Using the DNA origami method, in which complex 3-D shapes and objects are constructed by folding strands of DNA, Shawn Douglas, a Wyss Technology Development Fellow, and Ido Bachelet, a former Wyss postdoctoral fellow who is now an assistant professor in the Faculty of Life Sciences and the Nano-Center at Bar-Ilan University in Israel, created a nanosized robot in the form of an open barrel whose two halves are connected by a hinge. The DNA barrel, which acts as a container, is held shut by special DNA latches that can recognize and seek out combinations of cell-surface proteins, including disease markers. When the latches find their targets, they reconfigure, causing the two halves of the barrel to swing open and expose its contents, or payload. The container can hold various types of payloads, including specific molecules with encoded instructions that can interact with specific cell surface signaling receptors.

By combining several novel elements for the first time, the new system represents a significant advance in overcoming these implementation obstacles. For instance, because the barrel-shaped structure has no top or bottom lids, the payloads can be loaded from the side in a single step — without having to open the structure first and then reclose it. Also, while other systems use release mechanisms that respond to DNA or RNA, the novel mechanism used here responds to proteins, which are more commonly found on cell surfaces and are largely responsible for transmembrane signaling in cells. Finally, this is the first DNA-origami-based system that uses antibody fragments to convey molecular messages — a feature that offers a controlled and programmable way to replicate an immune response or develop new types of targeted therapies.

Science fiction fans have already been exposed to this idea. In his 1967 novel These Savage Futurians, Philip E. High described a "constructed micro-organism" to fight it out with viruses and bacteria.

"This object, strictly speaking, is a constructed micro-organism about the size of Hartman's virus. It is molded from special plastics, the molecules of which have been atomically arranged for durability in these conditions." He paused and almost managed a smile. "It is also a warrior robot." Again he paused and drew a deep audible breath. "Impressed on the recognition tapes of this robot is a picture of the _Metricitus spirochaeta!_" He walked over to the picture and pointed. "This pointed tube at the front of the robot is a contact device. It is designed to release on contact with the spirochaeta a lethal charge of electricity electronically restricted to a nervous system, or it you prefer it, the substance of the hostile microorganism." He turned to Judith and said, gently, "Have you followed me?"

"Yes, I've followed you." She looked puzzled.

"Judith, this auto-factory has produced sub-microscopic robots in hundred of millions. I propose injecting a few million into your blood stream in a special solution and letting them seek out and destroy the spirochaeta which are causing your illness.
(Read more about High's Sub-microscopic Medical Robots)