Engineers develop the 'potalyzer,' a roadside saliva test for marijuana intoxication

September 9, 2016 by Carrie Kirby, Stanford University
Engineers develop the 'potalyzer,' a roadside saliva test for marijuana intoxication
Stanford engineers are developing a portable device that measures THC levels in saliva, a step toward creating a roadside test for driving under the influence of marijuana. Credit: Reuters/Rick Wilking

This November, several states will vote whether to legalize marijuana use, joining more than 20 states that already allow some form of cannabis use. This has prompted a need for effective tools for police to determine on the spot whether people are driving under the influence.

Stanford researchers have devised a potential solution, applying magnetic nanotechnology, previously used as a cancer screen, to create what could be the first practical roadside test for marijuana intoxication.

While police are trying out potential tools, no currently on the market has been shown to quickly provide a precise measurement of a driver's marijuana intoxication as effectively as a breathalyzer gauges alcohol intoxication. 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 Stanford device might function as a practical "potalyzer" because it can quickly detect not just the presence of THC in a person's , but also measure its concentration.

Led by Shan Wang, a professor of materials science and engineering and of electrical engineering, the Stanford 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 "potalyzer" 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. The big challenge is that these spit tests may be called upon to detect superlatively tiny concentrations of THC. Some states have no set limit of THC in the body for drivers, while others set a limit of 0 or 5 nanograms (a billionth of a gram) per milliliter of blood.

Wang's device can detect concentrations of THC in the range of 0 to 50 nanograms per milliliter of saliva. While there's 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 ng/mL, well within the capability of Wang's device.

Repurposing biomedical tools

The researchers achieved such precision by harnessing the behavior of magnetism in nanoparticles, which measure just a few tens of billionths of a meter.

The Wang Group has been exploring magnetic nanotechnology for years, using it to attack such diverse problems as in vitro cancer diagnostics and magnetic information storage. In this case, they're combining magnetic nanotechnology with the time-tested biochemical technique of the immunoassay. Immunoassays detect a certain molecule in a solution by introducing an antibody that will bind only to that molecule.

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.

This sets in motion a "competition" between the THC pre-coated on the sensor and THC in the saliva to bind with the antibodies; the more THC in the saliva, the fewer antibodies will be available to bind to the THC on the sensor surface.

The number of antibodies bound to THC molecules on the sensor tells the device how many antibodies the THC in the sample used up, and therefore how many THC molecules were present in the sample.

Next, magnetic nanoparticles, specially made to bind only to the antibodies, are introduced to the sample. Each nanoparticle binds onto a THC-antibody pair like a sticky beacon, but only the molecules on the sensor surface will be close enough to trip the GMR biosensors in the reader. The device then uses Bluetooth to communicate results to the screen of a smartphone or laptop.

"To the best of our knowledge, this is the first demonstration that GMR biosensors are capable of detecting small molecules," Wang wrote in a paper describing the device, published in Analytical Chemistry.

Beyond marijuana

The platform has potential usefulness beyond THC. Just as they do with 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.

In fact, 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.

Students are currently working on creating a user-friendly form factor for the device, which would need to go through field tests and be approved by regulators before it can be deployed by police.

Another thing that would have to happen before the device would be useful to law enforcement: State laws must set limits for the concentration of THC allowed in a driver's saliva.

Here too, the Wang Group's device could be helpful. For example, the next generation of the device could screen both the blood and saliva of a subject to establish an understanding of the correlation between blood THC level and saliva THC level at the same degree of intoxication.

Explore further: Colorado town awaits test results of pot ingredient in water

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Scientific basis for laws on marijuana, driving questioned

May 10, 2016

Motorists are being convicted of driving under the influence of marijuana based on arbitrary state standards that have no connection to whether the driver was actually impaired, says a study by the nation's largest auto club.

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Anonym
3.4 / 5 (10) Sep 09, 2016
Just because you can build it, doesn't mean anyone should buy it. .... No one has shown significant impairment of experienced drivers : studies have repeatedly found that accident rates fall when people substitute cannabis/marijuana for alcohol. People have been driving stoned in large numbers for at least 40 years -- if there were any serious impairment it would have been recognized and legislated against long ago (the first DWI laws were passed in 1910 --- when there is a real problem lawmakers respond fairly quickly). The 'potalyzer' developer hopes to profit from the fading meme that marijuana is a dangerous drug (hey, it's Schedule 1, isn't it!) . This would be pathetic, not to say laughable, but people's lives are still being screwed up by stooopid racist drug prohibition.
Eikka
1.7 / 5 (11) Sep 09, 2016
people's lives are still being screwed up by stooopid racist drug prohibition.


