Smartphone-compatible device ‘cuts disease test times’ with one drop of blood

(Credit: BernardaSv/ iStock)

(Credit: BernardaSv/ iStock)

A new smartphone-compatible diagnostic tool could slash the time needed for life-saving disease tests, a team of researchers has said.

Biomedical engineers at Duke University in North Carolina said their new device detects disease markers “as accurately as the most sensitive tests on the market” in a fraction of the time. The tool, called the D4 assay, spots low levels of antigens ­– protein markers of diseases – in a single drop of blood.

The team created the D4 by printing antibodies onto a glass slide with a non-stick polymer coating. The coating stops proteins not associated with disease from attaching to the slide, removing “background noise” from results and making the device more sensitive than it would be otherwise. When blood touches the antibodies, they dissolve and bind to target proteins and create fluorescent light to reveal how much of an antigen is present.

Users then read results using a table-top scanner or a 3D-printed smartphone attachment. The Duke team said their “lab-on-a-chip” identifies disease biomarkers in as little as 15 minutes – far quicker than the current “gold standard” enzyme-linked immunosorbent assay (Elisa) test. Elisa detects diseases like Zika or HIV, but requires trained researchers or liquid-handling robotic devices.

“What’s cool is that our assay can achieve comparable sensitivity to the Elisa within 15 minutes, and if further sensitivity is needed, longer incubation times can be used,” said engineer Daniel Joh from Duke University.  “This device can also be compared to a lateral flow test, which is quite fast as it takes less than five minutes to get a reading, but that test isn’t as sensitive. This is really the best of both worlds.”

The researchers used the D4 in clinical trials, measuring levels of serum leptin – a hormone which can reveal mortality and complications in malnourished children – in patients at Duke University Medical Center. Joh and co-author Angus Hucknall will next use their prototype in a field test in Liberia to better understand how results can monitor and help plan treatment strategies for malnutrition, and how it can perform wider diagnostics.

The device offers efficient and accessible testing which could be useful in remote or developing parts of the world, the team said. They said D4 chips will cost less than $1 and the smartphone attachment developed at the University of California will be less than $30.

“Diagnostic tools such as this have significant advantage over existing lab-based methods in that they can be used in the most extreme and isolated of areas, enabling communities who previously would have had to travel for days to a hospital to be tested in their own home or at a local clinic,” said Dr Helen Meese, head of healthcare at IMechE, to Professional Engineering. “This type of equipment means that clinicians can sample, analyse and diagnose patients more rapidly with equivalent or better results than existing techniques.”

Many more “lab-on-a-chip” devices will be developed in the coming years, she added, as they shrink from desk-sized to handheld and even plug-ins for mobile devices. However, as with other medical technology they face extensive research and clinical trials before widespread introduction.

The research was published in the Proceedings of the National Academy of Sciences.

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