Researchers at McGill University's Department of Chemistry have created what may be the world's smallest "printing press." Using synthetic DNA as a kind of scaffold, the scientists manipulated gold nanoparticles a millionth of an inch in diameter to form orderly structures that could have great scientific, engineering, and medical potential.

With their peculiar optical, electronic, and chemical properties, gold nanoparticles are of great interest to scientists, but manipulating them to make best use of those properties is a bit like stirring together a load of gears and springs in a vat and hoping to get a Rolex watch.

Gold nanoparticles have been used since the Middle ages by stained glass makers, who added gold chloride to molten glass to create a ruby-red color in the glass panels. This, however, was accidental and inefficient. To unlock the more valuable properties of such nanoparticles, they need to be more organized so they can be brought close together in tiny clusters or into crystals made of up millions of particles set in a three-dimensional pattern. Not surprisingly, conventional techniques aren't up to such a task, so the McGill team hit on the idea of using DNA as an organizer – much in the same way as strands of DNA can be used to manipulate genetic material in living cells.

The idea is to use the ability of a DNA unit to pair with a complementary unit to create strands of synthetic DNA that can bond with and manipulate the nanoparticles. Up until now, this was a difficult and labor-intensive process, but the McGill innovation was to create a DNA structure that works like a printing press in a manner that is reusable, less expensive, and carries what McGill calls "unprecedented" information.

According to the team, when a gold nanoparticle encounters the structure, it comes up against strands of DNA sticking out of it that end in a sticky chemical patch. The particle sticks to this, and when the particle and DNA structure are dissolved in distilled water, the structure and the particle separate, but the strands are left behind sticking to the gold. Meanwhile, DNA structure can be used again like the letters in a printing press after a page has been run off.

The team is currently investigating the sorts of structures that can be built using this new technique. The hope is that they could have important applications, such as the ability to target cancer cells in the human body for destruction without harming neighboring tissues.

The team's research was published in Nature Chemistry.

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