DNA-based molecular tagging system could replace printed barcodes

Nov. 3 (UPI) -- A new DNA-based molecular tagging system could change the way goods, from vaccines to textbooks, are tracked.

The trackable plastic tags commonly found on clothes do more than prevent retail theft.

Radio frequency identification -- and other tracking technologies like barcodes and QR codes -- helps manufacturers, logistics operators, transportation coordinators and warehouse managers keep tabs on inventory. In hospitals, tracking technologies help ensure the right medicines get to the right patients.

Though ubiquitous, these traditional methods for tracking products have plenty of flaws. Tags can be damaged or removed. For some applications, they're too bulky, impractical and not easily scaled.

Enter Porcupine, the new molecular tagging system developed by researchers at the University of Washington and Microsoft.

Buoyed by recent developments in DNA sequencing technologies and portable sensors, Porcupine utilizes dehydrated strands of synthetic DNA in place of radio frequency tags or barcodes.

Researchers suggest their solution -- described Tuesday in the journal Nature Communications -- is inexpensive and easy to use.

"Molecular tagging is not a new idea, but existing methods are still complicated and require access to a lab, which rules out many real-world scenarios," lead author Kathryn Doroschak said in a news release.

"We designed the first portable, end-to-end molecular tagging system that enables rapid, on-demand encoding and decoding at scale, and which is more accessible than existing molecular tagging methods," said Doroschak, a doctoral student at the Paul G. Allen School of Computer Science and Engineering.

Researchers used DNA strands called molecular bits, or "molbits," to produce code combinations that can be integrated into longer DNA fragments, while still being easily unraveled and sequenced later.

Different digital tags are created via the presence or absence of each of 96 different molbits along a string of binary zeros and one.

"We wanted to prove the concept while achieving a high rate of accuracy, hence the initial 96 barcodes, but we intentionally designed our system to be modular and extensible," said co-author Karin Strauss.

"With these initial barcodes, Porcupine can produce roughly 4.2 billion unique tags using basic laboratory equipment without compromising reliability upon readout," said Strauss, senior principal research manager at Microsoft Research.

By prefabricating and dehydrating the DNA strands, researchers were able to create a relatively inexpensive and secure tagging system.

The tags can be easily mixed and matched to create new codes and, because the tags are so small, they can't be easily removed, adding an extra layer of security.

"Unlike existing inventory control methods, DNA tags can't be detected by sight or touch. Practically speaking, this means they are difficult to tamper with," said senior author Jeff Nivala.

"This makes them ideal for tracking high-value items and separating legitimate goods from forgeries. A system like Porcupine could also be used to track important documents. For example, you could envision molecular tagging being used to track voters' ballots and prevent tampering in future elections," said Nivala, a research scientist at the Allen School.

To demonstrate the new system, researchers used molbits to create a tag featuring the initials of their lab, MISL. After rehydrating the tag, researchers used a portable nanopore device to successfully decode the tag.

"Porcupine is one more exciting example of a hybrid molecular-electronic system, combining molecular engineering, new sensing technology and machine learning to enable new applications," said co-author Luis Ceze, a professor in the Allen School.