Sensor identifies trace samples of cells and proteins in minutes

30 April

Philadelphia, USA. A biosensor that can detect cells and proteins in trace samples and in only minutes has been developed by a a Drexel University engineering professor.

The sensor, which contains a millimeter-size cantilever, could have wide applications in medical diagnostic testing (eg prostate cancer, detecting contamination in food products (eg E. coli bacteria) and monitoring for biothreat agents (eg 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 handheld sensor, developed by Dr. Raj Mutharasan over the past six years, can yield findings in about 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. The article may be found at http://pubs.acs.org.

Results of a preliminary study using the device to detect noninvasively a prostate cancer biomarker in 15 minutes were recently presented at the 96th annual meeting of the United States and Canadian Academy of Pathology.

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.

Mutharasan recently expanded the sensor’s applications to food toxins and biomarkers. A commercial prototype of the sensor is anticipated to be completed in July. Mutharasan is working with a company that has licensed Drexel’s technology to commercialize the device and expects it to be in the hands of food-safety experts soon.

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