Construction Of Track-regenerated Three-dimensional DNA Walker And Its Application In Analysis And Detection

DNA walker is a DNA nanomachine designed and prepared using DNA molecules as building elements.It can perform a series of complex operations by carrying out a controlled mechanical movement along a pre-designed one-dimensional(1-D),two-dimensional(2-D)or three-dimensional(3-D)track.DNA walkers have unique advantages,such as the ability to complete prescribed tasks autonomously without manual intervention,structural reliability,and high controllability of the system.Due to its outstanding capabilities,DNA walkers have great potential for applications in biosensing,molecular computing,cargo transportation,programmed synthesis,and logic gate design.Especially for the three-dimensional DNA walkers based on nanoparticles,the high local track concentration improves the walker’s operating efficiency,which is beneficial to the rapid release of signals.Improving the operation continuity of the DNA walker and increasing its number of steps are beneficial to accumulate more signals,thereby enhancing the performance of the DNA walker as a biosensor.Based on the above analysis,a new DNA walker with enhanced continuous operation capability was designed,and on the basis of this,a fluorescent biosensor based on DNA walker was constructed for sensitive detection of disease-related biomarkers.This thesis is divided into two chapters:Chapter one is the introduction section,which mainly outlines the construction of DNA walkers with different designs of driving forces and the application of DNA walkers in analysis and detection.Meanwhile,the scientific problems and research contents that this article mainly solves are also introduced.In chapter two,a track-regenerated DNA walker is constructed and used as a biosensor for the detection of Ebola virus gene fragment.The DNA walker is composed of gold nanoparticles(AuNP)loaded with roadbed strands and walking strands silenced by blocker,and rail strands free in solution.The roadbed strand and the rail strand combine to form the track.When the DNA walker is activated by the target,the walking strand walks along the track,and Exonuclease Ⅲ(Exo Ⅲ)cuts the rail strand in the track to release the walking strand and roadbed strand,completing one walking step.The released walking strand continues to walk,and the released roadbed strand continues to combine with the free rail strand to form a track for the walking strand to walk.In this process,with the progress of walking,a large amount of fluorescent signals are accumulated,resulting in the detection of the target with femtomolar detection sensitivity and great detection specificity.These results show that the walker has great application value in the detection of disease-related biomarkers and other aspects,and provides a potentially reliable way for the diagnosis of diseases.