Tiny devices developed for pathogen detection

By Ahmed ElAmin

- Last updated on GMT

Related tags: Bacteria

Scientists in Denmark have created two tiny devices, which they
have leveraged to detect a range of contaminants, from molecules to
whole bacteria, in food and water.

The devices -- one of which uses nano-sized cantilevers, the other coloured markers -- are described in the August issue of Microbiology Today and were created by a team of scientists at the University of Denmark and led by Anja Boisen. The devices open up new and possibly more accurate methods processors can use to detect pathogens in the plant at a time when industry is under regulatory and consumer pressure to clean up its products. Cantilevers are like miniature diving boards that measure 200 micrometers long and 40 micrometers wide, about half the width of a human hair. Boisen and her team developed two cantilevers, which they then placed in a sensor. A liquid is then passed through the two cantilevers. One is the reference cantilever, which helps to eliminate factors such as temperature changes. The other is coated with a detector layer that binds to the specific pathogen to be detected. When the molecule or microbe that is being looked for binds to its surface, the board bends and its electrical resistance is altered. Detection is achieved by measuring the change in resistance, they stated. In the article Boisen says the devic can be designed to search for specific things. For example, if the organism to be detected is E. coli, the cantilever could be coated in antibodies specific to E. coli cells. Many different molecules or organisms can also be recognized simultaneously, she said. "The sensor can be expanded to contain several cantilevers, each coated with a specific detector molecule,"​ said Boisen. A second sensor also have a flexible board or "lid" but this is placed on top of a tiny box that contains marker molecules. The lid is coated with specific detector molecules that bind to the targeted pathogen. On detection the lid deflects, releasing the coloured marker molecules. The lid is about 1 X1 cm. On detection of a pathogen the molecules produce colour visible to the naked eye. "We use processes where the cantilevers are fabricated by etching a thin silicon wafer three-dimensionally,"​ said Boisen. "The procedure is suitable for mass production and it might be possible to make sensors so cheaply that they can be disposable." ​ Both sensors are extremely sensitive and can measure deflections of just 1 nanometre, so are able to detect the presence of very small molecules, she said. "The lid device could be included in food packaging since it requires no external energy and is cheap to make,"​ she said. "When a food is infected, the control unit in the plastic wrapping becomes coloured. Thus a simple colour indicator can show the quality of the food."

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