Researchers at North Carolina State University have developed a self-powered microneedle patch designed to monitor health biomarkers without the need for blood samples, batteries, or external devices. The patch was tested on synthetic skin and demonstrated the ability to collect biomarker samples over periods ranging from 15 minutes to 24 hours.
“Biomarkers are measurable indicators of biological processes, which can help us monitor health and diagnose medical conditions,” said Michael Daniele, corresponding author of the study. “The vast majority of conventional biomarker testing relies on taking blood samples. In addition to being unpleasant for most people, blood samples also pose challenges for health professionals and technology developers. That’s because blood is a complex system, and you need to remove the platelets, red blood cells, and so on before you can test the relevant fluid.
“The patch we’ve developed uses microneedles to sample the fluid that surrounds cells in the dermal and epidermal layers just below the very top layer of cells that make up your skin,” Daniele explained. “This is called dermal interstitial fluid (ISF), and it contains almost all of the same biomarkers found in blood. What’s more, ISF makes for a ‘cleaner’ sample – it doesn’t need to be processed the way blood does before you can test it. Essentially, it streamlines the biomarker testing process.”
The new patch operates passively without requiring batteries or an external power source. It consists of four layers: a polymer housing visible on the surface; a gel layer; a paper layer; and microneedles made from material that swells upon contact with ISF. The ISF wicks through these microneedles into the paper layer, where it is stored after being drawn by osmotic pressure created by glycerol in the gel.
“The paper is where the ISF is stored,” Daniele stated. “When you take the patch off, you remove the paper strip and analyze the sample.”
Testing involved two synthetic skin models. According to Daniele, “It worked well. The patches collected measurable results in as little as 15 minutes and were capable of storing the biomarker samples for at least 24 hours.”
For their initial tests, researchers monitored cortisol levels—a stress-related biomarker known to fluctuate throughout the day.
“That means it’s something people may want to monitor multiple times a day without having to draw blood repeatedly,” Daniele said. “And there’s no reason the patch wouldn’t work for many of the biomarkers found in ISF.”
Materials used in making these patches are relatively inexpensive and widely available. Manufacturing costs would primarily stem from producing microneedles but are expected to be competitive with traditional blood testing methods.
“The highest cost of the patches would be manufacturing the microneedles, but we think the price would be competitive with the costs associated with blood testing,” Daniele noted. “Drawing blood requires vials, needles and – usually – a phlebotomist. The patch doesn’t require any of those things.”
Human trials have already begun using these patches, alongside development of electronic devices capable of reading biomarker levels from collected samples.
“We’ve already developed an electronic device that can ‘read’ cortisol levels from the paper strip and are working on another device that evaluates a different biomarker,” Daniele said.
“We’re now looking for industry partners on two fronts. We’d love to talk with companies in the diagnostic space to explore additional applications, and we’d also like to talk with potential partners about scaling up production.”
The research was published open access in Lab on a Chip under DOI: 10.1039/D5LC00590F. Co-lead authors include Christopher Sharkey (NC State), Angélica Aroche (NC State/UNC Chapel Hill), Isabella Agusta (NC State/UNC Chapel Hill), along with other contributors from NC State University.
Funding came from several sources including grants from National Science Foundation’s Center for Advanced Self-Powered Systems of Sensors and Technologies (ASSIST), NC State Institute for Connected Sensor-Systems, Chancellor’s Innovation Fund at NC State, and SEMI-NBMC under grants NB18-21-26 and NB18-24-38.
Daniele is an officer and founder of DermiSense Inc., which works on commercializing microneedle-based technologies.
