From genetic code to security code
Jun 10th 2004
From The Economist print edition
Security technology: Tiny DNA fragments can function as invisible embedded security tags
IT HARDLY needs saying that the double helix of deoxyribonucleic acid—better known as DNA—is one of nature's most wondrous materials. Its twisting strands securely encode the genetic information on which all life depends. But Jun-Jei Sheu, a Taiwanese scientist, thinks DNA might be able to keep other things safe, too.
In the mid-1990s, he had the idea of using microscopic fragments of DNA, embedded like tiny bar-codes into everyday objects, as a security and anti-counterfeiting tool. The mathematical possibilities offered by DNA's long and apparently random sequences of four amino-acid “base pairs” mean that even the humble potato—one of Dr Sheu's initial sources for DNA sequences—offers a huge number of variations. “It's almost like God's own algorithm,” says Rob Hutchison, boss of Applied DNA Sciences, the Los Angeles-based biotech company that now markets Dr Sheu's technology outside Asia.
The main scientific obstacle was that “naked” DNA is actually quite delicate. Exposure to ultraviolet light, for example, can damage it within hours. By 2001, however, Dr Sheu had created a substance that can, he says, protect DNA for a century or more. The exact specifications of this “protective envelope” remain secret. But it means that fragments of plant-derived DNA, typically between 1m and 10m base-pairs long and specially manufactured for each application, can be added to almost anything.
It can, for example, be mixed into the ink or paper that is used to make passports or currency. It can be embedded into product labels, or sprayed on to cotton to mark its country of origin. DNA fragments can be embedded in the plastic containers used to hold pharmaceuticals or suspended in expensive fluids, such as perfumes, to prove they are the genuine article.
Secure DNA fragments can even be ingested safely, says Mr Hutchison. The manufacturer of a fancy rice-wine in Asia now mixes DNA fragments into its product and provides buyers with a simple detection kit that allows them to prove their bottle's legitimacy. In America, the approval process for ingestible DNA fragments is now under way. Once approved, they could be embedded both in the inks used on prescription bottles, and the pills inside, to confirm they are genuine.
All of this, of course, depends on being able to detect the presence of a DNA fragment reliably. The simplest technique involves a pen-like device that causes a colour change in ink that contains the DNA fragments. This test demonstrates that DNA fragments are present, but does not reveal anything about their particular genetic sequence. A more rigorous test uses a scanning device about the size of a suitcase. Using technology borrowed from the field of DNA fingerprinting, it can confirm that an embedded DNA fragment matches a reference fragment within ten minutes. A third, more complicated test done in a forensic laboratory can provide an even greater level of certainty for use in court proceedings.
Applied DNA Sciences has also devised a way to incorporate DNA fragments into the chips on smart cards. When the card is inserted into a reader, the chip checks that the fragments are present and undamaged, and if so returns an identification code. This approach can be used to make pass keys to secure areas that are almost impossible to duplicate, the company claims. The idea that DNA encodes your identity has, it seems, been given a new twist.
