Next time you buy a designer shirt, be sure to check the label. What you don't see may surprise you. Hidden within the ink or fibers of that shirt could lie an authentication device made not of plastic or metal, but of DNA.

"DNA has become the gold standard, the highest barrier to product counterfeiting, diversion, and piracy," says Julia Hunter, executive vice president of Applied DNA Sciences in Los Angeles. In this case, though, the term gold is both literal and figurative. The International Chamber of Commerce estimates that 7% of the world's trade goods at any given time are fakes, draining $350 billion (US) annually from legitimate businesses.

Though DNA security methods are too new to have yet been pivotal in convicting counterfeiters in court or breaking up fraud rings, it is only a matter of time. Hunter and the technology's other champions envision unique DNA markers being...


Given scientists' long struggle to understand DNA's secret language, perhaps it is not surprising that some researchers are developing a renewed appreciation for the dialect's impenetrability.

Consider the experience of the 2000 Sydney Summer Olympics. DNA Technologies of Halifax, Nova Scotia, tagged 34 million labels with unique DNA strands. The labels then were attached to officially licensed Olympic merchandise. Later, of 3,422 on-the-spot inspections, 507 (14.8%) turned up counterfeit products, with 77% of the discovered violations occurring within the first three months of the three-year sales program.

The Sydney Olympic Committee estimated that "revenues lost to counterfeiting were under one percent" of total sales, netting the games an additional $700,000 in royalty income. In contrast, the Atlanta games committee in 1996 estimated that as much as half of its merchandise sold around the world was bogus.

Genetic markers could be used to track a product's provenance as well as its authenticity. For a pittance per pound, individual cows could be tattooed with inks containing unique DNA identifiers that reveal their pedigree and health history. If one of these animals were to come down with mad cow disease, enforcement officials could track its origins and siblings, using the presence or absence of the distinctive DNA to determine whether the tattoo was forged or genuine.

The consequences of counterfeiting can be far more serious than a loss of money. "If you buy something you think is an Armani suit and it's really not, that's not a very big deal," says Chris Outwater, vice president of technology for DNA Technologies. "But you care that your heart medication is the real thing."

And in the United States and abroad, imitation drugs can be a real problem. The World Health Organization calculates that 10% of the drugs on pharmacy shelves are counterfeit, a figure that can rise to 60% in developing countries. The US Food and Drug Administration has uncovered birth control pills made of wheat flour, tap water disguised as meningitis vaccine, and acetaminophen that was actually a concoction of industrial solvents. Phony AIDS medications were discovered in the United States in 2001. During the two preceding years, 16 Americans died when given a fake antibiotic that further debilitated rather than helped them.

Some experts say DNA might represent the best defense against such mischief. "DNA is the only known physical marker that can be made so complex that it can't be counterfeited," Outwater says. His firm uses a proprietary process to physically structure its DNA markers to render them unrecognizable by standard DNA reading and replication techniques. "Finding out what kind of DNA a marker is made from or how to copy it would take so much time and cost that the effort would hardly be worth it."


In principle, the process of tagging products with a DNA authenticator is straightforward. A strand of DNA, anywhere from 20 to tens of thousands of base pairs long, is either synthesized or extracted from a plant's genome and assigned as a unique identifier for a line of shirts or soccer balls or some other product. The DNA is then replicated by PCR and mixed with the ink used to print the product's label or packaging.

Alternatively, the DNA can be sprayed onto a product as a film, embedded in thread or powder coatings, or simply stirred into other compounds such as pharmaceuticals. The tag can be embedded in the ink that prints a label, on a certain point along the label, in a specific stripe of bar code, in the thread that stitches a shirt's left cuff, or anywhere else the manufacturer desires. The product, its DNA tag, and the location of that tag, become a unique combination.

To determine whether a dress is the genuine article or a truck's brake part is authentic instead of a shoddy knock-off, inspectors apply the reverse complement of the DNA strand that the product in question should bear in the location where it should lie. Only a perfect match sparks a telltale fluorescent reaction that authenticates the product's pedigree.


But the process can be tricky. Most commonly, the DNA strand is mixed with ink used to print labels or packaging. "There are hundreds of kinds of inks, many water-based, many others solvent-based, and DNA goes differently into each kind," Outwater explains. "A lot of our time has been invested in learning how to mix DNA with inks, how to keep it in the ink, and how to retrieve it once it's imprinted and dried on a product."

DNA security specialists have also had to become experts in the behavior of DNA in printing processes such as offset and silkscreen. "This has been our most demanding task," says chemist Georg Bauer, managing director of Identif Technologies in Erlangen, Germany.

Protecting the DNA itself is key. Companies have developed an array of coatings in which to encase their DNA markers to protect them from handling, scouring, harsh chemicals, ultraviolet light, and the other assailants that DNA can fall prey to. Bauer describes his company's proprietary coating as a "clear varnish." Outwater says his firm has been experimenting with a "protein casing." chemical shield surrounding Applied DNA Science's tags is not only more elaborate, but also only one of the measures the company takes to guard its DNA markers from detection.

First, the company selects a DNA sequence from its catalog of thousands of plants, then chops it up and stitches it back together in a unique and deliberate way. The coating not only renders the DNA invisible to ordinary scanners, but also irretrievable by anything other than the firm's proprietary chemical detection process. "Breaking open the coating shatters the DNA into random pieces," Hunter explains. "Counterfeiters can't copy our DNA marker because they can't open it without destroying it."


