April 12 (UPI) -- A miniature injectable biosensor -- about 1 cubic millimeter in size -- could provide continuous, long-term alcohol monitoring, according to scientists who developed it.
Engineers at the University of California San Diego are developing an ultra-low-power sensor that is implanted in the body just beneath the surface of the skin through a 16-gauge syringe and is powered by a wireless wearable device, such as a smartwatch or patch.
The work was presented this week at the 2018 IEEE Custom Integrated Circuits Conference on in San Diego. The UCSD engineers also have prepared a paper on the device, though it has not yet been published in a peer-reviewed journal.
"The ultimate goal of this work is to develop a routine, unobtrusive alcohol and drug monitoring device for patients in substance abuse treatment programs," project leader Dr. Drew Hall, an electrical engineering professor at the UC San Diego School of Engineering, said in a press release.
Patients in treatment programs are often monitored by Breathalyzers to estimate blood alcohol levels, but they are clunky devices that require patient initiation and are not that accurate, Hall said. Treatment programs also require blood tests, which need to be performed by train technicians.
Another method for monitoring people are tattoo-based alcohol sensors, but they can be easily removed and are only single-use.
"A tiny injectable sensor -- that can be administered in a clinic without surgery -- could make it easier for patients to follow a prescribed course of monitoring for extended periods of time," Hall said.
The engineers have filed for a provisional patent on the technology and are working to develop it with CARI Therapeutics, a startup based in the Qualcomm Institute Innovation Space at UC San Diego, and Dr. Carla Marienfeld, an addiction psychiatrist at UC San Diego, who specializes in treating substance abuse disorders.
The sensor is coated with alcohol oxidase, which is an enzyme that selectively interacts with alcohol to generate a byproduct to be electrochemically detected. Two additional sensors on the chip measure background signals and pH levels to make the alcohol reading more accurate.
The device uses just 970 nanowatts total, which is roughly one million times less power than a smartphone consumes when making a phone call, the researchers said.
"We don't want the chip to have a significant impact on the battery life of the wearable device," Hall said. "And since we're implanting this, we don't want a lot of heat being locally generated inside the body or a battery that is potentially toxic."
The researchers have tested the device in a mimicked implanted environment using mixtures of ethanol in diluted human serum under layers of pig skin, and are planning to next test it
A test mimicked an implanted environment with mixtures of ethanol in diluted human serum underneath layers of pig skin. They next want to test the chip in live animals.
"This is a proof-of-concept platform technology," Hall said. "We've shown that this chip can work for alcohol, 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."