A newly developed wearable sensor could soon help to detect whether someone has reached the point of ‘burnout’ by measuring cortisol levels in sweat.
The small wearable sensor developed by engineers at EPFL’s Nanoelectronic Devices Laboratory (Nanolab) and Xsensio can be placed directly on a patient’s skin to continually measure the concentration of cortisol – the main biomarker of stress – in a patient’s sweat.
The steroid hormone cortisol is produced by the adrenal glands out of cholesterol and usually controlled by the adrenocorticotropic hormone (ACTH), which is produced by the pituitary gland. When stressed, cortisol helps the body to respond, usually being secreted throughout the day according to a circadian rhythm. People who suffer from stress related diseases have their circadian rhythm thrown off and the body can then produce too much or too little cortisol, leading to heart disease, depression, and burnout.
Measuring cortisol
Amounts of cortisol can be detected in sweat, so Adrian Ionescu, head of Nanolab, developed a wearable smart patch with a miniaturised sensor, containing a transistor and an electrode made from graphene.The graphene is functionalised through aptamers, which are short fragments of single-stranded DNA or RNA that can bind to specific compounds. The aptamer in the patch carries a negative charge, so, when it encounters cortisol, it immediately captures the hormone, causing the strands to fold onto themselves and bringing the charge closer to the electrode surface.
The device then detects the charge and is consequently able to measure the cortisol concentration in the wearer’s sweat, allowing for monitoring of cortisol concentrations continuously throughout the circadian cycle.
Ionescu said: “That’s the key advantage and innovative feature of our device. Because it can be worn, scientists can collect quantitative, objective data on certain stress-related diseases. And they can do so in a non-invasive, precise and instantaneous manner over the full range of cortisol concentrations in human sweat.”
Esmeralda Megally, CEO of Xsensio, says: ” We look forward to testing this new sensor in a hospital setting and unlocking new insight into how our body works.”
The sensor will be tested on patients with Cushing’s syndrome, Addison’s disease, and stress-related obesity by staff of Professor Nelly Pitteloud, who is chief of endocrinology, diabetes, and metabolism at the Lausanne University Hospital (CHUV).
For psychological diseases caused by too much stress, Ionescu said: “For now, they are assessed based only on patients’ perceptions and states of mind, which are often subjective. So, having a reliable, wearable system can help doctors objectively quantify whether a patient is suffering from depression or burnout, for example, and whether their treatment is effective.
“What’s more, doctors would have that information in real time. That would mark a major step forward in the understanding of these diseases.”
