DNA nanobarrel delivers the goods

DNA origami is the folding of a single long DNA strand into any desired rigid shape, held in place by many short strands. In its original 2006 demonstration, the technique was used to make smiley faces and other whimsical shapes. Since then, researchers have developed more functional structures. Now, George Church and colleagues at Harvard Medical School have applied DNA origami to create a device that delivers a molecular payload to a specific class of target cells—an important medical goal. Their device is a barrel-shaped container, as shown in the schematic and transmission electron microscopy images in the figure, whose two halves are hinged together and fastened at the unhinged end by a pair of DNA locks. Those locks (each represented by one orange strand and one blue strand) are designed to open when they encounter particular antigens (red) that populate the surfaces of the target cells. Inside the barrel are antibodies (pink) held in place by chemically modified DNA strands (yellow). When the locks are opened, the antibodies are exposed and can disrupt or neutralize the target cells. The use of two locks is important: There may be no single antigen that uniquely characterizes the target cells, but a combination of two antigens may do the trick. It’s thanks to the DNA origami’s rigidity, unusual among nanomaterials, that the antibodies are not exposed when just one of the locks is opened. (S. M. Douglas, I. Bachelet, G. M. Church, Science 335, 831, 2012.)—Johanna Miller