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Construction Of Ratio Fluorescence Biological Probe And Its Application In Determination Of Lead Ion In Tea

Posted on:2020-09-16Degree:MasterType:Thesis
Country:ChinaCandidate:M Y LiFull Text:PDF
GTID:2381330596974764Subject:Food Science
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Tea is the traditional Chinese drink.With the pursuit of health care of tea,the quality and safety of tea has also attracted widespread public attention.Mainly related harmful microorganisms,dust pollution,pesticide residues,heavy metal pollution and other issues.The traditional detection methods for heavy metals are mainly spectrum,chromatography,mass spectrometry and so on.With the rapid development of nanomaterials science and technology,nanomaterials have a great potential in field of heavy metals and pesticide residues detection.In this paper,nanomaterials such as magnetic nanoparticles,gold nanoparticles and fluorescent quantum dots were combined with functional nucleic acids.Studies on the method of construction fluorescent nucleic acid probes for detecting lead in tea.The research content and results are as follows:The magnetic nanoparticles were carried out by a one-step polyol method.The experimental restults show that the bare magnetic beads particle size is about 100 nm.Then silicon-coated magnetic beads were synthesized by chemical modification.It particle size is about 112.8 nm.At last silicon-coated magnetic beads were functionalized by amino.The magnetic nanoparticles were characterized by Dynamic Light-Scattering(DLS)and Transmission Electron Microscopy(TEM).The experimental restults show that the magnetic nanoparticles have good uniformity,dispersion,and strong magnetism under the condition of magnetic field.Gold nanoparticles with a particle size of 10 nm was prepared by reduction of chloroauric acid with sodium citrate and NaBH4,it has a characteristic absorption peak at 519 nm by UV spectroscopy scanning.The core-shell quantum dots were prepared by using ZnS as the shell precursor and CdSe as the core layer.The fluorescence spectrum scanning shows that the quantum dots have the emission peak at 547 nm during the different time conditions.With the time from 0 to 6 hours,the fluorescence intensity increased gradually.By the UV spectroscopy scanning,a shoulder seam appeared at 400 nm.The gold nanoparticles were modified on the surface of the aminated magnetic beads.Which is capable of modifying specifically recognized thiolated DNA by means of Au-S covalent binding.The terminal of the DNA that is modified with an amino group can further decorate the carboxylation Quantum dots to form a probe with red fluorescence.And the complementary strand DNA binds green fluorescent quantum dots in the same way.Under the condition of water bath,two DNA strands are combined with hydrogen-bonded to form a dual-signal ratio fluorescent probe.By controlling the relative amounts of the two probes,incubation temperature and time,When the amount of red fluorescent probe was 150μL,the amount of green fluorescent probe was 50μL,the incubation temperature was 45℃and the incubation time was 30min.They were regarded as the conditions for the most appropriate fluorescence intensity.The single-factor experiment was used to analyze the effects of lead ion concentration,lead ion treatment time and pH conditions on the identification and regulation of ratio fluorescent probes.The experimental results were obtained as follow.The ratio fluorescent nucleic acid probe will show better sensitivity when the I540/I630value is linearly related to the logarithm of the lead ion concentration,the lead ion treatment time was 5 min and the pH condition was 9.0.in the range of 10-5μg/mL to0.1μg/mL Using different metal ions that commonly used in the laboratory,such as K+,Al3+,Ag+,Ca2+,Zn2+,Mg2+and Cu2+,it was found that the ratio fluorescent nucleic acid probe has good specificity for the detection of lead ions.Finally,the application of the ratio fluorescent bioprobe detect the actual tea sample in this experiment.
Keywords/Search Tags:Nanophase materials, Bioprobe, Ratio fluorescence, Lead ion rapid detection
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