The task of determining whether a tag is present belongs to company scanners, all of which work in much the same way. "It's a laboratory wet process," explains Outwater. First, the firm's technicians check the product itself for the presence of an optical tag in the form of luminescent molecules attached to the DNA marker. "But those can be more easily counterfeited than the DNA itself," he adds.

The next step is to use buffers and centrifuges to separate the marker from the ink, then replicate the DNA by standard PCR. "When we have enough, we can probe forensically," Outwater says, "just as you'd analyze blood from a crime scene." If the expected reverse complement of the DNA adheres to the marker, the PCR instrument fluoresces a figurative thumbs-up.

Outwater's firm is developing a portable reader, a convenience that other companies already offer. Identif's version uses an applicator that looks like a felt-tip marker. The applicator holds a water-based solution containing the DNA marker's reverse complement. After swiping the product's label or tag with the pen, the dampened area is read with a handheld scanner. If the products's unique nucleic acid sequence is present, a fluorescent signal too weak to be seen by the unaided eye is detected by the scanner and lasts about 30 minutes.

Some handheld readers from Applied DNA probe the DNA marker's structure, but not all do. Some "just verify that the marker is present" by reading a similar optical tag, Hunter explains. The firm also plans to offer backpack-size portable readers, some of which can instantly spot key signatures of the marker's unique identity and others that will verify the DNA's entire structure in about 20 minutes. If deeper probing is needed, the merchandise in question is sent to a high-security lab that offers a verdict within 24 hours.

Such elaborate service isn't expensive, perhaps a few dollars each for a run of a few thousand items such as designer dresses to less than a penny apiece for mass-produced items such as car parts or sneakers.

The DNA markers even could be embedded in drugs themselves. DNA security firms apply their tags to labels on drug boxes or bottles, but Applied DNA is working to convince the FDA that its plant-based markers can be mixed into pharmaceuticals and ingested without harm. Says Julia Hunter, "Being able to tag the medicine itself is the absolute guarantee of security."



DNA authentication isn't limited to brand names. A few celebrities and artists have had their personal DNA incorporated into their signatures on limited-edition books or artworks as a marketing gimmick. But the practice is rare. "There are ethical issues surrounding that question as well as practical ones," says Bancroft, pointing out that distributing an individual's DNA could be an invitation to forms of mischief currently unimaginable. "There are still paternity suits pending against Elvis Presley's estate," one observer notes. "What might happen if pieces of a person's genome are in public circulation?"

Still, it might be only a matter of time until an airport screener or corporate security guard asks to swab your cheek or scrape your skin to check your identity against a DNA sample filed in a database. "It'll be years before a customs official can have you put your finger in a DNA reader and make sure that your DNA belongs to the person you claim to be," Hunter says. "But potentially it's doable."

According to Outwater, "It's too expensive now, but probably not 10 or 20 years from now. There will have to be some breakthroughs in amplifying and reading DNA faster, but at today's pace it might not be far off." No doubt someone is at work on the problem. "Whether for identifying products or people, he says, "DNA is the ultimate identity guarantee."

Bennett Daviss daviss@sover.net is a freelance writer in Walpole, NH.


DNA can hide information as successfully as reveal it. Carter Bancroft, a professor of physiology and biophysics at the Mount Sinai School of Medicine in New York City, and his colleague Catherine Clelland, imagine hiding DNA messages in microdots, a staple information-smuggling device of 20th-century spies.

To encode a message, you simply assign each letter of the alphabet a string of DNA bases: B = CGA, F = TTG, and so on. Next, you stitch together a sequence that spells out the message, flank it with a pair of primer sequences, and hide the message in a mass of DNA. You then bury the whole DNA mixture in a microdot not much bigger than the period at the end of this sentence. Armed with the primer sequences and the substitution code, the message's recipient can use standard techniques to amplify the genetic material, locate the primer sequences, and read the message between them.

Bancroft says such ciphers are ironclad: "You'd have to do 1020 PCR reactions to randomly hit upon the right combination of primer sequences to locate the message." But John Reif, a professor of computer science at Duke University, has argued mathematically that a sophisticated code-hacker can locate messages hidden between primer sequences even without knowing what the sequences are. So Reif has gone Bancroft one better and devised a DNA-based code system that has proven mathematically to be unbreakable.

Reif's method first translates a computer message, encoded as binary digits, into short sequences of DNA bases, something that researchers in biomolecular computing have already done. Using standard DNA synthesis techniques such as photolithography, code-makers then lay out that message in as many as a million distinct DNA sequences on a silicon chip. Recombinant DNA methods would map each sequence on the chip to corresponding "encoding DNA strands" known only to the message's sender and recipient. By later applying the same laboratory processes, the recipient could map the encoded sequences back to the sequences first laid out on the chip and then decipher the message.

The technique is based on the use of so-called one-time pads, code keys that are discarded and replaced after a single use and therefore theoretically can't be cracked. The problem with one-time pads is that the pad needs to be as big as the message. But DNA can be compacted so effectively, especially when dehydrated, that covertly slipping the pad to the person who must later decode the message becomes far less of a problem.

"These techniques aren't unusual in the world of biochemistry," Reif says, "and these methods of cryptography are well-known and very secure. Our group is just combining well-known techniques from two different fields."

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