Science and technology is playing a big part in combating terrorism. Ian Farrell looks at how analytical science is helping.

Science and technology is playing a big part in combating terrorism. Ian Farrell looks at how analytical science is helping.

On 11 September 2001, four planes were hijacked and used to attack targets in the US, close to 3000 people were killed and the world changed forever.

This represented only the second time that the US had been attacked on it own soil by a foreign power; the first being the strike on Pearl Harbour by the Japanese in 1941. Countries in Europe and Asia have dealt with terrorism on home soil before, but for the US this was a new phenomenon. The thousands killed on 9/11 represented the US’s wake-up call: a nation that widely perceived itself to be invincible now felt vulnerable.

Not long afterwards came numerous letters containing anthrax in the US postal system, and with them the realisation that terrorists didn’t only have to rely on explosives and guns. All kinds of possibilities were raised: biological attacks using agents like anthrax, plague or botulism; chemical weapons, such as the deadly nerve gas Sarin which killed 12 people and affected more than 5500 others on the Tokyo subway in Japan in 1995; or even the millions of tonnes of toxic industrial chemicals (TICs) that are part of the US’s multi-billion dollar a year manufacturing industry. Here were new and frightening weapons that needed new ways to detect and stop them.

The US public was genuinely scared. They didn’t know what to expect next, or how to protect themselves. The government had to do something to protect its citizens and, more importantly, had to be seen to be doing something to win back public confidence.

Enter the two things that the US has that its disparate foe does not: science and money. The US has always invested heavily in military science and technology, but with more of an aim to using it on the battlefield. Since 2001, however, investment in research specifically aimed at homeland security has increased massively. In 2004, the US government’s Department of Homeland Security had a budget of $36.5bn (?20.1bn), which is expected to rise to $40.2bn in 2005. Part of the department’s role is to coordinate research into new ways to detect, prevent and deal with terrorist threats.

’The Department of Homeland Security doesn’t do any real research itself,’ explains Stuart Cram, director of homeland security for instrument manufacturer Agilent Technologies. ’What it does do is collect information from various sources and bring it together, publishing warnings and information of its own. It also funds other government agencies to do research - the FBI, CIA, Environmental Protection Agency etc.’

Agilent is one of a number of scientific companies that have done well out of the US’s growing need for security against terrorism, but Cram maintains that, for his company, this is nothing new. ’We started the programme in homeland security right after 9/11, but this isn’t a new business for us. We’ve been working in this field for years, in conjunction with the military, making detection equipment for chemical and biological warfare agents.’ He explains that this came about as a result of the SALT II treaty on the limitation of strategic offensive arms signed by the US and Soviet Union in 1976. ’If you are going to destroy these things [chemical and biological weapons], you have to do it extremely carefully. Where are you going to do it? How are you going to do it without contaminating the environment? You have to think about the consequences of accidents and what could happen if they get into the population somewhere, because these things can travel for hundreds of miles. It’s a very challenging problem,’ says Cram.

After 9/11, he says Agilent realised that the problem was a little different. New hazards were involved, like anthrax. ’We looked at what we already had and what was in the pipeline and went out to address this market.’

Agilent’s most recent commercial success has been the development of laboratories that can operate in a variety of conditions and be deployed at a moment’s notice. If it is physically not possible to bring a specimen to a permanent lab, packing crates housing chromatography, mass spectrometry and bio-analyser equipment can be dropped from a transport plane and be ready to go in a very short time.

More recently, Cram’s department has produced what he calls a lab on wheels. ’There is a lot of interest in making these kinds of measurements in the field using mobile laboratories, because they are easy to drive. It’s not like a big truck,’ he explains.

Inside, the lab has gas chromatographs and mass spectrometers that are designed specifically to look for chemical warfare agents, and set-ups that are geared towards detecting TICs and explosives. There are also separate chromatography systems that look for biological agents, most of which are liquids. The samples come in at the back of the vehicle through a glove box and sealed container. It is computer automated with safety interlocks to protect the people working inside from accidental exposure. ’It’s a Class III glove box,’ says Cram, ’which means you can handle things that are biologically active to a level that, if adult humans were exposed to them then their expected lifetimes would be measured in minutes. And that’s exposure to microgram quantities.’.

Biological agents are much more difficult to identify by simple lab measurements than chemical compounds. A quick lab test may be able to confirm that a sick person has a bacterial infection, but that’s about where it ends. To get any more information scientists have to turn to genomics.

Genotyping a bacterium is a more complicated affair and requires specialist lab equipment. The process can take hours, during which time the patient must wait and an infectious agent could be transmitted over a huge area. Richard Mathies of the University of Berkley, US, is using nanotechnology to speed-up the process and hopes to take gene sequencing into the field. Using microfluidic channels in glass wafers, he has developed a method of carrying out polymerase chain reaction (PCR) on volumes in the order of tens of nanolitres. This is followed by small-scale separation by capillary electrophoresis.

’We have completely integrated sample preparation onto the chip, which required some really fundamental development work,’ he explains. ’We have made very small valves from polydimethylsiloxane that, from a conceptual point of view, are a huge leap forward. Imagine electrical devices like amplifiers and logic gates. At the end of the day these are just made of transistors. In the same way we can group these new valves together and make devices like pumps, routers, mixers and storage reservoirs - a true lab on a chip.’

Mathies has integrated heaters and temperature sensors onto the chip giving him very fast thermal response times: ’thermal cycling is so good that we get tremendous sensitivity. Traditionally biologists use gels, trans-illuminators and ethidium bromide that is quite crude and insensitive really. They over amplify during PCR to get enough signal and in doing so introduce a ton of noise. Our method uses fewer cycles and gets very clean results. We can do a complete PCR cycle in 30 seconds. The whole genotyping process only takes 10 minutes.’

