Gold 'DNA Nanowires' Could Power Genetic Computers

Human beings are, in a sense, living computers built from the cell up. Is it too far-fetched to think we could build computers that way?

A team of scientists in Germany, including Bezu Teschome and Artur Erbe of Helmholtz-Zentrum Dresden-Rossendorf, are working toward that goal. They've found a way to coat DNA-based nanowires in gold and conduct electricity. Their tiny, proof-of-concept wires could lead to DNA circuits and genetic computers that self-assemble from the molecule up.

"The main advantage here is the complexity you can create on the nanoscale with these circuits," Erbe told Seeker.

Such complexity is possible thanks to a technique, called DNA origami, the scientists used to construct the nanowire. Invented in the United States about ten years ago, DNA origami involves combining a single strand of DNA in a solution with multiple shorter strands designed to bind at different sections along the single strand.

Controlling how the shorter strands bind is done by adding certain ions to the solution and adjusting the temperature. Fine-tuning these and other variables can produce two- and three-dimensional objects of virtually any shape.

"In this case, we assembled a nanotube out of DNA," Teschome told Seeker.

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It was unimaginably small, just 30 nanometers wide. For comparison, a red blood cell is about 7,000 nm across; an Ebola virus is about 1,500 nm long and 50 nm wide.

Next, the scientists used special molecules to attach gold nanoparticles and gold ions along the DNA nanotube. This wasn't too much of a headache since gold plays well with organic molecules like DNA. But after the scientists coated the nanowire in gold, they still had another hurdle.

"The main challenge with this was to connect it with the outside electrodes," Teschome said.

Making a connection from the nanoworld to the regular-sized world was critical in order to test whether the tiny wire was conducting electrons.

The scientists used a high-precision microscope to image the nanowires and then used another technique to mark where the ends of nanowires were. Next, they placed electrodes, with tips that just tens of nanometers across, on the wires. Although the tips of these electrodes are quite small, they fatten up to a micron scale, which makes them easier to handle in the regular-sized world. When the scientists tested the DNA nanowire, they confirmed it conducted electricity.

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The experiments were done at room temperatures, and the scientists noted that if the temperature fell, the charge decreased. One way to improve upon that might include adding conductive polymers between the gold particles, they reported.

But this is a first step. Tiny circuits that self-assemble from the molecule up would not only make it possible to build any shape or size computer, but it would greatly reduce the energy and cost required to create computers made from genetic material.

"Since the single building block, a single strand of DNA, is rather small, you can imagine that you could work your way down to dimensions to the single molecule regime," said Erbe. "It's difficult to imagine any top-down, lithographic strategy to go into that regime."

The research was published this week in the journal Langmuir.