Research On Electrochemiluminescence Sensing Method For Micro RNA Determination Based On Signal Amplification Technology

In recent years,the number of new cancers has risen sharply,and the number of deaths has increased year by year.Cancer has seriously endangered human health.In addition,people often have advanced cancer when they are found to have cancer,and advanced cancer treatment is expensive and difficult to cure.Therefore,early detection and early treatment are particularly important,but there is still a lack of ideal early diagnosis methods with strong specificity.MicroRNAs（miRNAs）are a class of conservatively evolved,endogenous,tiny single-stranded non-protein-coding nucleotide molecules,usually 19-23 nucleotides in length.They are involved in the regulation of post-transcriptional gene expression in a variety of biological processes and are considered to be key biomarkers for early diagnosis of various cancers.The detection of miRNA can determine the presence of tumors,disease progression and prognosis.Therefore,the quantitative detection of miRNA is of great significance in the diagnosis and treatment of cancer.At present,a variety of detection technologies and quantitative detection of miRNA are used,including fluorescence,electrochemistry,and photoelectrochemistry.However,due to the original characteristics of miRNAs,such as small size,low abundance,and high similarity between family members,the accuracy and sensitive detection of miRNAs are still challenging.Therefore,in order to solve the above problems,we prepared different quantum dots to detect miRNA.The main research contents of the thesis are as follows:1.First,we prepared a new type of quantum dot MZnAgInS/ZnS and combined it with S2（S2-MZnAgInS/ZnS）.After Hairpin DNA 1（H1）was fixed on the electrode surface,DNA-Walker and H2 were added to turn on H1,and the walking machine started to walk.Then S2-MZnAgInS/ZnS combined with the opened H1 to generate light.Since the generated DNA-Walker was proportional to the concentration of miRNA-19a added,this ECL biosensor could be used to detect miRNA-19a.2.Boron nitride quantum dots（BNQDs）were prepared by hydrothermal method,and nano-silver（AgNPs）and nano-gold（AuNPs）were prepared.After simple self-assembly PDDA/PSS film on glassy carbon electrode,boron nitride quantum dots are drip-coated on the electrode,then single-stranded DNA（S1）is modified on the BNQDs,and then the S2-AgNPs couple is introduced.Combines to quench the luminescence of BNQDs.After miRNA-141/H1-MB was added,the S2-AgNPs bound to S1 on the BNQDs were taken away to restore the luminescence of the quantum dots.The finally added H2-AuNPs would be covalently coupled with S1 to enhance the luminescence of the quantum dots.So as to achieve the purpose of detecting miRNA-141.Use HRTEM,UV-vis,PL and other methods to characterize the morphology,structure and composition of nanocomposites,and characterize this biosensor by CV method.The research results showed that the biosensor has good specificity and reproducibility,has a high detection line and a good detection limit.3.First,we prepared boron nitride quantum dots（BNQDs,as ECL emitters）and mesoporous nano-silica（MSNs,as molecular gating systems）.After that,BNQDs were coated on the cathode of the bipolar electrode（BPE）,and another ECL material picolinoyl iridium（Ir（df-ppy）₂（pic）,abbreviated Firpic）and the co-reactant tripropylamine TPr A)Calibrate the anode of the BPE.Then,the hairpin DNA（H1）was effectively bound to the surface of MSNs through the action of chemical bonds to form a DNA-MSNs conjugate,which modified on the surface of BNQDs to control the release and release of glucose trapped in the pores of MSNs.freed.In the presence of target miRNA-21,miRNA-21 will bind to H1,opened the hairpin structure of H1,and released glucose in MSNs blocked by H1.Glucose reacted with glucose oxidase（GOD）to produce H₂O₂,which reduced the ECL signal at the cathode.On the other hand,due to the reduction of H₂O₂generated at the cathode,the Faraday current flowing through the BPE increased,and the corresponding ECL signal of Firpic at the anode is promoted.Finally,in the presence of K⁺and heme,the unreacted bases of H1form a G-quadruplex,which catalyzes the formation of OH^-from H₂O₂.The consumption of H₂O₂restores the ECL of the cathode,the catalytic reduction of H₂O₂further increased the Faraday current of the BPE,and the ECL of the anode becomes stronger.Based on the above concepts,the concentration of miRNA-21 can be determined by the ratio of the ECL intensity of BNQDs and Firpic.