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A simple tensegrity made from rods and string.  (Source: Harvard Medical School)

Folded helical DNA is held together by single strands forming a simple tensegrity structure. The light grey arrows represent the cables' contractile forces while the dark grey arrows represent the compressive forces along the struts.  (Source: Harvard Medical School)
Building a friendly nanodevice with DNA

A self-assembling nanomachine could be the dream of researchers, scientists, engineers and science-fiction writers the world over. Or it could be a reality in one Harvard Medical School's Wyss Institute for Biologically Inspired Engineering. And though the words "nano" and "machine" evoke images of tiny metal, plastic, or other bizarre material robots swimming around in your bloodstream, machinery isn't limited to these typical inanimate components.

DNA, as it turns out, makes for fantastic structural pieces and parts. The HMS and Dana-Farber Cancer Institute team constructed their self-assembling nanodevice from single-stranded DNA. They used a design principal known as tensegrity to lash double-helix struts together with single-stranded DNA. The strands interconnect the struts and pull the entire piece into a taught shape resembling a twisting prism. The structures can further be programmed to change shape on call, as well as move of their own accord.

While some nanotechnological advances are under scrutiny or fears of tampering or tainting the human body, Harvard's DNA devices will have to come under a different scrying eye. The devices are biodegradable and biocompatible. In their lives as possible drug ferries, mimicking viruses to deliver lethal drugs to targeted cells, they pose much less threat of eventual problems than solid state deliver devices such as carbon nanotubes. Once their mission is complete, the DNA machines can be safely destroyed in-vitro, leaving no troublesome refuse.

Another possible use for the DNA constructs is the fine-tuning of cellular matrices to coax stem cells into becoming one type of cell or another. Stem cells differentiate their jobs in part by the the rigidity of their surrounding tissue. Stiff extracellular matrices can convince a stem cell to produce bone, while a more liquid mixture could generate neurons. Being able to fine-tune the shapes of the DNA devices could help to control the extracellular matrices, giving stem cells a preferred environment for a desirable piece of tissue growth.

The research team has published their results in the June 20th issue of 
Nature Nanotechnology, entitled "Self-assembly of 3D prestressed tensegrity structures from DNA."





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