How can a drug prohibition be racist, unless you claim the use of certain drugs is dependent on race? Wouldn't that be racist as well?

No one has shown significant impairment of experienced drivers


The law is written for all drivers equally and there are no special privileges. Whether you're a WRC champion doesn't matter, because the intent is to protect people from those inexperienced drivers.

The problem is that people get a tolerance for pot and it gets fairly high, so there are people who simply won't be able to function right under the same influence as your "experienced driver" who isn't phased by smoking a joint. Peoples' reactions differ.

Pot DWI hadn't been such a big issue before because it is illegal anyhow and the use is somewhat restricted. With legalization, the use of cannabis will multiply and so will the problems.
Eikka
2 / 5 (8) Sep 09, 2016
studies have repeatedly found that accident rates fall when people substitute cannabis/marijuana for alcohol


Studies have also found that cannabis does impair a person's ability to pay attention and operate machinery, and also impairs their ability to judge their own performance correctly. It creates a dunning-kruger effect where the person is blind to their own mistakes.

It's the same thing as with alcohol. The difference is that while alcohol removes inhibitions and makes people act risky, certain varieties of pot tends to make people paranoid and weird, while other varieties make people stupid and slow, much like a geriatric who should have had their license removed.

Alcohol related driving accidents happen because the people get over-confident and negligent and sloppy, whereas THC related accidents involve people behaving in weird ways and reacting to cues too late. The latter is mostly just a nuisance, because people are already primed for bad drivers.
Eikka
2 / 5 (8) Sep 09, 2016
So in other words, the other people accomodate by being a bit paranoid themselves and leaving room for bad driving. E.g. people quickly learn to approach a city bus from behind with caution because they're known to pull off in front of you randomly.

But the traffic can only tolerate so much bad driving before the rules of the road start breaking down and things go south. For example, if you can't trust at all that a person who has a turn signal on will really make that turn, how will you behave? It increases the cognitive load of other drivers, diverts attention to the bad drivers, and so causes more accidents indirectly.

If there's a lot of people driving impaired like that, doing stupid things without realizing it, the overall accident rates go up and the blame gets shared even though the real culprit is the stupid person who drives like a moron, having made themselves stupid by smoking pot.
pntaylor
2.5 / 5 (8) Sep 09, 2016
@Anonym - Spoken like a true pothead.

@Eikka - The man of a thousand words, rambling on, as usual.
RichManJoe
4.2 / 5 (5) Sep 09, 2016
This device measures concentration, and, unlike alcohol, it has been scientifically documented that THC concentration does not indicate intoxication. I have also seen people who take one toke and can't walk while another person can smoke an entire cigarette and not show any effect. In my belief, there needs to be a better test for intoxication, such as possibly some feedback mechanism such as a measuring light vs. eye movement or dilation, or possibly brain wave response. This would catch DUI for alcohol and other drugs, such as medication or illness and not be dependent on concentration in the body.
retrosurf
4.2 / 5 (5) Sep 09, 2016
In the United States, vehicle code infractions are more a means of revenue generation for police department budgets than a means of protecting the public from bad driving. Accurately measuring THC and 11-hydroxy-THC concentrations when there is poor correlation with actual impairment is another tool for the police to use for revenue collection, which is an inherently corrupt practice.

Here's a quote from the National Highway Transportation Safety Administration:

"It is inadvisable to try and predict effects based on blood THC concentrations alone, and currently impossible to predict specific effects based on THC-COOH concentrations. It is possible for a person to be affected by marijuana use with concentrations of THC in their blood below the limit of detection of the method."

(from http://www.nhtsa....bis.htm)
retrosurf
1 / 5 (2) Sep 09, 2016
@Anonym - ...

@Eikka - ...


Try instead @ rem instead of @ hominem.

Thnder
3.9 / 5 (7) Sep 09, 2016

How can a drug prohibition be racist, unless you claim the use of certain drugs is dependent on race? Wouldn't that be racist as well?


When it disproportionately locks up higher numbers of minority ethnicities.
Eikka
2.1 / 5 (7) Sep 09, 2016

How can a drug prohibition be racist, unless you claim the use of certain drugs is dependent on race? Wouldn't that be racist as well?


