• Photo by West Midlands Police

Fast DNA testing at the crime scene

Published as part of Australia and China Science and Technology Week at the Shanghai World Expo 2010.

A portable DNA testing device that avoids the need for analysis in a laboratory could save time and money.

“Normally, DNA samples have to be transported back to the lab and need trained people using expensive instruments to conduct the analysis,” says Dr Danny Wong from Macquarie University who is collaborating with biosensor expert Professor Huangxian Ju at Nanjing University, Jiangsu Province, to develop the technology.

“We are developing a portable biosensor that anyone can use to conduct these analyses within minutes,” Dr Wong says.

The sensor detects DNA hybridisation, the process where two single strands of DNA bind to each other to form a double strand. The more closely related the two strands of DNA, the more strongly they bind.

One strand, the probe, is immobilised on the surface of an electrode and is exposed to a single strand of unknown DNA, known as the target. If they are closely related, the DNA will bind strongly, or hybridise. A label attached to the target DNA changes the level of current running through the electrode depending on the extent of hybridisation.

“This change in current is so very small, it is incredibly difficult to measure without generating experimental errors,” says Dr Wong. “To overcome this, we have developed a biosensor that gives an amplified signal.”

Not only does this technique have applications in forensic medicine and medical diagnosis, but it will also enable study of the interactions between DNA and viruses and bacteria.