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A novel sensor to detect bacterial contamination in food and water

  • Figure showing E.coli cells binding to the sensor

Figure showing E.coli cells binding to the sensor.

A group of scientists at IISc have successfully designed a sensor to detect the presence of harmful bacterium Escherichia coli in food and drinking water. 

Escherichia coli(E. coli) is a bacterium that causes gastrointestinal diseases like bloody diarrhea. E. coli enters the human body through the intake of contaminated food and releases toxins that damage cells of the liver and kidney. In extreme cases E. coli infection can lead to kidney damage. This first-of-its-kind sensor can help identify food and water contamination rapidly and very accurately.

Developed by Dr. Sai Siva Gorthi’s and Prof. Sundarrajan Asokan’s research teams at the Department of Instrumentation and Applied Physics and Robert Bosch Centre for Cyber Physical Systems, IISc, this sensor efficiently detects the presence of E. coli in food and water samples. Its working is rather simple: you add the sample solution to the surface of the sensor. The E. coli cells from the sample bind to the sensor.

Though the fabrication process is relatively easy, the design requires a working knowledge of optical fiber technology, immunology and cell biology.  Cells of bacteria have proteins that can specifically be recognized by certain molecules called antibodies.Antibodies are fixed on the surface of the sensor. When the E. coli come in contact with the antibodies, they specifically bind to it.

This sensor is made using a photo-sensitive optical fiber and is called a ‘bare Fiber Bragg grating (bFBG) sensor’, which is coated with antibodies specific to E. coli. When a beam of light comprising of a band of wavelengths is passed through the bFBG sensor, it reflects one particular wavelength of light.  When exposed to a sample in which E. coli cells are present, the E. coli cells bind specifically to the sensor. This causes a shift in the reflected wavelength which is detected sensitively.

Conventionally, detection is carried out through a tedious process called ELISA (Enzyme Linked Immunosorbent Assay), which consumes more time and requires skilled personnel. Also, there is a chance of inaccuracy due to a change in the sample during storage.

The most exciting moment during the study was “to see the sensor respond to the E. coli present in the water sample”, said Rajesh Srinivasan and Sharath Umesh, students at     Dr. Gorthi and Prof. Asokan’s lab, respectively.

About the Study

A provisional Indian patent has been filed for the detection technology.

Indian Patent:  Application No 6275/CHE/2015.

About the Team

Sai Siva Gorthi, an Assistant Professor at the Department of Instrumentation and Applied Physics, IISc. saisiva.gorthi@gmail.com

Sundarrajan Asokan, a Professor at the Department of Instrumentation and Applied Physics, and Robert Bosch Centre for Cyber Physical Systems, IISc. sundarrajan.asokan@gmail.com

Rajesh Srinivasan, a PhD student at the Gorthi Laboratory at the Department of Instrumentation and Applied Physics, IISc.

Sharath Umesh, a PhD student at Prof. Asokan’s Laboratory at The Department of Instrumentation and Applied Physics, IISc.

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