What If God Was One of Us: Scientists Use DNA to Build World’s Smallest Board Game

Team Udayavani, Dec 23, 2018, 1:45 PM IST

Scientists have created the world’s smallest tic-tac-toe board using dynamic DNA origami tiles — microscopic organic structures that can be programmed to transform into predesigned patterns.

The team from California Institute of Technology in the US had earlier used DNA origami to create tiles that could be designed to self-assemble into larger nanostructures that carry predesigned patterns.

They had chosen to make the world’s smallest version of the Italian polymath Leonardo Da Vinci’s iconic painting Mona Lisa.

However, the technique had a limitation similar to that of Vinci’s oil paints: Once the image was created, it could not easily be changed.

The team has now created tiles that are more dynamic, allowing the researchers to reshape already-built DNA structures.

Using the technique they fashioned a microscopic game of tic-tac-toe in which players place their X’s and O’s by adding special DNA tiles to the board.

“We developed a mechanism to program the dynamic interactions between complex DNA nanostructures,” said Lulu Qian, assistant professor at Caltech.

“Using this mechanism, we created the world’s smallest game board for playing tic-tac-toe, where every move involves molecular self-reconfiguration for swapping in and out hundreds of DNA strands at once,” Qian said.

Each strand of DNA consists of a backbone and four types of molecules known as bases. These bases — adenine, guanine, cytosine, and thymine, abbreviated as A, T, C, and G — can be arranged in any order, with the order representing information that can be used by cells, or in this case by engineered nanomachines.

The second property of DNA that makes it useful for building nanostructures is that the A, T, C, and G bases have a natural tendency to pair up with their counterparts.

However, a sequence can also pair up with a partially matching sequence.

The other technology, self-assembling tiles, are designed to behave like the pieces of a jigsaw puzzle. Each tile has its own place in the assembled picture, and it only fits in that spot.

In creating their new technology, the team imbued self-assembling tiles with displacement abilities. The result is tiles that can find their designated spot in a structure and then kick out the tile that already occupies that position.

To get the tic-tac-toe game started, Qian’s team mixed up a solution of blank board tiles in a test tube. Once the board assembled itself, the players took turns adding either X tiles or O tiles to the solution.

Due to the programmable nature of the DNA they are made from, the tiles were designed to slide into specific spots on the board, replacing the blank tiles that had been there.

An X tile could be designed to only slide into the lower left-hand corner of the board, for example. Players could put an X or an O in any blank spot they wanted by using tiles designed to go where they wanted.

After six days of riveting gameplay, player X emerged victorious, researchers said.

The goal of the research is to use the technology to develop nanomachines that can be modified or repaired after they have already been built.

“When you get a flat tire, you will likely just replace it instead of buying a new car. Such a manual repair is not possible for nanoscale machines,” said Grigory Tikhomirov, senior postdoctoral scholar at Caltech.

“But with this tile displacement process we discovered, it becomes possible to replace and upgrade multiple parts of engineered nanoscale machines to make them more efficient and sophisticated,” said Tikhomirov.