The Application Of Fluorescent Carbon Dot Probes In The Detection Of Bioactive Molecules

Carbon dots(CDs)with inherent fluorescence properties are one type of"zero-dimension"carbon-based nanomaterials.They are excellent in water solubility and cytotoxicity,and their raw materials are easily available.What's more,CDs come into use in manifold fields containing bioimaging,analysis and detection,drug delivery and so on.Bioactive molecules including enzymes and amino acids are of great significance on maintaining the normal physiological function of human body.The appearance of CDs offers new tools to realize simple and rapid detection of bioactive molecules.In this thesis,the CDs fluorescence intensity changes caused by the in-situ-formed CDs or the interaction between CDs and chemical substances were regarded as a output signal for detecting cysteine,?-glucosidase,?-galactosidase and Escherichia coli(E.coli).1.Yellowish-green fluorescence carbon dots were generated by m-aminophenol and ethylenediamine under 40?water bath conditions,the quantum yield of fluorescence being 50.11%.HRTEM,XRD,FT-IR,XPS and fluorescence spectroscopy were adopted to characterize the particle size and type,functional group types,elemental content of surface,and fluorescence characteristics of CDs respectively.Hela cells CCK-8 assay of CDs indicated that the material had low cytotoxicity.Cysteine with reducing sulfhydryl group reacted with p-nitrophenyl acrylate through nucleophilic addition reaction,accompanied by p-nitrophenol formation.The inner filter effect between p-nitrophenol and CDs resulted the fluorescence to be weakened or even quenched.By means of the variation of CDs fluorescence intensity,high-specific quantitative detection of cysteine was realized.Notably,the fluorescence intensity change at 515 nm was lined with cysteine concentration increasing 1?mol/L to 50?mol/L,linear equation being y=3.82x+31.66(R~2=0.990),and limit of detection was determined to be 0.83?mol/L.Based on this method,cysteine in human serum sample was detected to be 5.16?mol/L and recovery was between 92.14%-99.51%.2.According to the characteristics of mild synthesis conditions and easy availability of raw materials of CDs,fluorescence method based on“in-situ”formation of CDs was designed to facilely detect the activities of?-glucosidase and?-galactosidase.The extent of fluorescence enhancement of“turn-on”fluorescent probe,were consistent with increasing?-glucosidase activity(0.1 U/L-60 U/L),which could deduce linear formula of y=13.48x+5.91(R~2=0.998),obtaining the detection limit of0.07 U/L.Simultaneity gave out the fluorescence change and?-galactosidase concentration in the range of 4 U/L-200 U/L the linear relationship equation of y=13.48x+5.91(R~2=0.998),calculating lower limit of detection be 3.56 U/L.?-Galactosidase could release from E.Coli cells by sonication and super-centrifugation.E.coli cells were detected based on the fluorescence of in-situ-formed CDs induced by?-galactosidase,and E.coli colony forming units could be detected at a low concentrations of 10~4 CFU/m L.The method improved performance in the detection of?-galactosidase activity(10.33 U/L)in human serum samples and supplied recovery between 97.58%-103.46%.The?-galactosidase activity in urine samples was successfully detected.The CDs formed by using different raw materials all showed excellent fluorescence performance,high sensitivity and specificity for the target analyte.They were regarded fluorescent probes to detect amino acids,enzymes and bacteria.Their appearance indicated huge application prospects in medicine,environmental science with a theoretical basis.