The switchable pH-driven reversible assembly and dissociation of interlocked circular DNA dimers is presented. The circular DNA dimers are interconnected by pH-responsive nucleic acid bridges. In one configuration, the two-ring nanostructure is separated at pH = 5.0 to individual rings by reconfiguring the interlocking bridges into C-G·C(+) triplex units, and the two-ring assembly is reformed at pH = 7.0. In the second configuration, the dimer of circular DNAs is bridged at pH = 7.0 by the T-A·T triplex bridging units that are separated at pH = 10.0, leading to the dissociation of the dimer to single circular DNA nanostructures. The two circular DNA units are also interconnected by two pH-responsive locks. The pH-programmed opening of the locks at pH = 5.0 or pH = 10.0 yields two isomeric dimer structures composed of two circular DNAs. The switchable reconfigured states of the circular DNA nanostructures are followed by time-dependent fluorescence changes of fluorophore/quencher labeled systems and by complementary gel electrophoresis experiments. The dimer circular DNA structures are further implemented as scaffolds for the assembly of Au nanoparticle dimers exhibiting controlled spatial separation.
Keywords: Nanotechnology; fluorescence; nanoparticle; switch; triplex.