Construction Of A Carbon Dot Based Ratiometric Fluorescent Probe And Its Application In Intracellular Formaldehyde Imaging

Formaldehyde is a common carcinogenic and teratogenic substance,which has been identified as a potential allergy source by the World Health Organization.As a chemical pollutant,the pollution of the indoor air atmospheric,environment and food caused by formaldehyde can lead to formaldehyde poisoning,dizziness headache,nausea vomiting serious memory loss and even death.In most biological organisms,some amino acids and exogenous substances,under the catalysis of demethylase or oxidase,metabolize and produce endogenous formaldehyde.However,more than a certain amount of formaldehyde in the human body can lead to many diseases,including Alzheimer’s disease,neurogenic inflammation,diabetes,chronic liver disease,cardiovascular disease and cancer.Because of the widespread presence of formaldehyde in industrial environments and household goods,several methods have been designed for the detection of formaldehyde,including the use of high performance liquid chromatography(HPLC),gas chromatography(GC),mass spectrometry(MS)and preconcentration/chemical ionization mass spectrometry.However,the physiological function of formaldehyde is still unclear.This paper aims to construct a fluorescence ratiometric probe with high selectivity and detection performance for the detection and imaging of formaldehyde in cells.In the first chapter,the harm,source and detection method of formaldehyde are introduced.The preparation method and sensing application of carbon dots are reviewed,and the fluorescence ratiometric probe is briefly introduced.In the second chapter.a nitrogen-doped fluorescent carbon dots was prepared from citric acid and methionine.The carbon dots and ratiometric probe are characterized by UV-Vis absorption spectrum,fluorescence spectrum,fourier transform infrared spectroscopy(FT-IR),transmission electron microscope(TEM),X ray diffraction(XRD),and X ray photoelectron spectroscopy(XPS).The results of transmission electron microscope and X-ray diffraction show that the carbon dots are amorphous and their average size is 10.57±0.80 nm.Fluorescence analysis shows that their luminescence is dependent on excitation wavelength and their fluorescence is stable at different pH values.The size of the ratiometic probe is 10.78±0.78 nm.UV.FT-IR and XPS show that organic molecules are successfully connected on the surface of carbon dots.In the third chapter,the detection ability of ratiometric probe to formaldehyde in aqueous solution and its imaging ability in cells are studied.It is found that the probe has high selectivity and low detection limit for formaldehyde detection in aqueous solution(0.34μM),and keeps stable at high salt concentration.Further application in cells show that the probe has low cytotoxicity and good biocompatibility.Laser scanning confocal microscopy is used to detect endogenous and exogenous formaldehyde.Colocalization studies show that the probe can target lysosomes.Furthermore,the way of cell uptake material and the reason that the probe targeted lysosomes are investigated.The dual-emission ratiometric probe has excellent performance and good prospect of application.