When it disproportionately locks up higher numbers of minority ethnicities.


But that has nothing to do with racism, because it doesn't target people by race, but by the drug they use.

Imagine if for a simple happenstance a great portion of Australian aboriginals in a particular town were cleptomaniacs. Would that mean a law against shoplifting is racist because the jail would be full of these people?

It would be racist if the police were targeting minorities for drug offences while letting the majority off the hook, but the law against drugs itself can't be racist as it applies to everyone. It's how you enforce the law.

It's a bad argument against a law to say that it's applied wrong. The fix is to apply it right instead of abolishing the law.
Eikka
2.3 / 5 (6) Sep 09, 2016
I have also seen people who take one toke and can't walk while another person can smoke an entire cigarette and not show any effect.


And it's because you can't actually measure who will be impaired enough to be unable to drive safely that you need to limit everyone to a level that is safe for most.

The police can't know if your personal tolerance is high enough that a certain concentration in your blood won't make a difference, and they would be risking the death or injury of other people to let you go.

It's the same as how some people can drive perfectly fine while drunk over the limit, and a great number of other people can't. What would you do? Apply personal DUI limits in the driver's license?

Try instead @ rem instead of @ hominem.


Neither actually counters the point.
TheGhostofOtto1923
3.2 / 5 (9) Sep 09, 2016
No one has shown significant impairment of experienced drivers : studies have repeatedly found that accident rates fall when people substitute cannabis/marijuana for alcohol.
-So youre saying that being stoned out of your mind has absolutely no effect on your reaction time and your ability to make quick decisions? Who are you trying to fool?

If you're going to provide phantom evidence then you should at least provide phantom links to it.

"A new report by the American Auto Association (AAA) has found that the percentage of drivers who are high on pot during fatal accidents in Washington State more than doubled between 2013 and 2014."
TheGhostofOtto1923
4 / 5 (8) Sep 09, 2016
The police can't know if your personal tolerance is high enough that a certain concentration in your blood
Some people can drive very well when drunk. Laws establish minimum standards based on statistics and studies. Doesn't matter what you personally are or aren't capable of.
Manfred Particleboard
3.7 / 5 (6) Sep 09, 2016
Prejudiced I think is the word Anon was looking for. Drug policies are almost always devoid of reason when it comes to making them. In the same way reporting is biased towards the "Somebody think of the children!!" sector. People want their drugs, yet anyone who supplies them are always referred to as 'pushers' 'peddlers' or 'dealers in death'. No one can publically admit to using a drug unless they are an addict, reformed addict, or 'might have inhaled once'. The real data tells a story of a large sector of the community who function just fine with their usage and are unable to ever voice that opinion. I heard a story of a judge who was terrified of the prospect of truck drivers using speed, I find it funny that the airforce gave it to pilots in command of a nuclear weapon. (that's probably old data now, they use more modern drugs i'd like to think) However, the roads aren't a post apocalyptic warzone despite the fact there is a lot of drug use out there on a daily basis.
Steve 200mph Cruiz
5 / 5 (5) Sep 09, 2016
Good, we had a serious budget shortage for a minute.

Everyone is on drugs in this country.
Few things mess you up worse than alcohol. Just keep it at alcohol DUI's, if we start screening for every single drug that impairs you, we will shut down the economy.
gkam
1.5 / 5 (8) Sep 09, 2016
Why do you think Silicon Valley is so inventive?
h20dr
3.4 / 5 (5) Sep 10, 2016
One, all this is just a money grab.

Two, someone will come up with a way to defeat it. (Think of gum or lozenge u pop as your being pulled over that can deactivate the thc).

Seems to me, all you would have to do is is take a drink of water or some other liquid and now you have diluted the saliva so that the reading is not representative of the thc present or the actual state of consciousness of the individual being tested.
h20dr
3 / 5 (2) Sep 10, 2016
Silicon Valley is inventive? What have they invented lately? The new iphone 7 is a pretty good representation of the lack of inventiveness these days.
Zzzzzzzz
3 / 5 (6) Sep 10, 2016
But that has nothing to do with racism, because it doesn't target people by race, but by the drug they use.

Imagine if for a simple happenstance a great portion of Australian aboriginals in a particular town were cleptomaniacs. Would that mean a law against shoplifting is racist because the jail would be full of these people?

