Scientists have developed a new 'potalyser' - the first practical roadside test for marijuana intoxication, that can detect the drug in a driver's saliva in under three minutes.
No device currently on the market can quickly provide a precise measurement of a driver's marijuana intoxication as effectively as a breathalyser gauges alcohol intoxication, researchers said.
THC, the drug's most potent psychoactive agent, is commonly screened for in laboratory blood or urine tests - not very helpful for an officer in the field.
The device developed by scientists at the Stanford University in the US might function as a practical "potalyser" because it can quickly detect not just the presence of THC in a person's saliva, but also measure its concentration.
Led by Shan Wang, a Stanford professor, the team created a mobile device that uses magnetic biosensors to detect tiny THC molecules in saliva.
Officers could collect a spit sample with a cotton swab and read the results on a smartphone or laptop in as little as three minutes.
Researchers tackling the "potalyser" problem have zeroed in on saliva because testing it is less invasive and because THC in saliva may correlate with impairment better than THC in urine or blood.
Wang's device can detect concentrations of THC in the range of 0 to 50 nanogrammes per millilitre of saliva.
While there is still no consensus on how much THC in a driver's system is too much, previous studies have suggested a cutoff between 2 and 25 nanogrammes per millilitre, well within the capability of the device.
The researchers achieved such precision by harnessing the behaviour of magnetism in nanoparticles, which measure just a few tens of billionths of a metre.
In the test, saliva is mixed with THC antibodies, which bind to any THC molecules in the sample.
Then the sample is placed on a disposable chip cartridge, which contains magnetoresistive (GMR) sensors pre-coated with THC, and inserted into the handheld reader.
The device then uses Bluetooth to communicate results to the screen of a smartphone or laptop.
The platform has potential usefulness beyond THC.
The GMR biosensors in the device could detect any small molecule, meaning that the platform could also test for morphine, heroin, cocaine or other drugs.
With 80 sensors built into it, the GMR biosensor chip could screen a single sample for multiple substances.
The team has already tried screening for morphine with promising results.
The study was published in the journal Analytical Chemistry.
