Predicting Illness

Disease Diagnosis by Chip

Am I Getting Sick?,   By R. Colin Johnson

Commissioned by CACM Staff, July 14, 2022

A microfluidic chip for diagnosing diseases, which uses a minimal number of components and can be powered wirelessly by a smartphone.

Credit: Laboratory of Nanostructures and Biosensing, University of Minnesota

The future of "at-home" medical diagnostics went viral recently when the government started giving out free Covid tests.

People have been familiar with at-home medical testing for more than 50 years; the first patent for an in-home pregnancy test was filed in 1969.

Experts like Boston University professor Kenneth Burch say that what people really want from such in-home tests is not to just know what they already suspect (such as whether they are pregnant after missing a menstrual cycle), but to know the root cause of ambiguous symptoms. Are your sniffles just the result of a high pollen-count day and nothing worth worrying about, or are they an early sign of something more serious, ranging from a common cold to influenza to a weaponized laboratory-born virus?

For that reason, experts like Burch believe the future of over-the-counter at-home medical tests is trending toward multiple-malady detection—the first of which will likely be debuting as soon as next year (from Johnson and Johnson).

"I suspect a wider range of single-malady tests are unlikely. More likely are devices that are multiplexed—in other words, which can detect multiple targets—for example, the eight most common causes of your symptoms," said Burch.

Burch has been working in this field for many years, and has become a sought-after advisor on the capabilities of state-of-the-art medical electronics. According to Burch, the technology for eight simultaneous tests has just become the state of the art of what is possible for medical diagnostics whose goal is not to cure, but to aim people with very early symptoms to the correct medical specialist. Labs already prototyping multi-malady at-home tests range from government-funded bioweapon experts like the Biomedical Advanced Research and Development Authority (BARDA, a part of the U.S. Department of Health and Human Services) to giant consumer labs like Johnson and Johnson Innovation (JLABS), as well as independent at-home testing startups such as GRIP (Graphene Rapid Identification Platform) Molecular Technologies Inc.

The key to the technology underlying at-home simultaneous testing for multiple potential ailments is graphene—the pure crystalline lattice form of carbon, the building block of biology. Once thought to be a successor to silicon chips, graphene chips may have found a more suitable application in at-home medical testing, because graphene is the ultimate in bio-compatibility (since we are carbon-based life forms). Graphene also can function in field-effect transistors (FETs), which already are used in many type of medical devices.

In particular, G-FETs behave in the same manner as the silicon FETs that enable electronics with which we are already familiar, from mainframes to smartphones to pacemakers to defibrillators. They also smoothly interface with human "analytes"—the bodily fluids that can indicate the presence of a specific malady. A single atomic layer of graphene—used as the channel of a G-FET—can identify the presence of any known human analyte, thus detecting nearly any type of disease, according to the experts.

"G-FETs are appealing for developing diagnostics due to their ease of functionalization, electrical readout, robustness and ultrahigh sensitivity to numerous biological analytes," said Burch. "One simply stacks a 'linker' molecule on the graphene, then attaches any of a wide variety of biological molecules that bond with specific analytes."

The National Institute of Health (NIH) is developing such devices to identify rare diseases, blood disorders, and chronic obstructive pulmonary diseases. Independent labs have developed other devices for at-home medical testing, such as the Digital Dipstick for instantly identifying bacteria infections, and the Flow Cytometer for quickly pinpointing the severity of HIV infections.   ... '