It would be racist if the police were targeting minorities for drug offences while letting the majority off the hook, but the law against drugs itself can't be racist as it applies to everyone. It's how you enforce the law.

It's a bad argument against a law to say that it's applied wrong. The fix is to apply it right instead of abolishing the law.

Eikka is either a racist or ignorant of criminal justice systems.
Eikka
1 / 5 (2) Sep 11, 2016
Eikka is either a racist or ignorant of criminal justice systems.


Or I'm simply making a difference between the law and the criminal justice system.

The law and its enforcement are two different things. A law that applies to everyone cannot by definition be racist, and implying that it is racist because members of a race break the law more often is simply being racist yourself because you're discriminating people into races to make the argument in the first place.

How the law is being enforced can be. The criminal justice system can be corrupt - that doesn't mean the law should be abolished.

ForFreeMinds
5 / 5 (2) Sep 11, 2016
Lacking from this tool, is any correlation to THC in the saliva, or correlation of THC in the saliva to THC in the bloodstream, and most importantly correlation of THC in saliva to impaired driving. THC can remain in your system for 30 days after smoking it, while you are only high for perhaps 3 hours.

"How can a drug prohibition be racist"
When racist police selectively enforce the law to arrest people of races they don't like, so they get more arrests and more money.

As for the people who equate marijuana to alcohol, they obviously haven't smoked any pot. Alcohol's effects on "impairment" are obviously so much greater in many ways. For example, it's easy to die of an alcohol overdose, and many do, but no one has ever died from consuming too much pot. And they've done research comparing drunk drivers to stoned drivers https://www.washi...ta-show/ Stoners are far safer.
ForFreeMinds
4.2 / 5 (5) Sep 11, 2016
The idea that we should arrest people in jail for putting themselves in situations where they are more likely to accidentally harm themselves or others, rather than say actually harming others, is debatable. Should we make it illegal to drive on only 4 hours of sleep? How about for people who can only see out of one eye? Should it be illegal to drive if your right foot is in a cast? What if you've a high fever and you want to drive to the hospital? How about a mom driving 5 screaming kids somewhere? I'd say everyone of these actions endangers others just as much as driving stoned. Then shouldn't these actions then be illegal, and shouldn't we give police/judges the discretion to arrest and fine/jail these folks?

The government likes laws against victimless actions, because it gives them control over those who engage in such behavior. There should be no laws against victimless crimes, because then government harms people, when no one else was harmed.
gkam
1.6 / 5 (7) Sep 11, 2016
It is not government, but the blue-noses in it who cause the harm to the rest of us. Many of those overly-religious folk stay awake at night fearing that somewhere, somehow, someone is having fun.
TheGhostofOtto1923
3 / 5 (8) Sep 11, 2016
It is not government, but the blue-noses in it who cause the harm to the rest of us. Many of those overly-religious folk stay awake at night fearing that somewhere, somehow, someone is having fun.
So you admit that you've been a doper for the last 40 years because it's fun, and not because of the war wounds you sustained while touring the Thai countryside on your scooter?

Stoned?

Keep a psychopath talking, sooner or later you get to know who and what they really are.
TheGhostofOtto1923
3 / 5 (8) Sep 11, 2016
no one has ever died from consuming too much pot
More rubbish.

"... suspected fatal cannabis intoxications where full post-mortem investigations… were carried out," researchers said in the study, published in Forensic Science International this month. "After exclusion of other causes of death we assume that the young men experienced fatal cardiovascular complications evoked by smoking cannabis."
Should we make it illegal to drive on only 4 hours of sleep? How about for people who can only see out of one eye? Should it be illegal to drive if your right foot is in a cast? What if you've a high fever and you want to drive to the hospital? How about a mom driving 5 screaming kids somewhere? I'd say everyone of these actions endangers others
Indeed. There are many laws which make distracted and impaired driving a crime especially if it results in bodily injury or death.

For instance if you choose to drive with a cast on and kill somebody you will be liable.
TheGhostofOtto1923
3.7 / 5 (6) Sep 11, 2016
"The National Highway Transportation and Safety Board recommends not driving with a splint or immobilization device..."

""If a patient has had surgery and is seen wearing a restrictive device when getting out of the car following a collision, they can expect that fact to be noted by investigators as well as other parties and likely will be listed as a contributing cause of the wreck," he said."

