Researchers have developed a wearable, non-invasive sensor that can monitor biomarkers of inflammation in the wearer’s sweat. People with chronic inflammatory diseases could use the device at home, they said.
Inflammation has been linked to a range of mental and physical ailments, including the top three global killers: ischemic heart disease, stroke and chronic obstructive pulmonary disease (COPD).
While acute inflammatory responses are the body’s natural way of fighting infection and speeding healing, long-term or chronic inflammation can lead to irreversible tissue damage. Being able to detect inflammation quickly and easily is key to treatment. Measuring blood levels of C-reactive protein (CRP) is commonly used as a biomarker of inflammation, but requires sophisticated laboratory equipment and personnel to analyze blood samples.
Now, researchers at Caltech have developed a new wearable sensor, called InflaStat, that wirelessly and noninvasively monitors inflammation by measuring CRP levels in human sweat.
The researchers had to overcome a few hurdles before they could start making their first sweat-analysis sensor. Mainly CRP is more difficult to detect than other molecules. It is found in much lower concentrations in the blood than other biomarkers, and its molecules are larger, meaning it is more difficult to excrete them from the blood into sweat.
“These are the main issues that have previously prevented people from doing wearable CRP sensing,” said Gao Wei, corresponding author of the study. “We needed high sensitivity to automatically monitor very low concentrations of CRP on the skin.”
The InflaStat is made from laser-engraved graphene, which contains tiny pores that create a large surface area. These pores contain antibodies that bind to CRP and special molecules called redox molecules that generate small electrical currents under certain conditions. Gold nanoparticles are incorporated into the sensor structure, each carrying an independent set of CRP-detecting antibodies.
When CRP molecules from the wearer’s sweat enter the sensor, they attach to the detector antibodies and the antibodies in the graphene pores. The nanoparticles then attach to the graphene and trigger the redox molecules to generate an electrical current, which is read by electronics attached to the sensor.
Since each gold nanoparticle contains many detection antibodies, the signal (very small) is amplified far beyond that produced by a single CRP molecule.
The researchers tested InflaStat on healthy participants, patients with COPD and those who had recovered from COVID-19 infection. They found that the sensor was comfortable to wear and could capture inflammatory biomarkers noninvasively and wirelessly. Data is displayed in real time on a custom smartphone app. As expected, CRP levels were significantly higher in patients with COPD and post-COVID-19 infection than in healthy participants. The researchers found that the sensor could accurately detect CRP levels in sweat relative to blood levels.
The researchers say their findings suggest that their sensor could be used for non-invasive, home-monitoring of chronic diseases such as inflammatory bowel disease or chronic obstructive pulmonary disease. What’s more, they show that it could be adapted to test other trace-level and disease-associated biomarkers.
“This is a general platform that allows us to monitor extremely low levels of molecules in bodily fluids,” Gao said. “We hope to expand this platform to monitor other clinically relevant proteins and hormone molecules. We also want to see if this can be used for chronic disease management. Inflammation represents a risk for many patients. If we can monitor them at home, we can Identify their risks and treat them promptly.”
The study was published in the journal Nature Biomedical Engineering The video below, made by Caltech, shows how the sensor detects CRP.
Wearable sensor detects internal inflammation