Lab on the beat

A portable DNA device that promises to dramatically reduce the amount of time spent analysing crime scenes is expected to begin government Forensic Science Service trials in the next two years.

The system, under development at the University of Southampton, could cut the time it takes to analyse a DNA sample from a couple of days to a couple of hours.

Prof Stephen Haswell, who heads the project at the university’s chemistry department, said that the idea came from earlier work that his department had done into the use of micro-fluidics to analyse chemical compounds.

Micro-fluidics uses miniaturised chips that have a network of microscopic channels etched on to the glass surface. According to Haswell, this process has three unique properties. The first is that the liquid is mixed using a slow diffusion process, and as the sample moves from channel to channel the chemist retains a high degree of control over where and when the chemical reacts.

The chips also have a very high surface-to-volume ratio, which gives the chemist even more control. Crucially, the small volume of liquid in the sample also allows for extremely accurate and efficient temperature control.

Currently a forensic scientist retrieves a sample from a crime scene, but then the DNA it contains has to be amplified so that it can be properly analysed. This involves the use of what is known as polymerase chain reaction (PCR). According to Haswell, this system needs to be streamlined. He estimates that using the new system could increase the efficiency of the analysis by 30 per cent.

‘From a chemist’s point of view PCR is very inefficient,’ said Haswell. ‘Using our micro-fluidic approach we can get very selective and very high-yielding reaction products.’

In PCR, the sample is heated to specific temperatures and the strands of DNA separated out. It can then be replicated, its signal amplified and then detected. Haswell’s technology uses microwaves to heat the material. The liquid absorbs most of the heat, but also loses it very quickly.

Using microwaves in this way could help greatly speed up the amplification process. In existing methods, each amplification cycle takes more than 20 minutes. In tests, the new technology processed each cycle in less than a minute.

Haswell said: ‘This will allow forensic teams to process smaller samples and a greater number of samples more quickly. At the moment samples are put in a bottle, sent to a lab and more often than not it takes a day or two to get a DNA profile back.’

One of the disadvantages of existing systems is that the samples have to be collected and then sent away to a laboratory. The small scale of the micro-fluidic approach means that samples could be tested at the crime scene on a hand-held device. This would not only speed up analysis but also allow for quick profiling before the scene becomes contaminated.

The fact that micro-fluidics uses microwaves to heat and cool the solution also means that, in the future, the portable analyser could be linked to a mobile phone, suggested Haswell. This, he claimed, is of particular interest to the MoD.

One of the biggest challenges will be the integration of all of the analyser’s components, admitted Haswell. ‘Integrating the PCR with the separation, the sampling and the fluorescent detection technology all in one device is quite a challenge, but one which is quite exciting as it will eventually allow for far more applications for DNAbased intelligence,’ he said.

The technology could also be used to test for contaminated food, and individual police officers could carry miniaturised portable analysers for quick use at a crime scene.

Industrial partners on the project include the Centre for Integrated Photonics in Ipswich, which is working on the integration of the optical fluorescent detection components of the device, and Richardson Electronics which supplies the microwave technology.

The project, funded by the EPSRC, runs until 2009, but the Forensic Science Service is expected to begin trialling the technology within the next two years.