Sensor identifies trace samples of cells and proteins in minutes
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
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
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.