It is difficult to objectively measure just how stressed a person is, especially in real time and with continuous monitoring, which can help people see patterns of behaviour and acitivites that make them more or less stressed and then take steps to correct this. But a new device developed by scientists at the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland may be able to do just that.
The EPFL's Nanolab has developed a wearable smart patch with a miniaturized sensor, which uses sweat as the detection fluid in order to monitor cortisol concentrations continuously throughout the circadian cycle. "Disorders such as obesity, metabolic syndrome, type two diabetes, heart diseases, allergy, anxiety, depression, fatigue syndrome, and burnout are often associated with dysfunctions of the stress axes," say the researchers. "Both high and low levels of cortisol, as well as disrupted circadian rhythms, are implicated in physical and psychological disorders."
The patch contains a transistor and an electrode made from graphene which, due to its unique proprieties, offers high sensitivity and very low detection limits. The graphene is functionalized through aptamers, which are short fragments of single-stranded DNA or RNA that can bind to specific compounds. The aptamer in the EPFL patch carries a negative charge; when it comes into contact with 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, reported Science Daily.
Recently, there has been an increasing interest in sensing cortisol biomarker in biofluids for numerous diseases related to the stress, EPFL scientists said. As the secreted cortisol enters into the circulatory system, it can be found in detectable quantities in several biofluids in human body including saliva, sweat and urine. When we’re in a stressful situation, whether life-threatening or mundane, cortisol is the hormone that takes over. It instructs our bodies to direct the required energy to our brain, muscles and heart. “Cortisol can be secreted on impulse–you feel fine and suddenly something happens that puts you under stress, and your body starts producing more of the hormone,” says Adrian Ionescu, head of EPFL's Nanolab. While cortisol helps us respond to stressful situations, and is secreted through the day according to a circadian rhythm, usually peaking between 6am and 8am and gradually decreasing during the day, it can be a double-edged sword.
“In people who suffer from stress-related diseases, this circadian rhythm is completely thrown off,” says Ionescu. “And if the body makes too much or not enough cortisol, that can seriously damage an individual’s health, potentially leading to obesity, cardiovascular disease, depression or burnout,” Ionescu told Neuroscience News.