The Construction Of Fluorescent Carbon Dots Sensors And Their Application In Enzyme Activity Detection

As a kind of nano carbon particles with dispersibility,carbon dots（CDs）have the advantages of excellent fluorescence properties,high water solubility,stability and good biocompatibility,non-toxicity,environmentally friendly,low cost.In recent years,CDs have been widely used in the field of materials science,biology and medicine.Biological enzymes are closely related to many diseases of the human body and have been widely used for medical diagnosis in recent years.The use of simple and fast chemical methods to detect biological enzymes has provided new ideas and methods for the diagnosis of medical diseases.In this thesis,fluorescent nanomaterials were systhesized under mild conditions and used as biosensors with enzyme as a biological sensitive unit to construct highly selective detectors to target analytes.1. A sensitive nanocomplex probe prepared fromfluorescent polydopamine nanoparticles（F-PDA）and cobalt oxyhydroxide（Co OOH）nanosheets was established for the determination ofα-glucosidase activity.In this detection system,α-glucosidase activity was successfully determined by a“turn-on”mode taking the advantage of the fluorescence resonance energy transfer（FRET）between F-PDA and Co OOH nanosheets.This fluorescent method showed a good linear relationship with the activity ofα-glucosidase from 2 to 80 U/L and a low detection limit of 1.65 U/L.This fluorescence probe with high selectivity and sensitivity demonstrated applicability in human serum samples and provided an alternative forα-glucosidase inhibitors screening in the discovery of anti-diabetes drugs.2. CDs were synthesized from p-aminophenol and ethylenediamine via one-stepunder reflux at 50℃.They were used as sensitive fluorescent nanoprobes for the activity determination of NAG activity,TYR activity and the concentraton of kojic acid based on the inner filter effect between on CDs and p-nitrophenol or melanin mimics.Both assay showed high specifity and sensitivity.The assay for NAG activity provided a low detection limit of 0.75 U/L and showed a good linear relationship in the range from 1 to45 U/L.There was a good linear relationship between TYR activity and fluorescence intensity in the range of 10-400 U/L,and the detection limit was as low as 8.96 U/L.This method was successfully used to the detection of TYR enzyme in potatoes and apricot mushrooms and the concentration of kojic acid,which provided good results.3. CDs was synthesized by hydroquinone and ethylenediamine under heating condition,and a CDs-EPA fluorescent probe sensor was constructed to detect blood glucose in serum.Glucose is catalyzed by glucose oxidase（GOX）to generate hydrogen peroxide（H₂O₂）,which oxidized N,N-diethyl-p-phenylenediamine（EPA）to ox EPA.The purpose of detecting the glucose concentration was achieved by the decrease in the fluorescence intensity of CDs caused by a fluorescence energy resonance transfer（FRET）between CDs and ox PEA.The detection method was simple,sensitive and accurate.There was a good linear relationship between fluorescence intensity and glucose concentration in the range of 0.5-125μmol/L,and the detection limit was as low as 0.35μmol/L.The probe was accurately applied to the detection of blood glucose concentration in human serum sample.Fluorescent nanomaterials were synthesized with simple method and were used in the fluorescence detection system to realize the quantitative detection target analyte based on the interaction between the nanomaterials and different compounds.All the detection system showed high specificity and sensitivity.They provided a theoretical basis for the further application of fluorescent nanomaterials in biology,medicine and pesticide study,which embodied their application prospects in biological medicine,food testing,and pesticide science.