Scientists from Columbia University, Arizona State University, the University of Michigan, and the California Institute of Technology (Caltech) have created a robot that’s just 4 nanometers wide. And no, it doesn’t have flashing lights, video cameras or wheels. It does, however, have four legs, and the ability to start, move, turn, and stop. Descendants of the molecular nanobot, or “spider,” could someday be used to treat diseases such as cancer or diabetes.
The team built the spider by starting with a protein called streptavidin, that conveniently has four symmetrically-placed binding pockets for a chemical called biotin. The legs were made from four strands of biotin-labeled DNA, which were bound to the pockets. Three of the legs were made from enzymatic DNA, which is a type that binds to and then dissociates (cuts away) from other particular sequences of DNA. Its fourth leg was made from what the researchers call a “start strand” of DNA – it keeps the spider tethered to its starting site, until it’s released.
Like a traditional robot, the team wanted the spider to be able to sense its environment, make a decision, and then act on that decision. Given that it was much too small to incorporate any kind of processor, however, its programming would have to come from outside its body. To accomplish this, the team had to adapt the spider’s environment to provide the instructions. They started by taking a single long strand of DNA and used shorter DNA strands to “staple” it into a two-dimensional rectangular shape. This would be the rectangular track that the spider was placed on, and had to follow.
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