pH induced reversible assembly of DNA wrapped carbon nanotubes

Both of the two DNAs with a same wrapping sequence of d(GT)20 and different free terminals showed a very high tendency to wrap around carbon nanotubes. The assembly was driven by the hybridization between the two free terminals of wrapped DNAs on the neighboring SWCNTs: i-motif (four-stranded C-quadruplex) and its complemental stranded G-quadruplex which would form tight tetraplexes and break the hybridization under slightly acidic conditions. Thus the assembly and disassembly are reversibly controlled by pH. And this assembly/disassembly process can be easily distinguished by naked eyes. Gel electrophoresis and Atomic Force Microscope are used to demonstrate the assembly and disassembly of SWCNTs at different pH.A novel pH induced reversible assembly and disassembly of SWCNTs was realized which may have potential applications in the area of controlled assembly of nanostructures.Nanostructure has potential applications in future fabricating and nanodevices [1-8]. “Bottom up” construction of exquisite nanostructure based on different kinds of nanomaterials has attracted numerous attentions [9-13]. Several studies are particularly devoted to nanostructure based on DNA and other nanomaterials such as gold nanoparticles [14,15], carbon nanotubes [16,17], graphene [18] and so on [19,20]. Nanostructures formed by single-walled carbon nanotubes (SWCNTs) and DNA combine both the size-dependent properties of the SWCNT and the molecular recognition and biological function of DNA, which have potential applications in molecular electronics [21,22] and biomedical engineering [23-25]. Both covalent [26] and noncovalent [27] associations are used to construct SWCNT–DNA complexes. However, self-assembly strategies based on the biorecognition capability of single-stranded DNA (ssDNA) have been proposed to be a promising one [16,25].Reversible assembly and disassembly of nanostructures has important function in controllable construction of nanodevices [28-30]. There are several metho