Wearable wireless sweat patch uses graphene sensor
Researchers at CalTech in the US have developed a graphene-based wearable sensor that can detect the start of inflammation from sweat.
The wireless sensor detects the C-reactive protein, or CRP, which is secreted by the liver and is commonly associated with inflammation. Its presence in sweat is a strong indicator of an underlying health condition.
CRP is much more difficult to detect than the molecules detected by his other sweat sensors as it is present in the blood at a much lower concentration than other biomarkers says Wei Gao, whose lab is responsible for the development of a variety of wearable sweat sensor,. This is because CRP molecules are much larger than other biomarker molecules and because the molecules are targe and so less can transfer from the bloodstream to sweat.
Wireless patches for detecting molecules in sweat are a key area for wearable medical sensor development as the sensors can be easily applied and monitored.
- Flexible sweat patch provides electrochemical, colorimetric data
- Standalone sweat sensor patch provides immediate readout
“Those were the main issues that prevented people from doing wearable CRP sensing before,” says Gao, assistant professor of medical engineering, Heritage Medical Research Institute Investigator. “We need high sensitivity to monitor very low-concentration CRP automatically on the skin.”
The CRP sensor is built on laser-engraved graphene with many tiny pores that create a large amount of surface area. Those pores are embedded with antibodies that bind to CRP and special molecules (redox molecules) capable of generating a small electric current under certain conditions.
The sensor also contains gold nanoparticles that carry with them a separate set of CRP detector antibodies.
When CRP molecules enter the sensor via sweat, they attach to both the detector antibodies on the gold nanoparticles and the antibodies on the graphene, temporarily gluing the nanoparticles to the graphene and triggering the redox molecule to generate an electrical current that can be measured by electronic components attached to the sensor.
Because each gold nanoparticle contains multiple detector antibodies, they amplify the minuscule signal that a single CRP molecule would otherwise provide, Gao says.
- Flexible skin patch analyses sweat in real-time
- Sweat-powered metabolic sensors wrap around the skin
To account for the influence of variations in sweat compositions from person to person on the electrochemical signal of the biosensor, the sensor was also designed to measure the concentration of ions in the sweat, the sweat’s pH, and skin temperature.
Gao says that the work demonstrates for the first time that sweat CRP can be detected accurately and has good correlation with its counterpart in blood, which has implications for his work in the lab and for practical medical applications.
“This is a general platform that lets us monitor extremely low-level molecules in our body fluids. We hope to expand this platform to monitor other clinically relevant protein and hormone molecules,” he says. “We also want to see if this can be used for chronic disease management. Inflammation means a risk for many patients. If they could be monitored at home, their risk can be identified, and they can be given timely treatment.”
A wireless patch for the monitoring of C-reactive protein in sweat
