The Microbe Hunter

DailyTechInfo based on ECN materials: Engineer develops real-time listeria biosensor prototype 

Specialists of AgriLife Research, a subsidiary of Texas A&M University, and their colleagues from the University of Florida have developed a new type of bio-sensor that can detect the presence of listeria bacteria in the analyzed samples. At the same time, the sensor detects very small concentrations of bacterial infection and does it within two to three minutes, practically in real time.

"In the very near future, we will bring the sensitivity of our sensor to such a level that it will be able to detect single bacteria in a sample of material weighing 25 grams," says Dr. Carmen Gomes, lead researcher at AgriLife Research, "In addition, exactly the same technology can be used to detect other pathogenic organisms, for example, E. coli. But listeria was chosen as a starting point because of their ability to survive even at very low temperatures. This is one of the most common types of microorganisms affecting food products, and the cause of a third of deaths from food poisoning."

Currently, the detection of pathogenic bacteria of the listeria species in food products requires the work of highly qualified personnel working in specially equipped laboratories. And the processes of detecting bacteria themselves can go on for several days. Therefore, it often happens that due to the lack of express analysis methods, products infected with listeria enter the consumer market.

The bio-sensor created by scientists is still under experimental development, but a ready-made portable device based on it may appear in the very near future. And the most attractive thing about this case is that even people with the lowest level of qualifications will be able to use such a device.

Despite its nondescript appearance, the sensor is a very complex device consisting of a base, electrodes, and a nanostructured surface on which active biological components capable of reacting to bacteria of a certain type are located. These biological components are elements of single-stranded DNA or RNA molecules that bind to receptors located on the outside of the cell membrane of a pathogenic microorganism. Such a connection can be compared to how a key of some exotic shape can only enter the keyhole intended for it.

The idea of implementing such a "binding" was borrowed by scientists in wildlife. The prototype was a squid of the species Euprymna scolopes, a marine creature that forms a symbiotic relationship with bioluminescent bacteria using a similar mechanism. 

On the body of the squid there are microscopic "hairs" that select and capture only bacteria of a certain type from the entire variety of microorganisms living in the ocean.

Currently, the created bio-sensor has a size comparable to the size of a postage stamp, only two wires attached to certain places of its core depart from it. Within a few minutes, when the polymer "hairs" on the surface of the sensor capture bacteria of a certain type, the resistance of the sensor changes dramatically, which is quite simply measured by traditional electronic methods.

It should be noted that with some modification, such sensors can be connected to the circuits of smartphones and laptop computers. And the paper disposable bio-sensor currently being developed will be very cheap to produce, it will be easy to get rid of it after using it.

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01.07.2015