Nanodevices hinge on DNA origami

The first demonstration of how nanoscopic components behave in the same way as everyday mechanical components could lead to much faster prototyping of nano machines than had previously been thought possible, according to US research.

"Nature has produced incredibly complex molecular machines at the nanoscale, and a major goal of bio-nanotechnology is to reproduce their function synthetically," explains Carlos Castro of Ohio State University, "Where most research groups approach this problem from a biomimetic standpoint - mimicking the structure of a biological system - we decided to tap into the well-established field of macroscopic machine design for inspiration." Now, Castro's team has used DNA "origami" to build working hinges and pistons that point to new possibilities for the construction of controllable components on an unprecedented scale. [Castro et al (2015) Proc Natl Acad Sci; DOI: 10.1073/pnas.1408869112]

The DNA origami approach was first used by other researchers in 2006 and has become a standard procedure in the development of experimental technologies in areas as diverse as molecular-scale electronics and targeted drug-delivery systems. To create more complex components than electronic components and capsules, Castro and his team have worked with Haijun Su's group to design and construct flexible motifs that can be made from single-stranded DNA and rigid parts from double-stranded DNA. Bringing together these two properties in a single component allowed for constraining motion to designed 1D, 2D, or 3D motion paths. Then actuating that motion repeatedly involved adding dangling strands that could act like "hook and eye" fasteners between parts of the component depending on the chemical surroundings.

Team members Alexander Marras and Lifeng Zhou used long DNA strands from a bacterium-infecting virus, a bacteriophage, to lock together two rigid DNA "planks" with flexible single-stranded DNA connections along one edge to create a simple hinge that could flex repeatedly. They then built a piston and cylinder system used three planks, three hinges and two tubes of different diameters - all constructed from self-assembling double-stranded and single-stranded DNA.

The team used transmission electron microscopy (TEM) to get a close look at their nanoscopic machines as well as spectroscopy with fluorescent tags to watch the shape shifting nanodevices. The hinges open and close and the piston moves back and forth, the team reports, and input of additional strands of DNA allow them to control the movements. The researchers are now hoping to expand their repertoire as well as looking at ways to scale-up production, if not the size of their machines, for further development.

We are now taking this work in a few directions," Castro told Materials Today. "One is to improve methods of controlling motion. We demonstrated that we could actuate motion of our DNA origami mechanisms on approximately minute timescales. We are now working on some new actuation methods to try to get to sub-second timescales of motion control." He adds that, "Ultimately we would like to use these types of devices to control assembly or interactions of other nanoscale objects. We¹d like to build systems where we can for example drive the function of multiple enzymes or say template a lattice nanoparticles where we can control the lattice spacing in real time."

David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase, he is author of the popular science book "Deceived Wisdom".