Control Of Interaction Between DNA And Gold Nanoparticles And Their Assembly

As the carrier of genetic information,DNA is a macromolecule whose molecular weight can be precisely regulated and can be artificially designed and synthesized.Owing to its sequence-binding specificity and programmability,DNA can drive the assembly of gold nanoparticles(AuNPs).The research on DNA-functionalized AuNPs(DNA-AuNPs)has not only enabled the multifunctional design and fabrication of dynamic DNA nanodevices,but also enriched the development of nanotechnology.In this dissertation,DNA-AuNPs system was taken as the model system to systematically study the effects of different kinds of salt,salt concentration and pH on the interaction between DNA and AuNPs.By regulating the interaction between DNA and AuNPs,stable DNA-AuNPs were prepared,which were applied to construct molecular machines and simulate chemical reactions.Subsequently,the critical percolation state of the DNA-AuNPs assembly were constructed,and the assembly behavior of DNAAuNPs was regulated by an electric field.The specific content and results are summarized as follows:1.Regulation and stability of DNA-AuNPs interactionThe stability of polyadenine(polyA)-DNA-AuNPs limits its application in the construction of DNA molecular machines.The amine groups and nitrogen atoms on the A base ring have strong non-covalent interactions with AuNPs,and the A bases can be adsorbed to the surface of AuNPs by replacing the capping agent citrate on the AuNPs.The effects of different kinds,different concentrations of salt and pH on the stability of polyA-DNA-AuNPs were studied,and the stable polyA-DNA-AuNPs were used to construct DNA molecular machines.It was found that high salt and low pH value contribute to the stabilization of polyA-DNA-AuNPs due to the coordination of electrostatics and multiple interactions.The polyA-DNA based molecular machine made of A9-DNA-AuNPs incubated in pH 3.0 solution had optimal efficiency when the catalyst oligomer concentration was 50 nM.2.Bridge DNA guided assembly of nanoparticles to program chemical reaction networksA bridge DNA guided assembly of AuNPs was constructed to simulate one-step and multi-step chemical reactions.In the one-step reaction programmed by bridge DNA,the reaction rate of was investigated by changing the ratio of the two kinds of grafted DNA on AuNPs and the ratio of AuNPs and bridge DNA.The effect of toehold length on the reaction rate of multi-step reactions was investigated in depth.In the one-step reaction driven by bridge DNA,the optimal rate of reaction was obtained when the ratio of AuNPs and bridge DNA was 1:10.A six-base toehold is enough to achieve the toehold-mediated strand displacement reaction in bridge DNA.When the difference between toehold length-2 and toehold length-1 is equal to or larger than one,the multistep reaction can be triggered and performed by the driving of bridge DNA.3.Electric field-regulated assembly of DNA-AuNPsA strategy for electric field-regulated DNA-AuNPs assembly is proposed.Consider the DNA-AuNPs,as an elementary structure,and regulate the interaction between DNA and AuNPs to form a percolation state.Through the regulation of voltage and frequency,the superlattice structure was formed.The study showed that under the effect of an alternating voltage of 4V(with a plate spacing of 1mm)and a freqency of 300 kHz,the disordered aggregates of DNA-AuNPs in a critical percolation state could be further assembled into ordered superlattices.and DNA was successfully realized.As a result,the assembled structure of DNA-AuNPs was regulated from disordered aggregates to ordered superlattices successfully.The work of this dissertation has deepened the understanding of the interaction between DNA and AuNPs,and enriched the preparation and regulation methods of stable DNA-AuNPs complex and their assembly.