Mathies’ chips ’plug’ into a machine dubbed ’Gataca to go’ - a portable collection of power supplies, fluid pumps, lasers and detectors that is about the size of a shoebox. The idea is that this can be used in the field rapidly to genotype and identify bacteria when shipping samples to a lab is impractical.

But Mathies sees uses for the technology beyond homeland security. ’The idea of developing something that is just a [chemical and biological weapons] detector is not what I want to do. There has been a need for better disease diagnosis in the public health arena for years, but the funding hasn’t been there to develop it,’ he says. Mathies would like to see a machine in every emergency room and doctors’ office in the US. ’When someone comes in who is sick, rather than say "yes, you have a bacterial infection" and prescribe broadband antibiotics, we could tell exactly which bacterium is causing the problem, and even tell whether it is resistant to antibiotics or has been artificially engineered. Economically we are running out of antibiotics and we can’t just go on developing more and more.’

He explains that the money to develop these technologies, both at the research and commercial levels, is miniscule and that the research field has been stagnant for decades. ’Concerns over chemical and biological weapons are very important, but they also provide an opportunity to develop technologies that are dual-use,’ he says.

As yet, an attack on the US using chemical, biological or radiological weapons remains a hypothetical scenario - albeit a chilling one.

Almost all terrorist attacks rely on explosives or guns, and detecting these is still the most important way of preventing hijackings, hostage situations or suicide bombings. Metal-detectors can tell if a suspect is carrying a gun on his or her body, and x-rays are effective at screening baggage, but it is still difficult to see if materials like plastic explosives, toxic agents or illicit drugs are hidden on the body.

If you travel regularly by air, however, you may have seen one way in which analytical science is helping to tackle this problem. It is not uncommon for airport passengers to be pulled over at a security screening and have a guard search through their hand baggage with a plastic stick tipped with a piece of absorbent paper. The absorbent paper gets dropped into an anonymous looking box and, hopefully, the passenger is told they can go on their way.

What has just happened is a clever piece of chemical analysis. By swabbing the baggage or clothing of a passenger, a security guard is trying to pick up any traces of explosives or narcotics and analyse for them in an ion-mobility spectrometer.

Ion-mobility spectrometry (IMS), unlike traditional mass spectrometry, operates at atmospheric pressure so does not require a bulky high-vacuum pump.

The sample, in this case a swab that his been run over a passenger’s clothing and baggage, is put into a small oven which heats any volatile substances present and allows them to be swept into the main part of the instrument. Here the sample, along with a carrier gas, is bombarded with electrons from a radioactive source and is ionised. The ionised gas then moves through an electrical field inside a ’drift tube’. Large ions collide more often than smaller ones and so are delayed by several seconds on their way to a detector.

The amount of chemical information obtained from IMS is nowhere near as detailed as that gained from a traditional mass spectrometer, but where the technique comes into its own is in comparing the drift times of a sample against a database of known compounds. When a sample recognises a signature, a person or piece of baggage can be checked more thoroughly.

In less than 10 seconds, IMS can screen for explosives, including TNT and Semtex, and drugs such as cocaine, heroine, LSD, ecstasy and marijuana. Picogram detection levels are achievable and a high degree of automation means the machine can be operated with minimal training.

A recent development, marketed by Smiths Detection, is a walk-through explosives detector known as the Sentinel. A non-threatening computerised male voice asks a person to ’walk forward’, ’turn right’, etc, while gentle puffs of air are blown across them. The idea is that any traces of volatile explosives will be blown towards IMS detectors on the opposite wall of the structure. The device, one of which has been installed at the recently re-opened statue of liberty, can screen and record 420 people per hour.

A scanning technology called terahertz imaging is also under development. Terahertz (THz) radiation occupies a much overlooked part of the electromagnetic spectrum: the region between microwave and infrared. Traditionally, such radiation has been used to probe rotational fine structure in gas-phase spectroscopy, but recently scientists have discovered another use for it. ’It’s a bit like radar,’ says Mike Kemp, vice president of business development security at TeraView, a company that is developing security screening devices based on THz spectroscopy at its research facility in Cambridge, UK.

Broadband femtosecond pulses of THz radiation are fired at a sample and the time-of-flight of the reflections that come back is measured. As most materials are only partially reflective towards THz rays, some of the beam is bounced back and detected while the rest is allowed to pass through to the next layer of the sample, where another partial reflection is produced, and so on. This penetrative quality means depth profiling can be carried out, and by using mirrors and lenses to scan the beam of pulses back and forth across the sample, a three-dimensional image can be built up.

But THz technology can do more than just image. Some of the rays are absorbed by solid samples, meaning that each material has a characteristic signature spectrum that can be used to identify it. A terahertz imaging scanner can compare the spectrum of the reflections it sees against a database of known samples and alert an operator to the presence of any dangerous substances, like plastic explosives or illegal narcotics. Kemp hopes to see hand-held wand-like THz scanners on the market in as little as two years. ’Crucially, THz rays are safe for humans,’ he adds. ’They occupy a position between the signals used by mobile phones and the IR radiation sent out by a remote control. And the power needed is very low.’

As with Mathies’ Gataca device, THz imaging also has a role to play outside homeland security. Its ability to characterise materials accurately has aroused the interest of pharmaceutical companies that are impressed the technology can distinguish between different isomorphs of the same compound, that may just have crystallised differently in the manufacturing process.

The next time you are stuck at an airport for security reasons or in a queue to have your baggage screened think about what is going on around you and the part that science is playing in keeping us safe. Technology has always been on the frontline of the battlefield, but now that battlefield is closer to home.


Ian Farrell is a freelance science writer