Large 3D nanostructures built from Lego-like DNA bricks

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Researchers have used a DNA brick self-assembly method to build 32 different crystal structures with sophisticated 3D features (Image: Harvard's Wyss Institute)

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The very same building blocks that make us have been successfully programmed to form 32 differently-shaped crystal structures. The structures feature a precisely-defined depth and a variety of sophisticated 3D nanoscale attributes, thereby laying further foundations for the use of DNA to revolutionize nanotechnology.

The news comes courtesy of scientists at Harvard's Wyss Institute for Biologically Inspired Engineering, which previously developed a DNA-brick self-assembly method to create over 100 complex 3D nanostructures about the size of viruses. That prior work made possible the creation of these new DNA crystals, which are more than 1,000 times larger than the older DNA brick structures – large enough now that they are comparable to a speck of dust.

"We are very pleased that our DNA brick approach has solved this challenge," said senior author Peng Yin, "and we were actually surprised by how well it works."

The technique is modeled after the way in which Lego bricks interlock to build complex structures. This is possible thanks to the basic rules of DNA mixing: in forming base pairs, the A (adenine) nucleobase only binds to the T (thymine) one while C (cytosine) only binds with G (guanine). Combine many bases, changing the orientation by 90 degrees at each pairing, and you have a DNA brick.

To build their large DNA crystals, the researchers developed cuboid bricks with dimensions six helices by six helices by 24 bases that were selected to bind to the faces of other cuboid bricks. They designed four groups of crystals: one-dimensional Z-crystals and X-crystals that extended along the z axis and x axis, respectively, along with two-dimensional ZX-crystals and XY-crystals.

By combining the bricks in different patterns, they could form large numbers of distinct crystals across these categories, with simple modular design on the computer followed by self-assembly on the part of the DNA strands allowing both great precision and near infinite potential at scales up to 80 nanometers (and perhaps more in the future).

What's more, the technique could enable scalable production of new and emerging technologies, such as quantum computers. The team demonstrated that self-assembled DNA crystals made from these bricks could house gold nanoparticles inserted into slots less than two nanometers apart from each other along the crystal structure – a feat that's important for strong plasmonic coupling, which would make the technique useful in photovoltaic devices like solar cells.

The researchers expect DNA crystals to also prove useful in developing more versatile inorganic circuits and other nanoscale technologies. The technique could also aid in protein crystallography, which studies protein structures at atomic resolutions for applications in biotechnology, pharmaceuticals, and the academic field of structural biology.

"DNA nanotechnology now makes it possible for us to assemble, in a programmable way, prescribed structures rivaling the complexity of many molecular machines we see in nature," said co-author William Shih.

A paper describing the DNA brick crystals was published in the journal Nature Chemistry.

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