Researchers develop nanorobots to detect and kill cancer cells

Prof Milan Stojanovic at Columbia University, New York, developed the molecular sized robot to resemble a spider, with the ability to use its 'tentacles' for self propulsion. During its early development, it was capable of 'walking' though a field of DNA molecule, cutting and bonding with them to propel itself. By programming the environment with 'breadcrumbs', the robot was able to follow an established trail. At such tiny scales, proteins like the DNA itself remained the best bet for creating such a trail. The team found the material it needed in the work of CalTech Prof Paul Rothemund, who had invented what he named DNA origami. Using 'sequence-recognition in base pairs', DNA origami are 'folded' from a long single strand of DNA, with several shorter helper strands that 'staple' the long strand into the desired shape. Stojanovic's team made its own DNA origami bread crumbs, each measuring 2nm thick and 100nm long, programmed with a specific instruction to any walker that happens by. Together, the DNA origami bread crumbs were formed into a path that allowed Stojanovic's team to lead their DNA robots to a goal. The 4nm diameter spiders were also constructed from protein, using four symmetrically placed 'legs' that could selectively cut and bind to the DNA bread crumbs. By cutting off the protruding origami staples that tethered it, then binding to the next ones, the legs could propel the robot down the DNA path. By programming the shape of each DNA origami with specific intentions on which way the robot should go next, the researchers were able to direct the spider to follow prescribed routes. These autonomous molecular DNA robots were demonstrated to start, move, turn and stop while following a prescribed path. Applications include therapeutic medical devices that navigate by following natural DNA markers that identify cancer cells and enable the robot to deliver drugs only to those cells.