorescence at 570 nm is enhanced significantly while the fluorescence of Zn-MOF remains basically unchanged.Based on these facts,the ratiometric fluorescence sensing platform of ART is constructed.The method can achieve sensitive ART detection with the linear range of 0.15-150μM and the detection limit as low as 50 n M.In addition,the method has been applied to detect ART in compound naphthoquinone phosphate tablets successfully with satisfactory recovery.（2）Fluorescence sensing platform for flavonoside based on boric acid functionalized Eu-MOF.In this chapter,a functional metal-organic framework with boric acid binding site（BA-Eu-MOF）was synthesized by solvothermal method.The energy gap between the excited Eu³⁺state and the three states of the ligand3,5-dicarboxyphenylboric acid（BBDC）leads to the double emission of BA-Eu-MOF as a result of the“antenna”effect and incomplete energy transfer.The cis-diol structure of the glycogroup on the flavonoside combines with the boric acid group on BA-Eu-MOF to form a negatively charged tetrahedral borate complex.After the formation of borate bond,the“transfer metallization”reaction occurred in the system,sensitizing the“antenna”effect,reducing the cross efficiency of the sensitized Eu³⁺system,and thus weakening the fluorescence of BA-Eu-MOF at 620 nm.The sensitive detection of six flavonoid glycosides（Baicalin,Quercetin,Wogonoside,Astragalin,Puerarin and Rutin）was realized through the change of their fluorescence spectra.（3）Fluorescence sensing assay for BLM based on Ag⁺mediated DNA sensitization Tb³⁺fluorescence.We designed a guanine-rich DNA strand（G-rich DNA）that also contains the bleomycin（BLM）splice site（5′-GT-3′）.Tb³⁺interacts with G-rich DNA to form a G₄/Tb³⁺complex.Since the triplet energy of guanine overlaps with the resonant energy level of Tb³⁺,the emission of Tb³⁺is greatly enhanced.After the addition of Ag⁺,Ag⁺and Tb³⁺can bind guanine at G₄,forming G₄/Tb³⁺-Ag⁺complex and the structure of G₄/Tb³⁺is changed.The excited state of G₄is changed and the energy transfer from G₄to Tb³⁺is more effective,which enhances the luminescence of G₄/Tb³⁺.The presence of BLM-Fe（II）complex can selectively cleave the 5′-GT-3′site on G-rich DNA into several small segments,resulting in the failure of energy transfer from G₄to Tb³⁺and weakening of“antenna effect”.The fluorescence of Tb³⁺at 550 nm decreased obviously.Based on these facts,BLM can be detected sensitively ranging from 0.25-1000 n M with the detection limit of 85 p M.This method was successfully applied to the detection of human serum BLM with satisfactory results.