Development Of Highly Sensitive DNA Biosensors Bsed On Target Recycling

Nucleic acid as one of life's most basic materials was widely exists in animal and plant cells and microorganisms,In and role as amarker in biological analysis, disease diagnosis and food safety and other aspects.The development of a new method for the detection of simple design, easy operation and rapid isothermal nucleic acid sensitive areas has become the main target of nucleic acid detection and this is the main research content of this paper.In this thesis, according to target DNA analyte to build three new type of DNA biosensing platform based target recycling and autocatalytic amplification process.The realization of highly sensitive detection of nucleic acid fragments.The main contents are as follows:1.Label-free and ultrasensitive electrochemical assays of target DNA were developed. It exhibits the distinct advantages of simplicity in probe design, biosensor fabrication and detection process. A label-free hairpin DNA probe (HP1) was designed and immobilized onto a gold electrode surface, which could largely inhibit the diffusion property of [Fe(CN)6]3-/4- towards the electrode surface,to achieve the target recycle based on polymerase, this is the first step cycle.Then with the help of nicking endo-nuclease and lambda exonuclease releases the secondary target, this constitutes the recycling ?. Furthermore, it should be fairly easy to extend for the detection of a wide spectrum of analytes. Therefore, it opens a promising avenue to develop label-free and ultrasensitive electrochemical biosensors.2.Herein, a responsive hidden toehold in DNA aptamer switch to enable strand displacement reaction strategy was firstly proposed for the sensitive electrochemical detection of DNA. We designed two hairpin DNA, the introduction of target catalyzed hairpin assembly.The assembly is capable of binding with the probe on the electrode surface,the electrochemical response of ferrocene toward target DNA was achieved. The current strategies exhibited the distinct advantages of simplicity in probe design and biosensor fabrication, and enzyme-free operation. Also it should be fairly easy to extend for the detection of a wide spectrum of analytes. The currently proposed strategy could achieve the regulation of a DNA strand displacement reaction with environmental stimuli and thus open a promising approach for the future applications in bioanalysis or DNA nanotechnology.3.The use of Y-shaped probe assembly is established based on the polymerase auxiliary target circulation and ?-exonuclease digestion cycle of two-cycle strategy a simple and fast, highly sensitive fluorescence detection method achieves the target DNA. A hairpin DNA probe was designed,and In the presence of the target DNA, it can hybridize with the loop region of HP and make the HP stem open.Then the opened HP hybridize with the auxiliary DNA AP,and open the molecular beacon resulting in an evident fluorescence signal enhancement.This method is widely used in the diagnosis, treatment and medical aspects of the disease.