Fiber-optic sensor identifies E. coli bacteria in less than 20 minutes

A new fiber-optic sensor can detect potentially deadly E. coli bacteria over a wide temperature range, and in 15–20 minutes.

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Researchers from the Photonics Research Center at the University of Quebec (Outaouais, QC, Canada; led by Professor Wojtek J. Bock) and collaborators from the Indian Institute of Technology Kanpur (India) have developed a fiber-optic sensor that can detect potentially deadly Escherichia coli (E. coli) bacteria over a wide temperature range, and in 15–20 min rather than several hours to days.

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The new sensor uses bacteriophages (viruses that can naturally latch onto and kill bacteria), which are bonded to the surface of an optical fiber to "grab" E. coli bacteria from a sample and keep them attached. When a beam of light strikes the surface, the presence of E. coli shifts the wavelength in a telltale sign of bacterial contamination.

A packaged fiber-optic sensor showing an inlet and outlet for the bacteria-tested water. (Credit: Courtesy of Dr. Wojtek J. Bock/Photonics Research Center, University of Quebec, Outaouais, Canada)

One of the challenges of using optical fibers for bacteria detection is that temperature changes can alter the optical properties of the materials. Sensors are therefore often designed to work at a particular temperature and give inaccurate readings if the sample gets much hotter or colder. But Saurabh Mani Tripathi, a physicist at the Indian Institute of Technology Kanpur, and his colleagues overcame this challenge by adding an additional optical component and in effect canceled out temperature-induced shifts. Their device is temperature-insensitive over an approximately 68°F range, starting at room temperature and going up to 104°F.

The temperature insensitivity makes the sensor more practical for outdoor applications, like onsite monitoring of water reservoirs, Tripathi says. He also noted that the food industry and pathology labs are other possible users of the new sensor, which can be modified to detect other strains of bacteria by changing the bacteriophage.

The research group is currently collaborating with Security and Protection International (Ottawa, ON, Canada) to explore commercialization of their device. Bock says that costs are hard to estimate at this stage of the research, but that the team hopes to deliver portable units for a few thousand dollars.

Full details of the work appear in the journal Optics Letters; for more information, please visit http://dx.doi.org/10.1364/ol.41.004198.

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