Are you stressed? Nanoparticles pave the way for at-home stress testing

Stress takes many forms in our daily lives, from the relentless demands of work to the constant rush to school. But ignoring high stress levels can lead to serious health problems like depression and Alzheimer’s disease. What if monitoring your stress levels at home became the norm? Thanks to nanoparticles, that possibility is getting closer.

In a new study published in the journal TalantaA team from China and the UK has produced a new and improved sensor that can accurately measure levels of cortisol, a stress biomarker in the blood.

Tong Ji, a part-time PhD student and senior technician at Xi’an Jiaotong-Liverpool University (XJTLU) in China, is the study’s first author. She says: “There has been a long search for a cost-effective, highly reproducible and easy-to-use point-of-care test device that accurately measures cortisol levels.

“This could make a huge difference in the rapid and appropriate diagnosis of high cortisol levels, thereby significantly improving people’s lives.”

Currently available devices typically contain electrodes that are not very stable under different and fluctuating conditions, such as pH and temperature changes. This gives the devices a short lifetime and makes them difficult to produce for commercial purposes.

“Current cortisol sensors have reference electrodes with a silver layer that oxidizes easily and is unstable in electrochemical measurements,” Ji explains.

“In this study, we used iridium oxide nanoparticles to coat the silver layer. This modification improves the stability, sensitivity, and reproducibility of cortisol detection in point-of-care devices.”

Dr. Qiuchen Dong, assistant professor at XJTLU and corresponding author, added: “This is the first time that iridium oxide has been used in this way.

“Our team has developed a simple and inexpensive cortisol measuring device that detects cortisol molecules at a concentration 3,000 times lower than the normal range of cortisol in our blood. This makes our device sensitive enough for commercial use.”

The modified iridium oxide electrodes also improved the selectivity of the tests. Dr Graham Dawson, Associate Professor and co-author of the XJTLU study, said: “One of the problems with current solutions is that there is a high similarity between cortisol and other hormones such as progesterone, testosterone and corticosterone. This means it is difficult for detectors to distinguish between them.

“Our modified iridium oxide electrode is selective enough to distinguish between different hormones and helps solve this problem.”