DNA folding, now sometimes known as DNA origami, is a routine way to manipulate DNA molecules into various shapes and structures. It was first put forward, in theory, in 1982 by Nadrian Seeman of New York University and proved in experiments by his team nine years later. The specific origami technique employed in the work described in this story was first developed in 2006 by Paul Rothemund at Caltech, and involves forcing a large viral genome to bend by the addition of small synthetic DNA sequences in a solution. The shorter segments attach to the main genome and act as "fastening posts" that hold the DNA in a range of shapes such as squares, triangles and, in this case, tubes that measure just 20 nm across.

Amyloid fibrils are ordered, insoluble aggregates of protein often found in patients with neurodegenerative diseases such as Alzheimer’s. The fibrils are rod-shaped and are as strong as silk (with a Young’s modulus of as high as 14 GPa for some structures). They are also stable at high temperatures, resistant to a number of chemicals and can be assembled from short, synthetic, non-disease-related peptides.

Organizing amyloid fibrils

Researchers have already used synthetic DNA molecules to form intricate structures by origami and organize other materials, such as metal nanoparticles. DNA might therefore also be used to nucleate and organize amyloid fibrils and a research group led by Seeman has now shown that this is indeed possible.

“We found that DNA origami nanotubes can sheathe amyloid fibrils formed inside them,” explains Seeman. “The nanotubes, each containing 20 helices, self-assemble thanks to the sequences of the DNA bases (A, G, C and T) and the fibrils nucleate inside the tubes via a staple strand containing a nucleating peptide.”

Scaffolds for nanobioelectronics

Once formed, the fibril-filled nanotubes can organize themselves in specific patterns onto predefined 2D substrates via DNA-DNA “hybridization” interactions. If the fibrils could be replaced with other rod-shaped structures, such as carbon nanotubes or ribbons, such platforms could then be used as scaffolds for making nanobioelectronic devices or as miniature circuit boards. Such circuits would be much smaller than those possible using conventional techniques used in the semiconducting industry.

The researchers, who report their work in Nature Nanotechnology doi:10.1038/nnano.2014.102 say that they would now like to try their hand at organizing other 1D species, such as other self-assembling peptide systems that are around the same size as the amyloid fibrils. We should also be able to organize carbon nanotubes and graphene nanoribbons in this way, said Seeman. “Indeed, interactions between amyloid fibrils and graphene may even allow us to create novel hybrid materials,” he told nanotechweb.org.