Construction Of Ratiometric Fluorescence Sensor And Its Application In The Detection Of Biological Small Molecules

With the development of medical technology,the abnormal expression of some biological small molecules in the body is often the marker of early warning signal of a certain disease.For example,glutathione is involved in redox reactions in the body,whose abnormal concentrations is linked to diseases such as cancer and liver damage.Accurate detection of small molecule concentration is of great significance to early disease prevention and prognosis.Ratiometric fluorescent sensor has the advantages of simple operation,easy preparation,strong anti-interference,high sensitivity and so on.It has great potential in small molecule sensing,cell imaging,p H sensing and so on.Quantum dots（QDs）with good fluorescence properties,lanthanide organometallic framework materials with good selectivity,and manganese dioxide nanosheets（Mn O₂ NS）with good oxidation properties were prepared and characterized by instruments.A ratiometric fluorescent probe was constructed using quantum dots and fluorescent Eu-MOF for determination of 6-Mercaptopurine,adenosine monophosphate and glutathione.Its main research contents are as follows:1.Ratiometric fluorescent probe based on carbon dots and Zn-doped Cd Te QDs for detection of 6-MercaptopurineA simple ratiometric fluorescence probe was prepared by utilizing two kinds of quantum dots with different emission peaks.The probe was composed of carbon dots（CDs）and Zn-doped Cd Te quantum dots（Zn Cd Te QDs）that exhibited good water solubility and fluorescence stability,with emission peaks located at 445 nm and 565 nm,respectively.The fluorescence intensity of Zn Cd Te QDs could be selectively quenched by 6-MP based on fluorescence resonance energy transfer（FRET）.Meanwhile,the fluorescence intensity of CDs basically stayed constant,and the fluorescence intensity ratio F₄₄₅ and F₅₆₅ showed a linear response to the concentration of 6-MP.The probe designed using Zn Cd Te QDs/CDs showed a broad detection range from 1.0 to 100.0μmol L^-1,with a detection limit of 0.46μmol L^-1.Furthermore,the ratiometric fluorescence probe was further applied for the detection of 6-MP in human serum samples,with RSD about 103.5%-106.0%.2.Specific Ratiometric fluorescent detection of Adenosine monophosphate based on Europium metal-organic framework and N-doped carbon dotsUsing citric acid and ethylenediamine as precursors,the blue fluorescent nitrogen doped carbon dots（N-CDs）were synthesized by hydrothermal method.The red fluorescent europium organic framework（Eu-MOF）was synthesized by using europium ion as metal center and disodium terephthalate as organic ligand.Based on the coordination between water molecules and Eu³⁺,water molecules can effectively quench the fluorescence of Eu-BDC.The fluorescence of Eu-BDC was greatly restored after the addition of adenosine monophosphate.However,neither adenosine diphosphate（ADP）nor adenosine triphosphate（ATP）could restore the fluorescence of Eu-BDC.Based on this,the blue fluorescence of CDs was used as a reference signal.A ratiometric fluorescence sensor was designed for the specific detection of AMP.Under the optimal conditions,the linear detection range of the Eu-BDC/CDs system was 1.0-80.0μmol L^-1with a detection limit of 0.25μmol L^-1.The method was successfully applied to the detection of AMP in serum samples,demonstrating its potential practical application.3.Monitoring of Glutathione using ratiometric fluorescent sensor based on Mn O₂nanosheets simultaneously tuning the fluorescence of Rhodamine 6G and Thiamine hydrochlorideL-glutathione（GSH）which has reducibility and integrated detoxification plays an important role in maintaining normal immune system function.Its abnormal levels are relevant to some clinical diseases.In this work,a facile ratiometric fluorescence sensor for GSH was designed based on Mn O₂ nanosheets,Thiamine hydrochloride（VB₁）and Rhodamine 6G（R6G）.VB₁ could be oxidized into fluorescent ox-VB₁ due to the strong oxidizing property of Mn O₂ NS,and Mn O₂ NS simultaneously could quench the fluorescence of R6G based on the inner filter effect（IFE）.Mn O₂ NS could react with GSH to form Mn²⁺,which caused its losing oxidizing property and quenching capacity.According to this principle,the concentration of ox-VB₁ diminished,resulting in its fluorescence intensity decreasing at 455 nm and the fluorescence of R6G recovering at560 nm.Under optimal conditions,the detection system of VB₁-Mn O₂ NS-R6G exhibited a wide linear range towards GSH in the range of 1.0-300.0μmol L^-1,with a low detection limit reaching 0.52μmol L^-1.The method is applicable for the determination of GSH in human serum,and is of significant importance for clinical medical diagnosis of diseases related to abnormal GSH concentrations.