DNA is being used to construct tiny cages, and researchers at Harvard have developed a new method of producing the largest nanocage ever crafted. 

The largest of these new structures is one-tenth the size of a typical bacterium. They are the largest and most complex structures ever made entirely from DNA. 

DNA was also used by the team to help increase the power of their equipment. Doing this provided researchers the first 3D images ever obtained of DNA nanocages in a solution. 

In nature, DNA is found in all life, directing the manufacture and behavior of proteins. By manipulating the genetic code, it is possible to "program" these strands to create new molecules. This process is called DNA origami. Short DNA strands connect two or three segments to a larger strand, creating electro-chemical forces causing the longer strand to bend or contract. 

Researchers are using this technology to build new mechanisms designed for the smallest tasks. One of the problems with progress toward this goal so far has been that previous cages were too small. The new nanocages designed by researchers at Harvard's Wyss Institute are large enough to house larger molecules. 

Peng Yin, assistant professor of systems biology at Harvard Medical School, was lead author of the paper announcing the results. Yin's team was able to construct a series of structures DNA bricks, which can be stacked like children's building blocks. They also spontaneously self-assemble, a feat not yet possible with the larger plastic toys. The size of the individual blocks is too small to encase many payloads, so Yin's team set their sights on building a larger nanocage. 

They used a photographer's tripod as an inspiration. They theorized that by attaching legs together, they could build cages piece-by-piece. As so often happens in science, practice did not match theory, and the cages produced were unstable, quickly falling apart. Like a carpenter bracing a wobbly stool, the team added a chemical strut across the wobbly strands, lending support. 

After this fix, Yin produced nanocages 60 times larger than any previous DNA cage or brick. Polyhedra produced by this procedure included cubes, triangular pyramids, tetrahedrons, and two types of prisms. 

One day, similar cages may be used to encase drugs. The cages could deliver medicine directly to the affected area. By using electro-chemical "hooks," the cage could attach itself to a protein or other structure. This could not only provide pinpoint delivery of drugs, but could be used to build microscopic factories, producing chemicals or nanobots. 

Details of the new DNA nanocages are profiled in the journal Science.  

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