Image: CalTech

A study published in Nature Nanotechnology has introduced a new wearable biosensor for monitoring fertility hormones, notably oestradiol, in human sweat. This device, resembling a ring and worn on the finger, offers a non-invasive alternative to traditional blood tests for hormone monitoring. The biosensor combines microfluidics, nanoelectronics, and a class of molecules known as aptamers. These aptamers, short strands of DNA or RNA, are designed to specifically bind to the hormone oestradiol. The sensor’s unique construction involves an interface laden with oestradiol-recognizing aptamers and a gold-nanoparticle electrode coated with MXene to enhance electrical signal detection.

Upon wearing the sensor, a small current is generated to stimulate sweat production. The sweat is then drawn into a reservoir where the aptamers exchange preloaded DNA strands, tagged with methylene blue, for oestradiol molecules. These DNA strands migrate to the electrode, where the methylene blue levels are measured to determine hormone concentration. Initial tests with artificial sweat showed the sensor could detect oestradiol in just 10 minutes, at concentrations as low as 140 nanomolar.

The sensor also includes mechanisms to monitor skin temperature, pH, and sweat’s salt concentration, allowing real-time calibration of hormone measurements. These readings can be displayed on a mobile device, offering immediate insights into hormone levels.

“We know, for example, that there are clinically relevant biomarkers present in our sweat, but at extremely low concentrations,” says Wei Gao, a biomedical engineer at the California Institute of Technology in Pasadena and a co-author of the study. So far, no sensors or wearable devices have been developed that specifically target reproductive hormones in sweat. Oestradiol, the focus of the current work, has key roles in fertility and women’s health, areas of research that remain significantly underfunded, despite a “strong demand for technologies that give people more information about their menstrual and fertility status”, he says.

In testing, the sensor’s performance was validated on synthetic sweat before being used by five women to track their menstrual cycles. In a subset of participants, concurrent blood tests were conducted, showing a promising correlation between the sensor and traditional blood test results.

While primarily developed for menstrual cycle tracking, the sensor’s utility extends to other areas of health, including hormone therapy monitoring. The research team is exploring the potential to track multiple hormones simultaneously, which could significantly enhance personalized health monitoring.

This development in wearable health technology represents an important advancement in non-invasive health monitoring, particularly for women’s health. It underscores the potential of such technologies in providing accessible, real-time health data, a critical aspect of personalized healthcare.


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