Saliva tests may help identify marijuana-impaired drivers

Photo by ashton

Photo by ashton

As of the recent election, seven states and the District of Columbia have now legalized marijuana for recreational use and 19 other states have legalized medical marijuana. And this legalization has raised concerns about driving under the influence of marijuana.

A number of research groups are now focusing on ways to identify drivers impaired by marijuana. As recently reported by KQED, the Center of Medicinal Cannabis Research at the University of California, San Diego, are working to “gather data about dosages, time and what it takes to impair driving ability — and then create a viable roadside sobriety test for cannabis.” And a group of Stanford engineers have created a test called a ‘potalyzer.’

The Stanford effort was led by Shan Wang, PhD, a Stanford professor of materials science and engineering and of electrical engineering. He and his colleagues developed a mobile device that detects the amount of tetrahydrocannabinol (THC) molecules in saliva. (THC is the main psychoactive agent in marijuana.)

The test would allow police officers to collect a saliva sample from the driver’s mouth with a cotton swab, analyze it with the new device, and then read the results on a smartphone or laptop in as little as three minutes.

The technology combines magnetic nanotechnology with a competitive immunoassay. During the test, saliva is mixed with antibodies that bind to both THC molecules and magnetic nanoparticles. The mixture is placed on a disposable test chip, inserted into the handheld device and the THC-antibody-nanoparticles are detected by magnetic biosensors. The biosensor signal is then displayed on a Bluetooth-enabled device.

Wang’s group focused on developing a THC saliva test because it is less invasive and may correlate better with impairment than THC urine or blood tests. Also key is the need for a very sensitive test. A Stanford news release explains:

“Wang’s device can detect concentrations of THC in the range of 0 to 50 nanograms per milliliter of saliva. While there’s no consensus on how much THC in a driver’s system is too much, previous studies have suggested a cutoff between 2 and 25 ng/ml, well within the capability of Wang’s device.”

There is still a lot to do before police can deploy this ‘potalyzer’ device, including making it more user-friendly, getting it approved by regulators and investigating whether there is a better biomarker to detect marijuana impairment than THC. In addition, the test may not work well for THC edibles, the researchers wrote in a recent paper published in Analytical Chemistry.

On the upside, the Stanford technology could also be used to test for morphine, heroin, cocaine or other drugs — and for multiple drugs at the same time.

More research is needed, but there is now a new funding source in California: Proposition 64 allots millions of dollars per year to research marijuana and develop ways to identify impaired drivers.

This is an expanded version of my Scope blog story, courtesy of Stanford School of Medicine.

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