Catching opioids on the GO: graphene oxide sensors to detect morphine in urine

New graphene-based sensors could be used by police to detect opiate abuse using suspects' urine samples. Scientists from the Graphene Flagship partners Consiglio Nazionale delle Ricerche (CNR), Italy, and Chalmers University of Technology, Sweden, together with a team at the University of Modena, Italy, created a new qualitative graphene-based sensor for morphine.

Morphine is the main metabolite of heroin. The new sensor provides a fast-acting 'rough test' that yields a positive response if morphine concentration in urine exceeds a certain threshold. The sensor could be used by police forces during criminal investigations and roadside stops, in a similar way to how breathalysers are used to test alcohol levels in suspected drunk drivers. The leader of the study, Chiara Zanardi, from the University of Modena, says: "My goal is to try to use this sensor on the street, on the road, or on the job. It is required only to say if you are safe/healthy or if you have drugs in your system – there is no quantification of morphine."

According to European regulation, sensors should give a positive result for a morphine drug test, if its levels are above 200 parts per billion – or 0.2 milligrams per litre – in the urine. The new device developed by Graphene Flagship researchers produces a detectable signal when morphine concentration in urine surpasses this limit. After administering the test, suspects with a morphine level over the limit could then be investigated further or detained by police.

The device is composed of screen-printed electrodes coated with graphene oxide (GO), electrochemically produced in the laboratories of Graphene Flagship Partner CNR. Graphene oxide acts as an electrocatalytic platform which attracts morphine molecules and oxidises them on contact. Electron flux is released every time a morphine molecule is oxidised, which in turn produces a signal that can be detected and displayed by the device.

The GO electrodes were initially tested in a synthetic urine sample, then applied to real adult urine samples doped with morphine. The device successfully detected morphine in all samples tested. "I observed that I could get a signal of morphine in urine, even when the morphine was present in very low concentrations," comments Zanardi. And graphene is responsible for this effect: "When I compared this to other electrode materials, I observed that graphene performed significantly better in detecting morphine at the required detection limits than any other materials reported to date in previous studies." The next step will be to apply the sensor to pre-tested urine samples provided by drug users. If successful, the goal is to develop an automated handheld drug-testing device for police to use on the job.

Maurizio Prato, Graphene Flagship Work Package Leader for Health and Environment said: "This new sensor could be an excellent application of graphene-based materials. The electrochemically exfoliated GO has unique properties. It is able to transfer electrons, a feature that other types of GO can't do. In addition, the oxygenated functions of the exfoliated GO attract morphine in an efficient way. The combination of these two characteristics makes this material ideal for a highly sensitive sensor of morphine."

Andrea C. Ferrari, Science and Technology Officer of the Graphene Flagship and Chair of its Management Panel, adds: "As the Graphene Flagship progresses on its technology and innovation roadmap, more devices are developed addressing a large number of needs. This work shows yet again the versatility of graphene as sensor material, paving the way for its use in everyday applications"

Reference

'Highly sensitive amperometric sensor for morphine detection based on electrochemically exfoliated graphene oxide. Application in screening tests of urine samples.' Sensors & Actuators B, 2019, 281, 739-745. Giulio Maccaferri, Fabio Terzi, Zhenyuan Xia, Fabio Vulcano, Andrea Liscio, Vincenzo Palermo and Chiara Zanardia. DOI: 10.1016/j.snb.201810163.