A safer and faster way of detecting biological weapons agents has been devised by UK researchers with support from the government’s defence research agency.
The optical sensor, developed at UMIST with the help of the Defence Science and Technology Laboratory, is designed to detect changes in antibodies when they come into contact with samples of deadly bacteria such as anthrax. It can also be used to detect bacteria that can lead to food poisoning.
Existing detection devices based on the use of antibodies tend to have low sensitivity – at least 10 million bacteria cells have to be present in 1ml of sample to produce a detectable signal. But levels as low as 10 cells per millilitre can cause infection, making the devices dangerous to use. The UMIST device can operate with a much smaller sample size, said Dr Mohammed Zourob of the university’s department of instrumentation and analytical science, who developed the sensor with Dr Nicholas Goddard.
The device, known as a waveguide, is based on a coating of antibodies chosen to target specific bacteria, on to which a light source is shone. When the antibodies come into contact with these bacteria they attack them, changing the way the sensor surface reflects and absorbs light and allowing the germs to be identified.
The waveguide uses a wider field of light than existing sensors, so it can detect changes across the whole sample while existing systems can monitor only certain areas of the surface.
Unlike existing systems the device also uses ultrasound to direct the way the suspect bacteria are deposited, concentrating the sample on the surface and helping to speed up detection, while allowing the cell numbers to be kept small, said Zourob.
‘Previously sensors needed 30 minutes [for detection] but our sensor needs two to three minutes or less.’
The device also analyses the reflected light to detect optical scattering effects and fluorescence, which help indicate the type of bacteria present. Existing devices monitor only basic changes in the optical properties of a sensor’s surface, and cannot distinguish between benign and malignant bacteria, leading to false alarms.