Design And Application Of Optical Sensing Based On DNA Hairpin Self-assembly

Deoxyribonucleic acid (DNA) is a class of important bio-macromolecule, and it is the carrier and transmitter of genetic information. The functional DNA fragments that carry specific genetic information are called genes, which have close relationship with the growth, reproduction, disease, aging and death of organism. With the completion of human genome sequencing, the research and development of drug also go into the age of genetic information, and gene-based drug become an important direction of international drug academic research. Therefore, methods for gene detection, in particular amplification methods, attract the concerns of more researchers, including drug analysis workers.Adenosine (AD) is not only endogenous nucleoside, but also the drug for the treatment of paroxysmal supraventricular tachycardia (PSVT). Adenosine plays an important role in the central nervous system, the peripheral nervous system and the immune system. In addition, adenosine is also the potential biological marker for tumor. Therefore, it has important significance to create simple, rapid and sensitive detection methods for adenosine.DNA is not only important biological macromolecule, but also a new type of biological nanomaterials. DNA molecule has unique sequence recognition function and accuracy nanometer size. Through sequence design, the self-assembly of DNA molecule can not only form the complex static structure and achieve dynamic process, but also realize signal amplification, which provide a new idea for isothermal and enzyme-free amplification.This issue design a novel optical sensing system based on DNA hairpin self-assembly, and establish a new isothermal and enzyme-free amplification method. We not only achieve enzyme-free amplification detection for the target DNA, but also realize label-free, enzyme-free amplification detection for the small drug molecule-adenosine for the first time.In chapter one, we first overview the composition, structure and detection methods for DNA, especially DNA amplification methods. Second, we focus on the research progress of DNA as new bio-nanomaterials and the application of DNA self-assembly in signal amplification. Subsequently, we summary the aptamer selection process, its characteristics and application in biological analysis. Finally, we introduce the research progress of aptasensors for adenosine.In chapter two, we design new DNA hairpin cascaded self-assembly system, and establish an enzyme-free, simple amplification method for OMP-P6gene. First, according to the length and sequence of the target DNA, we design two DNA hairpins, and label fluorophore and quencher in the symmetrical location of the stem end of one hairpin. The target DNA can trigger the cascaded self-assembly of hairpins, which makes the distance between the fluorophore and quencher increase. The fluorescence quenching efficiency decreases, and the fluorescence intensity enhances. Under the optimal reaction conditions, the target DNA has been detected:the linear range is5.0×10-9mol L-1～5.0×10-8mol L-1,the limit of detection is2.5×10-10mol L-1. The method is simple, and has good selectivity for t-DNA.In chapter three, we design new DNA hairpin catalytic self-assembly system, establish a novel label-free, enzyme-free amplification method, and realize label-free, enzyme-free amplification adenosine detection for the first time using aptamer. In order to acquire label-free fluorescence signal, we hide partial sequence of the G-quadruplex into one of the hairpins. When the hairpins are catalyzed to self-assembly, the whole sequence of the G-quadruplex is exposed, and the formed G-quadruplex can bind small fluorescent molecule, producing strong fluorescence. Under the optimal reaction conditions, adenosine has been detected:the linear range is3.0×10-5mol L-1～6.8×10-4mol L-1, the limit of detection is6.0×10-6mol L-1. The method is simple, fast, and has good selectivity for adenosine.