Researchers Develop Sensor to Test for E. coli in 10 Minutes
August 2, 2007
As the Food and Drug Administration forges a plan to revamp its policy on the safety of imported food (it inspects less than 1 percent), a handheld sensor developed by researchers could help prevent deaths and illnesses caused by food contamination.
A Drexel University professor’s millimeter-size cantilever biosensor can detect cells and proteins in trace samples and in only minutes.
The sensor could have wide applications in detecting contamination in food products (E. coli and listeria bacteria), medical diagnostic testing (prostate cancer) and monitoring for biothreat agents (anthrax). In medical testing, the sensor can be used to analyze the four most widely tested fluids: blood, urine, sputum and spinal fluid.
Existing conventional tests require 24 hours and a trip to a laboratory to boost the concentration of microbes in a sample to produce findings. The accurate, handheld sensor Dr. Raj Mutharasan, a Drexel chemical engineering professor, has developed over the past six years can yield findings in 10 minutes.
No direct test for minute amounts of proteins exists on the market. A study published in the April 1, 2007, issue of Analytical Chemistry using Mutharasan’s sensor detected E. coli in ground beef at some of the lowest concentrations ever reported.
Results of a preliminary study using the device to detect noninvasively a prostate cancer biomarker in 15 minutes were recently presented by David Maraldo, a Drexel doctoral student in chemical engineering who worked with Mutharasan on the sensor, at the 96th annual meeting of the United States and Canadian Academy of Pathology.
Kishan Rijal, a Drexel doctoral student in chemical engineering, and Gossett Campbell, who received his doctoral degree in chemical engineering from Drexel in 2006, helped develop the sensor. Dr. Fernando U. Garcia, professor of pathology in the Drexel University College of Medicine, provided urine specimens to Mutharasan in testing for prostate cancer.
The sensor features a vibrating cantilever, supported at one end and coated with antibodies. The antibodies are specific to the desired target such as E. coli, anthrax or proteins that are biomarkers for diseases such as prostate cancer. When the target is present in a sample flowing past the sensor, it binds to the cantilever and changes the frequency of vibration so it can be read electronically.
The sensor affixed with antibodies against E. coli can detect as low as four cells per milliliter of solution. A voltage is applied to the ceramic layer, causing it to expand and contract, vibrating the glass sliver. The sensor detects changes in the glass sliver’s resonance frequency (the point where vibration is the greatest) and determines the presence and concentration of E. coli bacteria.
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