An awesome paper from Shawn Douglas, Ido Bachelet, and George Church at the Wyss Institute uses DNA origami to create nanorobots that can target and kill cancer cells in a population of healthy cells. Check out the video where the authors describe their work, or stories from Nature News and New Scientist.

Douglas, S. M., Bachelet, I. & Church, G. M. "A Logic-Gated Nanorobot for Targeted Transport of Molecular Payloads." Science 335, 831–834 (2012).