DNA Logic Gate Based on Metallo-Toehold Strand Displacement

DNA is increasingly being used as an ideal material for the construction of nanoscale structures, circuits, and machines. Toehold-mediated DNA strand displacement reactions play a very important role in these enzyme-free constructions. In this study, the concept of metallo-toehold was utilized to further develop a mechanism for strand displacement driven by Ag(+) ions, in which the intercalation of cytosine–cytosine mismatched base pairs on the toeholds provides additional control by varying of the concentration of Ag(+) ions. The characteristics of displacement reaction in response to different concentration of Ag(+) ions are investigated by fluorescence spectral and non-denaturing polyacrylamide gel electrophoresis. The reaction can successfully occur when the concentration of Ag(+) ions is suitabe; excess Ag(+) ions block the reaction. Furthermore, the displacement reaction can be tuned and controlled most efficiently under the condition of two C:C mismatched base pairs placed on the six-nt toehold. Based on our research, a mechanism was developed to construct Boolean logic gate AND and OR by employing strand displacement reaction as a tool, Ag(+) and Hg(2+) as input.