This graphic depicts a new ultrasensitive biosensor that could open up new opportunities for early detection of cancer and “personalized medicine” tailored to the specific biochemistry of individual patients. The device, called a Flexure-FET biosensor, could be several hundred times more sensitive than other biosensors. Image: Purdue University |
Researchers have created an ultrasensitive biosensor that
could open up new opportunities for early detection of cancer and
“personalized medicine” tailored to the specific biochemistry of
individual patients.
The device, which could be several hundred times more
sensitive than other biosensors, combines the attributes of two distinctly
different types of sensors, said Muhammad A. Alam, a Purdue University
professor of electrical and computer engineering.
“Individually, both of these types of biosensors have
limited sensitivity, but when you combine the two you get something that is
better than either,” he said.
Findings are detailed in a paper appearing in the Proceedings of the National Academy of
Sciences. The paper was written by Purdue graduate student Ankit Jain, Alam,
and Pradeep R. Nair, a former Purdue doctoral student who is now a faculty
member at the Indian Institute of Technology, Bombay.
The device—called a Flexure-FET biosensor—combines a
mechanical sensor, which identifies a biomolecule based on its mass or size,
with an electrical sensor that identifies molecules based on their electrical
charge. The new sensor detects both charged and uncharged biomolecules,
allowing a broader range of applications than either type of sensor alone.
The sensor has two potential applications: personalized medicine,
in which an inventory of proteins and DNA is recorded for individual patients
to make more precise diagnostics and treatment decisions; and the early
detection of cancer and other diseases.
In early cancer diagnostics, the sensor makes possible the
detection of small quantities of DNA fragments and proteins deformed by cancer
long before the disease is visible through imaging or other methods, Alam said.
The sensor’s mechanical part is a vibrating cantilever, a
sliver of silicon that resembles a tiny diving board. Located under the
cantilever is a transistor, which is the sensor’s electrical part.
In other mechanical biosensors, a laser measures the
vibrating frequency or deflection of the cantilever, which changes depending on
what type of biomolecule lands on the cantilever. Instead of using a laser, the
new sensor uses the transistor to measure the vibration or deflection.
The sensor maximizes sensitivity by putting both the
cantilever and transistor in a “bias.” The cantilever is biased using
an electric field to pull it downward as though with an invisible string.
“This pre-bending increases the sensitivity
significantly,” Jain said.
The transistor is biased by applying a voltage, maximizing
its performance as well.
“You can make the device sensitive to almost any
molecule as long as you configure the sensor properly,” Alam said.
A key innovation is the elimination of a component called
a “reference electrode,” which is required for conventional
electrical biosensors but cannot be miniaturized, limiting practical
applications.
“Eliminating the need for a reference electrode
enables miniaturization and makes it feasible for low-cost, point-of-care
applications in doctors’ offices,” Alam said.
A U.S.
patent application has been filed for the concept.
