Redox-responsive Self-assembly Of DNA Nanostructures And DNA-assisted Assembly Of Conformation-controlled Gold-nanoparticle Clusters

DNA,an important carrier of genetic information,is also served as a unique building block with super ability of programmable self-assembly.In the 1980 s,professor Nadrian C.Seeman,who is well-known as the founder of DNA nanotechnology,proposed a magic idea that DNA molecules could be utilized for self-assembly of the precisely controlled micro-/nano-structures.Forty years later,DNA nanotechnology has grown up and became a highly interdisciplinary research field with great potentials in the applications.On the one hand,DNA molecules can be used to construct higher-ordered(static) structures,including DNA and DNA-hybrid structures.On the other hand,precise control of(dynamic) devices can be achieve based on DNA molecules,including DNA machines,DNA computing and so on.In this dissertation,we focus on two projects,which are stimuli-responsive DNA self-assembly and DNA-assisted assembly of conformation-controlled gold-nanoparticle clusters.The details are as follows:1.We have proposed a facile and universal dynamic regulation strategy for redox-responsive DNA self-assembly.Previously,realzing the redox-responsive DNA selfassmbly mostly depends on the chemical modifications of responsive units on DNA molecules,which are time-consuming and complicated.In order to develop a facile and universal regulation method,we propose a new strategy of using a redox-responsive organic molecule to regulate the dynamic DNA self-assembly.Cystamine molecule contains two amino groups and a redox-responsive disulfide bond.The doubly protonated cystamine molecules,can effectively promote DNA self-assembly.In the presence of a reductant,the disulfide bond in cystamine molecule is broken,forming two cysteamine molecules,which only has one amino group.The singly protonated cysteamine could not stabilize the higher-ordered DNA assemblies,resulting in the disassembly of DNA structures.In the presence of an oxidant,two cysteamine molecules are oxidized to be a cystamine,which could promote DNA self-assembly again.Based on cystamine,we have sussessfully constructed DNA tetrahedron,cube,two-dimensional array and rectangle DNA origami.Furthermore,we have realized the reversible assembly and disassembly cycles of DNA nanocages(including DNA tetrahedron and DNA cube)through the chemical conversion between cystamine and cysteamine.Our strategy does not rely on special DNA sequence and complex chemical modifications,which is quite facile.This strategy could also be well expanded.By utilizing some other functional organic molecules,the unique stimuli-responsive DNA self-assembly is supposed to able to be achieved.2.We have proposed a novel strategy for DNA-assisted assembly of conformation-controlled gold-nanoparticle clusters.Based on DNA molecules,a vast number of assemblies of functional units have been constructed.Howevere,it has been difficult to realize the conformation control for quite a long time in this field.Inspired by the self-assembly of DNA tiles,we proposed a facile strategy for comformation-controlled self-assembly of nanoparticle clusters.We firstly prepared the AuNP-DNA1 conjugates(there is only one DNA strand on each gold nanoparticle).Then,conformation-controlled gold nanoparticle clusters were constructed by introducing the other two strands of a DNA tile,following thermal annealing.Based on this strategy,we have assembled the tetrahedral and octahedral clusters of gold nanoparticle.Agarose gel electrophoresis and TEM have been used for the analysis and characterization.Through introducing other DNA tiles and unique nanoparticles,it should be able to construct a series of conformation-controlled nanoassemblies,providing more opportunies for the development of new materials.