Studies On High-sensitivity Nucleic Acid Linear Threshold Gate Based On Enzymatic Cycling Amplification And The NCQDs For The Detection Of Fe³⁺

In this thesis, a novel dual amplification mechanism based on the nicking-polymerization cycling and rolling-circle amplification was performed.High-sensitivity detection of DNA was realized with such amplification mechanism. At the same time, a novel nucleic acid linear threshold gate was constructed for the discrimination of the origin of the cancer tissue based on the aforementioned mechanism. Finally, a nitrogen-doped quantum dot with stable fluorescence emission was developed. The emission of this QD can be quantitatively quenched by Fe³⁺,which can be used for the highly-sensitive detection of Fe³⁺.The research was summarized as follows:1. A high-sensitive DNA assay was developed using dual nucleic acid amplification and novel SERS enhancement substrate. The SERS substrate was constructed featuring the “gold sponge”（constructed with the bio-bar-code functioned gold nanoparticles） on home-made silver layer on the copper slips; the amplification mechanism was developed by combining nicking-polymerization cycle and rolling circle amplification. High-sensitivity detection of DNA was fulfilled using the amplification mechanism and SERS using the developed substrate, with a limit of detection under 10-16 M.2. A novel nucleic acid linear threshold gate system was constructed based on the aforementioned amplification mechanism and SERS. The design was simplified in comparison to the traditional nucleic acid linear threshold gate; and signal amplification was supplemented. Therefore, the determination of the origin of the cancer tissue based on the inputs of miRNA combination in microscale was accomplished with simplified operation and shorter operation time.3. A novel nitrogen-doped carbon quantum point was developed by carbonization of diethyl triamine penta acetic acid（DTPA）. The quantum dots exhibited stable fluorescence properties and high fluorescence intensity, and, when interacted with Fe³⁺, the fluorescence was quenched, based on which a simple stable and sensitive biosensor for detecting the content of Fe³⁺ in human serum can be established. It has potential application prospect in clinic, and it is worth to use in the diagnosis of some diseases and medical examination.