Simple Microfluidics Immune System Sensor Developed

Manish Butte (Stanford University)

Researchers at Stanford University School of Medicine have devised a simple, inexpensive sensor to diagnose a range of diseases including immune system disorders. The work of the team led by Stanford pediatrician and immunologist Manish Butte (pictured right) appears today online in the journal Biomicrofluidics; paid subscription required.

The university says it has filed a patent on the technology and is seeking partners to take the sensor to market.

The device is a combination of microfluidics tester that can analyze fluid samples and a waveguide sensor to measure light waves emitting from a laser directed at the test substance. It sorts and counts cells in small samples of blood and other body fluids to provide an easy way to measure different white blood cells, a key component of the immune system.

The many types of white blood cells in the body have different disease-fighting roles. Current methods to count white blood cells for diagnosis and monitoring require fairly large blood samples and costly, slow equipment that can be operated only by trained laboratory technicians.

The new sensor has a small, rectangular piece of glass impregnated with a strip of potassium ions. The potassium-impregnated glass acts as a waveguide, where laser light shone into the strip of glass is transmitted down the glass, and the light emitted from the far end of the waveguide can be measured with a light sensor.

To operate the device, 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 some 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.

Butte developed the sensor to find 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. Current methods for screening newborns for this disease take three to six weeks to return results, by which time some affected infants could contract life-threatening infections.

The new sensor, in contrast, has the potential to detect low T-cell counts in newborns, an indicator of the disease, in a 15-minute test before a new baby goes home from the hospital. The technology can also be applied to the diagnosis of a wide range of conditions. For example, the sensor could analyze a mucus sample from a child with a runny nose and measure the type of white blood cells present in the sample. The sensors would report the number and type of white blood cells, which could indicate conditions such as allergies, sinus infections, or common cold.

Butte says the prototype sensor cost about $60 to build using off-the-shelf electronics components, a cost that would be reduced once produced in large enough quantities. He notes that the sensors could be used by patients as well as by health-care providers.

Read more: Lasers, Electric Fields Aid Lab-on-a-Chip Technology

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