-Sued and screwed.
gkam
1.6 / 5 (7) Sep 11, 2016
Nobody cares what you copy and paste "otto".

Internet snipers hiding behind phony names are seldom read by others. Perhaps if you had some education or experience to back up your little internet searches, you could pull it off. But you are like the Putin agents in these fora, crude and unconvincing.
h20dr
3.7 / 5 (3) Sep 12, 2016
Reading some of these posts from uninformed goody two shoes is like revisiting Reefer Madness. Almost as entertaining as the actual movie.
TheGhostofOtto1923
3.3 / 5 (7) Sep 12, 2016
Nobody cares what you copy and paste "otto".

Internet snipers hiding behind phony names
How touching george kamburoff wants otto to jump through his hoop because it means so much to him.

What's amatter you feeling lonely so late at night?

Of course lying cheating psychopaths have disdain for valid info because it makes it so much harder for them to make up their own and get away with it.

Georges long history of lying and cheating is valid reference data on his psychopathy. Google him like his family, friends, neighbors, and potential clients have done-
antialias_physorg
3.7 / 5 (3) Sep 12, 2016
No one has shown significant impairment of experienced drivers

Not everyone is an experienced driver. And the law also doesn't (and shouldn't) make a distinction between experienced and non-experienced drivers.

found that accident rates fall when people substitute cannabis/marijuana for alcohol

Which makes ...what kind of point, exactly? Just because shooting someone in the leg is better than shooting someone in the head doesn't make the former legal (or good). Not drinking/smoking reduces the number of accidents the most.

Lacking from this tool, is any correlation to THC in the saliva, or correlation of THC in the saliva to THC in the bloodstream,

What kind of correlation would you expect that would invalidate this method? Inverse? THC in the saliva with none in the bloodstream? Neither seems plausible.
TheGhostofOtto1923
3.3 / 5 (7) Sep 12, 2016
no one has shown significant impairment
LIE.

"Subjects seemed well aware of their impairment in
both tests. Their self-ratings of driving quality
varied over conditions in general agreement with
the objective measurement. The instructors rated
their driving quality as even lower but the dierences
in these assessments were not very large. Some
subjects, particularly after THC 200 mg/kg alone or
in combination with alcohol, indicated that they had
failed the tests. Why they continued to drive in these
conditions is a good question. They probably would
not have proceeded, nor undertaken the tests in the
®rst place, were it not for their reliance on the
instructors to prevent untoward consequences."

"Consequently, THC
smokers in the driving population can generally be
expected to withdraw from legal regulations
regarding drugs... When they do, our data
suggest that they pose a serious threat to themselves
and the general public."
TheGhostofOtto1923
3.3 / 5 (7) Sep 12, 2016
Not everyone is an experienced driver. And the law also doesn't (and shouldn't) make a distinction between experienced and non-experienced drivers
I marvel at aa's disdain for research when this info is so easy to find.
Zzzzzzzz
3 / 5 (6) Sep 12, 2016
The law and its enforcement are two different things. A law that applies to everyone cannot by definition be racist, and implying that it is racist because members of a race break the law more often is simply being racist yourself because you're discriminating people into races to make the argument in the first place.

How the law is being enforced can be. The criminal justice system can be corrupt - that doesn't mean the law should be abolished.

Wrong again. Many times law is enacted with an eye towards unequal enforcement. Wake up and notice reality.
antialias_physorg
3.7 / 5 (3) Sep 12, 2016
Many times law is enacted with an eye towards unequal enforcement.

One can certainly point to zoning law. Possibly voter registration laws. But laws regarding substance abuse? That's about the dangers of the substance - not about race.

I for one would prefer if such a test (that is - in principle - capable for testing for a myriad of consciousness altering substances) were put to widespread use. I do not relish people being on the road unfit to drive...and I don't care whether they are white and unfit to drive or black and unfit to drive. In the event of an accident that is completely irrelevant.
TheGhostofOtto1923
3.4 / 5 (5) Sep 12, 2016
The law and its enforcement are two different things. A law that applies to everyone cannot by definition be racist, and implying that it is racist because members of a race break the law more often is simply being racist yourself because you're discriminating people into races to make the argument in the first place.

How the law is being enforced can be. The criminal justice system can be corrupt - that doesn't mean the law should be abolished.

Wrong again. Many times law is enacted with an eye towards unequal enforcement. Wake up and notice reality.
Well then you should be able to provide some examples.

Got any?

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