A wearable sensor that monitors estradiol by detecting its presence in sweat. (Credit: Caltech)

A wearable sensor monitors estradiol by detecting its presence in sweat. The researchers say the sensor may one day make it easier for women to monitor their estradiol levels at home and in real time.

The primary challenge, and what dictated changes in the sensor's design this time around, is that estradiol, which already is present at fairly low levels in the blood, is roughly 50 times less concentrated in sweat.

For the new sensor, the research team made use of short single-stranded DNA known as aptamers. Aptamers work as artificial antibodies and are designed to bind specifically to a target molecule. The aptamers are attached to a surface modified with gold nanoparticles and bind to single-stranded DNA molecules tagged with a molecule that can directly donate or accept electrons under certain conditions.

When an aptamer binds to an estradiol molecule, it releases the redox molecule. That molecule is recaptured by a nearby electrode made of MXene-coated gold nanoparticles, generating an electrical signal that correlates with the estradiol level. That hardware then wirelessly transmits the data it collects to an app that runs on a smart phone, providing a simple interface for the user.