Construction Of Fluorescent Probe Based On CDs And Its Application In Biosensors

ObjectiveThis thesis aims to design and synthesize two types of fluorescence probes based on carbon quantum dots(CDs)for detecting biological thiols and p H values,respectively.The application of these probes in biological systems will be investigated in order to obtain fluorescence probes with high selectivity,strong anti-interference ability,high sensitivity,and good imaging and detection capabilities for biological thiols or p H values in the biological system.Methods(1)Carbon quantum dots were prepared from resorcinol by reflux method,and biological mercaptan fluorescence probe CDs-CNPMD was prepared by chemical derivatization combined with recognition group.The structure and functional groups of the probe were characterized by TEM,XRD,IR and XPS;Ultraviolet-visible spectrum and fluorescence spectrum were used to investigate and establish the probe in the selective recognition of biological mercaptan.The cytotoxicity of the two probes was studied by CCK-8 method;Finally,the imaging ability of the probe to biological mercaptan in cells was investigated by fluorescence microscopy.(2)R-CDs forp Hsensing were prepared by microwave method with m-phenylenediamine as raw material.The morphology,crystallinity and surface functional groups of R-CDs were characterized by TEM,XRD,IR and XPS;The ultraviolet absorption and luminescence behavior of R-CDs under differentp Hand solvent conditions were studied by using FL and UV-vis spectra.On this basis,the luminescence mechanism of R-CDs and the formation mechanism of R-CDs were studied by using fluorescence lifetime,Zeta potential,TLC and HPLC;The selectivity of R-CDs top Hsensing and the ability to resist interference of other ions and amino acids were investigated.The proliferative toxicity of R-CDs was studied by MTT method;For cell imaging,the cells were inoculated on a six-well plate,and R-CDs with differentp Hvalues were added to each well.The imaging ability of R-CDs to bacteria and cells at differentp Hwas studied by fluorescence microscopy.Results(1)The probe CDs-CNPMD has high selectivity and anti-interference ability for the detection of three biological mercaptans.The linear detection range for the three biological mercaptans is 0-30 μM,and the detection limit is 1 μM.The probe has no obvious toxicity to A549 cells.The cell imaging experiment showed that the probe CDs-CNPMD could selectively image the biological mercaptan in cells.(2)The diameter of the prepared R-CDs ranged from 2.03 to 4.71 nm,with an average diameter of 2.97 nm.R-CDs have graphite-like structure.The surface structure of R-CDs includes pyridine N,graphite N and amino group.R-CDs have a high quantum yield of 18.9%.R-CDs have sensitive sensitivity to p H.In water,thep Hdetection range of R-CDs is 1-5,and p Ka is 2.55.High ionic strength and long ultraviolet irradiation time have no obvious effect on the fluorescence intensity of R-CDs.After incubating A549 cells with different concentrations of R-CDs for 24 hours,more than 82% of cell viability was observed.In the cell imaging experiment,the cells showed relatively strong fluorescence emission atp H2.0,the fluorescence intensity was significantly reduced atp H3.0,and almost no fluorescence was observed atp H7.4;Similar results were observed in E.coli.ConclusionsBased on carbon quantum dots,two fluorescent probes have been successfully developed for the detection of biological mercaptan andp Hvalue in biological systems.Both probes have excellent selectivity,anti-interference ability and biocompatibility.The cell imaging experiment showed that the probe CDs-CNPMD had good imaging ability for the biological mercaptan in cells;The probe R-CDs has good imaging ability for the lowerp Hof cells and Escherichia coli,and has good potential for application to biological systems.