Robot arm carries nanoscale cargo

Taking a step toward a nanoproduction line of the future, researchers in Germany have developed a DNA “robot arm” that can move cargo from one point to another (Science 2018, DOI: 10.1126/science.aao4284). The system relies on DNA origami structures, built from strands of DNA that self-assemble into predetermined shapes. The team created a 55-nm-wide DNA origami platform and a sturdy 25-nm-long bundle of DNA helices to form an arm. One end of the arm attaches to the platform by a flexible hinge of single-stranded DNA. The platform also sports several single-stranded DNA “latches” that can grab and hold the other end of the arm as it swings around. The team then loaded the robot arm with a gold nanorod as cargo. DNA is a highly charged molecule, so the researchers manipulated the arm by varying the voltage between four electrodes placed around the DNA device. This gave them macroscopic control over nanoscale movements, enabling them to unlatch, move, and relatch the arm in a different position, along with its cargo. The process is much faster than other DNA-based cargo carriers, such as DNA walkers, which can take hours to traverse similar nanometer distances. “We can switch this in milliseconds,” says Friedrich C. Simmel of Technical University of Munich, part of the team behind the work. The group is now trying to modify the arm to enable it to pick up and deposit the cargo.