Reviewed by Alex SmithFeb 8 2022
A hormone called cortisol is produced by the human body in response to stress, from the everyday to the extreme.
Cortisol is well-suited for measurement through wearable devices, according to study co-author Sam Emaminejad, because its concentration levels in sweat are similar to its circulating levels. Image Credit: Yichao Zhao and Zhaoqing Wang/UCLA
Until now, it has been unfeasible to assess cortisol as a way to possibly identify conditions such as post-traumatic stress and depression, wherein levels of the hormone are high.
Traditionally, cortisol levels have been measured via blood samples by professional labs, and while those measurements can be beneficial for diagnosing some diseases, they fail to detect variations in cortisol levels over time.
Currently, a UCLA research team has engineered a device that could be a huge step forward: a smartwatch that measures cortisol levels found in sweat—noninvasively, accurately, and in real-time.
Demonstrated in a study published in Science Advances, the technology could provide wearers the ability to read and react to a crucial biochemical indicator of stress.
I anticipate that the ability to monitor variations in cortisol closely across time will be very instructive for people with psychiatric disorders. They may be able to see something coming or monitor changes in their own personal patterns.
Anne Andrews, Study Co-Corresponding Author and Professor of Psychiatry and Biobehavioral Sciences, UCLA
Anne Andrews is a member of the Semel Institute for Neuroscience and Human Behavior and a UCLA professor of chemistry and biochemistry.
Cortisol is compatible for measurement through sweat, according to co-corresponding author Sam Emaminejad, an associate professor of electrical and computer engineering at the UCLA Samueli School of Engineering, and a member of CNSI.
We determined that by tracking cortisol in sweat, we would be able to monitor such changes in a wearable format, as we have shown before for other small molecules such as metabolites and pharmaceuticals. Because of its small molecular size, cortisol diffuses in sweat with concentration levels that closely reflect its circulating levels.
Sam Emaminejad, Associate Professor of Electrical and Computer Engineering, Samueli School of Engineering, UCLA
The technology makes the most of earlier advances in wearable bioelectronics and biosensing transistors made by Emaminejad, Andrews, and their research groups.
In the new smartwatch, a strip of specialized thin adhesive film captures minute volumes of sweat, measurable in millionths of a liter. An attached sensor identifies cortisol using engineered strands of DNA, known as aptamers, which are made in such a way that a cortisol molecule will fit into each aptamer similar to a key fitting a lock.
When cortisol attaches, the shape of the aptamer changes in a way that changes the electric fields at the surface of a transistor.
The invention—together with a 2021 study that showed the ability to assess important chemicals in the brain using probes—is the result of a prolonged scientific quest for Andrews.
Over 2 decades, she has led efforts to observe molecules such as serotonin, a chemical messenger in the brain connected with mood regulation, in living things, regardless of transistors’ vulnerability to wet, salty biological surroundings.
In 1999, she suggested using nucleic acids—instead of proteins, the typical mechanism—to identify specific molecules.
That strategy led us to crack a fundamental physics problem: how to make transistors work for electronic measurements in biological fluids.
Anne Andrews, Study Co-Corresponding Author and Professor of Psychiatry and Biobehavioral Sciences, UCLA
Meanwhile, Emaminejad has had a vision of universal personal health tracking. His lab is pioneering wearable devices with biosensors that monitor the levels of specific molecules that are associated with particular health measures.
“We’re entering the era of point-of-person monitoring, where instead of going to a doctor to get checked out, the doctor is basically always with us,” he said. “The data are collected, analyzed, and provided right on the body, giving us real-time feedback to improve our health and well-being.”
Emaminejad’s lab had earlier shown that a disposable model of the specialized adhesive film facilitates smartwatches to examine chemicals from sweat, as well as a technology that stimulates small amounts of sweat even when the wearer is stationary.
Previous studies demonstrated that sensors built by Emaminejad’s team could be beneficial for diagnosing diseases such as cystic fibrosis and for customizing drug dosages.
One obstacle in using cortisol levels to identify depression and other disorders is that levels of the hormone can differ extensively from person to person—so doctors cannot learn a lot from any single measurement.
But the researchers anticipate that monitoring individual cortisol levels over time using the smartwatch may warn wearers, and their physicians, to variations that could be clinically important for diagnosis or tracking the effects of treatment.
Among the study’s other authors is Janet Tomiyama, a UCLA associate professor of psychology, who has teamed up with Emaminejad’s lab over the years to test his wearable devices in clinical surroundings.
This work turned into an important paper by drawing together disparate parts of UCLA. It comes from us being close in proximity, not having ego problems, and being excited about working together. We can solve each other’s problems and take this technology in new directions.
Paul Weiss, Study Co-Author and Distinguished Professor of Chemistry and Biochemistry and of Materials Science and Engineering, UCLA
Paul Weiss is also a member of CNSI.
The most recent research is based on early work that was financed by the National Science Foundation and the National Institutes of Health.
The present study received financial assistance from the NSF CAREER program, the National Institute on Drug Abuse through an NIH Director’s Transformative Research Award, the National Institute of General Medical Science of the NIH, the Henry M. Jackson Foundation, the Stanford Genome Technology Center, the Brain and Behavior Foundation, and the PhRMA Foundation.
Instrumentation for the new study was provided by the UCLA NanoLab, Electron Imaging Center for NanoMachines, and Nano and Pico Characterization Laboratory, all housed at CNSI.
The study’s co-first authors are UCLA postdoctoral scholars Bo Wang and Chuanzhen Zhao, a former UCLA graduate student. Other co-authors are Zhaoqing Wang, Xuanbing Cheng, Wenfei Liu, Wenzhuo Yu, Shuyu Lin, Yichao Zhao, Kevin Cheung, and Haisong Lin, all of UCLA; and Milan Stojanović and Kyung-Ae Yang of Columbia University.
Journal Reference:
Wang, B., et al. (2022) Wearable aptamer-field-effect transistor sensing system for noninvasive cortisol monitoring. Science Advances. doi.org/10.1126/sciadv.abk0967.