Wearable microneedle patch detects fentanyl and automatically releases naloxone

Researchers at Virginia Tech have created a wearable patch smaller than a penny that can detect fentanyl in the body and automatically deliver naloxone, the medication used to reverse opioid overdoses. The device, called the iNal patch, uses an array of 121 microscopic needles to access interstitial fluid just beneath the skin. Inside the patch, porous silica nanoparticles loaded with naloxone are sealed by fentanyl-sensitive molecular gates that open when the opioid is present, releasing the antidote in proportion to the detected concentration.

The patch was developed by a team led by Wujin Sun, assistant professor of biological systems engineering, with Penghui Zhao as first author. Their findings were published in Advanced Science. Because only a portion of the nanoparticle pores open during each exposure, the patch retains naloxone for potential future fentanyl events, addressing the risk that naloxone's effects may wear off before the opioid clears the body.

In laboratory tests, the system responded within minutes and continued releasing naloxone for up to 24 hours, with higher fentanyl concentrations triggering larger releases. The researchers then evaluated the patch in mice, where it released more naloxone as fentanyl doses increased and responded through at least three separate fentanyl exposures. Mice treated with the patch showed substantially fewer opioid-induced symptoms than untreated mice, and no significant irritation or harmful effects were observed.

Sun describes the device as a harm-reduction tool rather than a replacement for medical care, noting that accidental overdoses can occur when patients become confused about dosing schedules. The sensor is designed to monitor opioid concentration and trigger naloxone release only when a threshold is exceeded. Although demonstrated with fentanyl and naloxone, the underlying chemistry could be adapted for other opioids and antagonists.

The project began in 2022 and involved collaborators from Virginia Tech's College of Science, School of Neuroscience, the University of Wisconsin–Madison, the University of California Riverside, and the University of Sydney. Sun and Zhao have filed a patent application, and further research is needed to assess long-term durability, performance across different skin types and real-world conditions, and accuracy with other opioids before clinical use could be considered.