Controlling the adsorption and desorption of double-stranded DNA on functionalized carbon nanotube surface.

We demonstrated controlled adsorption and desorption of double-stranded DNA (dsDNA) on single-walled carbon nanotube (SWNT) surface functionalized with polyethyleneglycol (PEG SWNT). First, when dsDNA molecules were mixed with the PEG SWNT solution, the DNA molecules spontaneously adsorbed onto the PEG SWNT surface and formed dsDNA-PEG SWNT conjugates without sonication. Next, we succeeded in detaching the dsDNA adsorbed on PEG SWNT by annealing at 95°C for 30 min. These results were confirmed using atomic force microscopy, agarose gel electrophoresis, and micro-Raman spectroscopy. In contrast, when we used the usual SWNT produced by the high-pressure carbon monoxide method (HiPco SWNT), the DNA molecules were fragmented during the adsorption process as sonication was necessary for the hybridization of DNA-SWNT conjugates. Furthermore, detachment of DNA molecules from HiPco SWNT by annealing was impossible. Our method may be useful for developing DNA devices using SWNTs as substrates when it is combined with previously established various biochemical techniques.