New Stanford immune-system sensor may speed up, slash cost of detecting disease
BY ERIN DIGITALE
 MARCH 7, 2012 - An
inexpensive new medical sensor has the potential to simplify the diagnosis of diseases ranging from life-threatening immune deficiencies to
the common cold, according to its inventors at the Stanford University School of
Medicine .
Their device, called an integrated microfluidics-waveguide sensor, sorts and counts cells in small samples of blood and
other body fluids. The developers say the sensor provides an easy way to measure different types of white blood cells, a key component
of the immune system. They add that the sensor, which is about the size of an adult's thumbnail, could be deployed in doctors'
offices, newborn nurseries, patients' homes, disaster sites and battlefields.
"A low-cost way of counting cells could provide point-of-care diagnosis and monitoring for immune disorders, allergies,
infections, AIDS, cancer and other disorders," said Manish Butte , MD, PhD,
who led the team of inventors. Butte is an assistant professor of pediatrics at Stanford, a pediatric immunologist
at Lucile Packard Children's Hospital and the senior author
of a paper describing the sensor that appeared online March 7 in Biomicrofluidics . Stanford University
has filed for a patent on the device; the inventors are seeking a partner to commercialize the sensors.
Butte developed the sensor because he wanted a better way to screen newborns for severe combined immunodeficiency, a
congenital illness commonly known as "bubble boy disease" in which infants are born with much of their immune system missing.
The disease affects about one in 100,000 infants. California's current method for screening newborns for this disease takes
three to six weeks to return results, by which time some affected infants could contract life-threatening infections. In
contrast, the new sensor has the potential to detect low T-cell counts, a hallmark of the disease, in a 15-minute test
in the newborn nursery before a new baby goes home from the hospital.
Butte soon realized, however, that the sensor had the potential to aid in diagnosing a wide range of conditions.
The body has many types of white blood cells, each with different disease-fighting roles. White blood cell counts already
help doctors diagnose some diseases and monitor treatment of others, including cancer and AIDS, but current cell-counting methods
require fairly large blood samples and costly, slow equipment that can be operated only by trained laboratory technicians.
One possible application of the new sensor would allow doctors to solve a common, vexing problem: determining the cause of
a runny nose. Instead of using the current trial-and-error method for diagnosing the problem, doctors could take a mucus sample from the
patient in their office and measure the white blood cells present. Elevation of one type of white blood cells could implicate
allergies, another cell type could point to a sinus infection and a third type of elevated cell count could suggest that the
runny nose was simply due to the common cold.
The new sensor consists of a small, rectangular piece of glass impregnated with a strip of potassium ions. The
potassium-impregnated glass acts as a "waveguide" - laser light shone into the strip of glass is transmitted down it in a
specific way, and the light emitted from the far end of the waveguide can be measured with a light sensor.
To operate the detector, a patient's fluid sample is mixed with antibodies specific for the particular type of white
blood cell to be measured. Each antibody is attached to a tiny bead of magnetic iron. Then, the sample is injected in a small
channel on top of the glass waveguide. A magnet under the glass traps the labeled cells in the channel. The iron beads block
a bit of the laser light that would otherwise pass through the waveguide, and this reduced transmission is measured by the
light sensor at the far side of the glass.
The prototype sensor cost about $60 to build using off-the-shelf electronics components, Butte said, adding that
the per-unit cost would be lower if the sensors were manufactured in bulk. In comparison, laboratory machines now used to
count cells cost tens of thousands of dollars.
Butte noted that the sensors could be used by patients as well as by health-care providers.
Catching infections early is important for many patient populations," Butte said, adding that he hopes such
patients - including those who have received organ transplants, suffer chronic kidney failure or are taking
immune-suppressing drugs to treat rheumatoid arthritis - could use the sensors to monitor their immune
systems much in the way that diabetics use glucometers to track their blood sugar at home.
Butte's Stanford collaborators on the project are postdoctoral scholar Daniel Garcia, PhD, and Isaac Ghansah, a biology
undergraduate student.
The research was funded by grants from the SPARK translational
research program at the School of Medicine, the National Institute of Allergy and Infectious Disease , the
Center for Integration of Medicine and Innovative Technology and the Massachusetts Technology Transfer Council.
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Source: Stanford University School of Medicine
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Erin Digitale | Tel (650) 724-9175
digitale@stanford.edu
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Stanford University Medical Center integrates research, medical education and patient care at its three institutions - Stanford University School of Medicine , Stanford Hospital & Clinics and Lucile Packard Children's Hospital . For more information, please visit the Office of Communication & Public Affairs site at http://mednews.stanford.edu/ .
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