The new sensor, however, is six orders of magnitude more sensitive than any electrochemical sensor for the drug reported in the past five years. Besides carbon and gold, the key to its effectiveness is the incorporation of fentanyl antibodies.
“We’re using nature’s invention, so to speak,” lead researcher Alexander Star said in a media statement. “That’s how we can reach these ultralow levels of detection.”
Inspired by covid and pot
The sensor is a modified version of a covid-19 sensor developed by Star’s research group in 2020. The covid sensor is itself an adaptation of a THC breath test—similar to a Breathalyzer, but for marijuana—he developed in 2019.
The core of each of these sensors is made of a chip with carbon nanotubes attached. Each tube is like a tiny wire that’s 100,000 times smaller than a human hair and effective at conducting electricity. Attached to the nanotubes are gold nanoparticles, each about 43 nanometers tall.
In practice, molecules of fentanyl bind to the nanoparticles, triggering a current that flows through the nanotubes. Different substances create different currents; using machine learning, the sensor was able to identify a fentanyl molecule. It also had a 91% success rate when it came to differentiating fentanyl from other opioids, which is helpful when trying to determine whether another drug has been tainted with fentanyl.
To reach its unprecedented level of sensitivity, Star and his team took a cue from the covid sensor and incorporated fentanyl antibodies, attaching them to the nanoparticles. Fentanyl molecules would tightly bind to any antibodies they encountered, changing the current flowing from the antibodies into the nanotubes, signalling the presence of the drug.
The result was a sensor capable of detecting fentanyl on the femtomolar scale. That’s 10-15 moles per liter. The next closest sensor can detect on the nanomolar scale, which is 10-9 moles per litre.
“Nature developed these selective receptors,” Star said. “We adapted them on our platform, the carbon nanotubes.”
In addition to its sensitivity, another benefit of the new device is its portability. To detect such small quantities of fentanyl today requires a mass spectrometer—not a particularly mobile technology. Star’s sensor is small enough to be hand-held and inexpensive enough to be practical.
In the future, the researcher anticipates using this technique to develop a sensor array that can detect many kinds of drugs.
