Research On The Biosensors Of Radioactive Radon And Heavy Metal Ions Based On Functional Nucleic Acid And Metallothionein-gold Nanoclusters

Radon is a colorless,tasteless,odorless,radioactive inert gas that emits?-rays and?-rays and is widespread in living environments and workplaces.Radon has become the main indoor radioactive gas pollutant and the major radioactive gas causing harm to humans.In recent years,heavy-metal pollutants that harm humans have also become increasingly problematic.Lead ion is a potential poison that can cause serious harm to the central nervous system and the hematopoietic system.Mercury ion is a heavy-metal contaminant that damages the kidney,brain,and endocrine system.Therefore,a new method with high sensitivity,high accuracy,good reliability,simple operation,and low cost that does not pose a radiation hazard is urgently needed for the detection of heavy-metal ions and radon.In Chapter 1,the significance and research status of radon and heavy-metal ion detection are summarized and the concept and application of DNAzymes and gold nanoclusters in analytical detection technology are described.The main contents of this paper are also briefly introduced.In Chapter 2,a new sensitive,novel and indirect detection strategy for radon is proposed.This strategy combines the signal amplification strategy of DNAzyme and G-quadruplex and utilizes the horseradish peroxidase activity of the G-quadruplex with hemin.In the experiments,lead ions trigger the enzyme,cleaving the base chains,and the sheared primer chains dissociate in solution.When the stem ring probe Hp1 or Hp2,which contains G-rich sequences,is added,part of the Hp1 is complementary to the free substrate chain to form a double-helix segment induced by the primer chain.After G-quadruplex binds to the hemin,G-quadruplex with horseradish peroxidase catalytic activity is formed.This G-quadruplex catalyzes the reaction of the oxidation substrate and changes the UV absorption behavior.The detection sensitivity was improved via the loop reaction strategy of the enzyme base chain:the detection limit of lead ion was 0.775 nM,and the detection limit of radon reached 1.76×10³ Bq·h/m³.In addition,the mechanism of this reaction was studied by UV spectroscopy,and circular dichroism spectroscopy.This new indirect method is accurate and sensitive and avoids direct exposure to radon.The method opens a new field of biological analysis of heavy-metal ions and radioactive gases by circulating amplified signals of the free primer chain.In Chapter 3,a novel metallothionein-templated gold nanocluster?MT-AuNC?material is synthesized and its synthesis method is briefly described.Based on the characteristic that Pb²⁺and Hg²⁺can quench the fluorescence of MT-AuNCs under different reaction conditions,a simple,accurate and green fluorescence method based on MT-AuNCs is established to detect Pb²⁺and Hg²⁺,respectively.The reaction was characterized by transmission electron microscopy,infrared spectroscopy,and X-ray photoelectron spectroscopy.Compared with gold nanoparticles,nanoclusters are smaller,have better water solubility and biocompatibility,and have good fluorescence properties.MT-AuNCs can function as a fluorescent alternative to toxic organic fluorescent dyes for the detection of heavy-metal pollutants.Their use in biomedicine,cellular imaging and biomarker detection is expected to expand.AuNCs have broad application prospects and provide new approaches for clinical diagnoses,biomedical research,and the detection of environmental pollutants.In Chapter 4,a new method for the detection of lead ion is studied based on the signal enhancement of the novel fluorescence probe tetramethyl benzidine?TMB?.TMB is a commonly used chromogenic agent,but its fluorescence properties have rarely been exploited.The experimental results show that the fluorescence intensity increases with the increasing lead ion concentration and that the detection limit of Pb²⁺is79.9 pM,with a lead ion concentration range from 0.266 nM to 12 nM.The reaction mechanism was studied by fluorescence spectroscopy and infrared spectroscopy.This method has the advantages of high sensitivity,simple operation,low equipment costs,and rapid detection.This strategy is expected to lead to the development of a sensitive,simple,and rapid method for the detection of heavy metals.