Construction Of Fluorescent Carbon Nanomaterials And Fluorescent Peptide Probes And Their Applications In Sensing And Cell Imaging

In this thesis,carbon nanomaterials and peptide fluorescent materials are used as fluorescent probes,which are combined with fluorescence spectroscopy and cell imaging technology for quantitative analysis of certain substances(heparin and 2,4,6-trinitrophenol)in actual samples and multicolor live cell imaging.The carbon nanomaterials used in the thesis have many advantages like environmentally-friendliness,simplicity,rapidity,low cost,convenience,high stability and low cytotoxicity.Besides,they have high sensitivity and selectivity for detection of analytes.The rhodamine B-labeled arginine-rich peptide sequence designed in this thesis specifically recognizes heparin and is used for the construction of highly sensitive and selective sensor for heparin detection.The main contents of this thesis are as follows:Chapter 1:This chapter introduces carbon nanomaterials and peptide fluorescent materials,and systematically elaborates the research background,physical and chemical properties,general preparation methods of carbon nanomaterials and peptide nanomaterials,and their application in sensing and cell imaging.On the basis of the aforementioned introducction,we propose some design ideas,describes the research background and current status of detection of several analytes;and looks forward to the application prospects of the nanomaterials in other fields.Chapter 2:Using a convenient material,human urine,as the starting material,a one-step hydrothermal method is exploited to synthesize graphitic carbon nitride quantum dots with high fluorescence quantum yield.The morphological structure and chemical properties of the synthesized graphitic carbon nitride quantum dots were analyzed by means of UV-visible absorption spectroscopy,transmission electron microscopy,X-ray photoelectron spectroscopy,Fourier infrared spectroscopy,and fluorescence spectroscopy.The quantum dots have many merits such as good water solubility,high photostability,low cytotoxicity,and excitation-dependent emission.On the basis of these advantages,we use the fluorescent materials for cell imaging.Chapter 3:Using citric acid and adenine as starting materials,a one-step hydrothermal method is used to prepare adenine-stabilized tremella-like carbon nanosheets with high fluorescence quantum yield.The morphology and chemical properties of the synthesized carbon nanosheets were analyzed by means of UV-visible absorption spectrum,transmission electron microscope,atomic force microscope,X-ray photoelectron spectroscopy,Fourier infrared spectroscopy,and fluorescence spectroscopy.The inner filter effect between 2,4,6-trinitrophenol(TNP)and the nanosheets quenches the fluorescence,so a fluorescence quenching sensor is constructed for the detection of TNP in real samples.Chapter 4:A peptide with a specific sequence is used as the recognition unit and the fluorescent rhodamine B is used as the fluorescent output signal.A rhodamine B-labeled arginine-rich peptide sequence(RNRHTHLRTRPRK-rhodamine B)is designed as a bioreceptor for highly sensitive and selective detection of heparin.Heparin at a pM concentration can greatly quench the fluorescence of rhodamine B-labeled peptide(RBP)probes in a PBS buffer solution at pH 5.0.Through various analytical techniques(resonance light scattering,fluorescence lifetime,circular dichroism,UV-visible absorption spectrum,etc.),the fluorescence quenching mechanism of RBP probes was explored.The results showed that after the RBP was bound to heparin,the RBP containing multiple heparin binding sites underwent a conformational change from an unfolded form to a folded form,bringing the two rhodamine B fluorophores close to each other,resulting in quenching caused by aggregation.effect.Finally,the constructed biosensor was used for heparin detection in human serum samples.