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Implanted Sensor Monitors Alcohol in Body

Alcohol monitoring chip

Alcohol monitoring chip (David Baillot, UC San Diego Jacobs School of Engineering)

11 April 2018. A university bioengineering lab developed a tiny implantable sensor that in lab tests tracked alcohol levels in bodily fluids, while requiring little power, making it capable of operating for extended periods. The development team from University of California in San Diego described the device in yesterday’s sessions of the IEEE Custom Integrated Circuits Conference in San Diego.

Researchers from the Biosensors and Bioelectronics Group at UC-San Diego, led by engineering professor Drew Hall, is seeking unobtrusive methods for easily monitoring alcohol levels in people needing help in dealing with alcohol abuse. Centers for Disease Control and Prevention says excessive alcohol use, either heavy or binge drinking, is associated with increased risk of liver disease and unintentional injuries, among other disorders. The National Survey on Drug Use and Health in 2015, cited by the IEEE paper’s authors, notes that 27 percent of adults in the U.S. engaged in binge drinking, while 7 percent reported heavy alcohol use. The survey also shows about 15 million adults suffer from alcohol use disorder.

Treating alcohol abuse often requires close monitoring of alcohol consumption to prevent relapse, but Hall and colleagues point out that most tools for this purpose have drawbacks. Breathalyzers are bulky and require individuals to initiate their use, while blood tests can be taken only by clinicians. Newer methods, such as tattoo-style electronics worn on the skin address some of those issues, but they can be removed or are designed to be used only one time.

“The ultimate goal of this work,” says Hall in a university statement, “is to develop a routine, unobtrusive alcohol and drug monitoring device for patients in substance abuse treatment programs.” The lab’s solution is a device they call the BioMote, a chip device measuring 1 cubic millimeter, and designed to be implanted under the skin. In that position, the chip interacts with interstitial fluids, which are a thin fluid layer surrounding cells, and make up about 40 percent of the water in the body. Alcohol levels in interstitial fluids correlate directly with alcohol in the blood.

The chip contains three gold and silver circuits, one with a coating of alcohol oxidase, an enzyme that reacts with alcohol resulting in a measurable electrical signal. The other two sensors measure pH levels and background noise. The team designed the chip as a potentiostat, a device with working and reference electrodes that measures current flow between those two electrodes. This design makes it possible to measure signals from the alcohol sensor, while canceling out pH and background signals that would otherwise corrupt the alcohol sensing signal.

A key objective of the BioMote is to use as little power as possible. The researchers were able to construct the device to use only 970 nanowatts, which the team says is about 1 millionth the power used in a typical smartphone voice call. The BioMote achieves this low power draw by off-loading the power source to a wearable device, such as a smartwatch or fitness band, paired with the sensor chip. BioMote draws power from the close proximity of the wearable system, which also receives data from the chip. The device uses a backscatter method, where the wearable system sends radio-frequency signals to the implanted chip, which are reflected back to the wearable system that interprets patterns in the reflected signals to calculate alcohol levels.

The researchers tested the BioMote’s concept in the lab using skin tissue from pigs. In the tests, the team sent varying levels of ethanol through the tissue samples, which the chip accurately detected and measured.  “We’ve shown that this chip can work for alcohol,” notes Hall, “but we envision creating others that can detect different substances of abuse and injecting a customized cocktail of them into a patient to provide long-term, personalized medical monitoring.”

The university filed a provisional patent — a document noting an intent to file a regular patent — on the technology, and the lab is working with start-up company CARI Therapeutics, incubating on the UC-San Diego campus, to commercialize the BioMote for alcohol and other substance abuses.

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