Nano. Lett. doi:10.1021/nl104116s (2011)

Carbon nanotubes and DNA molecules are two of the most intensively studied materials in nanotechnology. In general they are studied separately, although there have been attempts to use DNA to sort metallic and semiconducting nanotubes, and it has been suggested that it might be possible to sequence DNA by passing it through a nanotube. Now Aleksandr Noy and co-workers have studied the motion of single strands of DNA through a nanotube in detail.

The nanotubes are embedded in a polymer matrix to prevent the DNA strands interacting with their outside surface. The strands are attached to an atomic force microscope, inserted into the nanotubes and then pulled out again. By measuring how the force needed to extract the DNA from the nanotube varies with distance, Noy and co-workers — who are based at the University of California in Merced and Berkeley, the Lawrence Berkeley Lab and Porifera Inc — are able to explore the details of the interactions between the two materials.

They find that the force needed to extract the DNA remains almost constant, which they explain in terms of the strands sliding along the inner surface of the nanotube without friction, with the force being needed to overcome the unfavourable solvation energy of the DNA. They also conclude that van der Waals forces alone cannot explain the interactions between the DNA and the nanotubes.