Tuesday, August 4, 2009
New Roadside Testing Device for Marijuana!
Device Offers a Roadside Dope Test
The system uses magnetic nanoparticles to detect traces of cocaine,
heroin, cannabis, and methamphetamine.
By Alexander Gelfand
Tuesday, August 04, 2009
Photo: http://www.technolo gyreview. com/files/ 31942/biodetect_ x220.jpg
Photo Caption: Quick fix: Philips' drug tester uses a cartridge
containing magnetic nanoparticles and a handheld analyzer. Frustrated
total internal reflection (FTIR) is used to detect five major
recreational drugs in 90 seconds.
Credit: Philips Research
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Later this year, Philips will introduce a handheld electronic device
that uses magnetic nanoparticles to screen for five major recreational
The device is intended for roadside use by law enforcement agencies and
includes a disposable plastic cartridge and a handheld analyzer. The
cartridge has two components: a sample collector for gathering saliva
and a measurement chamber containing magnetic nanoparticles. The
particles are coated with ligands that bind to one of five different
drug groups: cocaine, heroin, cannabis, amphetamine, and
Philips began investigating the possibility of building a magnetic
biodetector in 2001, two years after a team of researchers at the Naval
Research Laboratory (NRL) in Washington, DC, first used magnetic sensors
similar to those employed in hard drives to sniff out certain biowarfare
agents. The NRL scientists labeled biological molecules designed to bind
to target agents with magnetic microbeads, and then scanned for the
tagged targets optically and magnetically. The latter approach used the
same giant magnetoresistant (GMR) sensors that read the bits on an
iPod's hard drive. They quickly developed a shoebox-sized prototype
capable of detecting toxins, including ricin and anthrax.
Philips initially developed both a GMR sensor and an optical one that
relies on frustrated total internal reflection (FTIR)--the same
phenomenon that underlies fingerprint scanners and multitouch screens.
The company decided to go the FTIR route in order to exploit its
expertise in building optical sensors for consumer electronics devices,
says Jeroen Nieuwenhuis, technical director of Philips Handheld
Immunoassays, the division responsible for commercializing the biosensor
technology, which goes by the trade name Magnotech.
Moving to an optical detection method also allowed Philips to simplify
the test cartridges that the device employs, making them easier to
mass-produce, says Nieuwenhuis. With the current FTIR-based system, "we
can make simpler cartridges in larger quantities more easily," he adds.
Once the device's sample collector has absorbed enough saliva, it
automatically changes color and can then be snapped into the measurement
chamber, where the saliva and nanoparticles mix. An electromagnet speeds
the nanoparticles to the sensor surface, different portions of which
have been pretreated with one of the five target-drug molecules. If
traces of any of the five drugs are present in the sample, the
nanoparticles will bind to them. If the sample is drug free, the
nanoparticles will bind to the drug-coated sensor surface instead.
The orientation of the magnetic field that first drew the nanoparticles
to the sensor is then reversed, pulling away any nano-labeled drug
molecules that may accidentally have stuck to the sensor surface but
leaving legitimately bound ones in place. This last magnetic trick
promises to reduce what Larry Kricka, a clinical chemist at the
University of Pennsylvania who recently co-authored an article in
Clinical Chemistry on the use of magnetism in point-of-care testing,
calls "a major restraint in such assays": the unintentional capture of
molecular labels on the test surface, a leading cause of both false
positives and false negatives. Kricka is not involved with Philips but
does serve as a consultant to T2 Biosciences, a Cambridge, MA, firm that
promotes a magnetic biosensor based on MRI technology.
During the analysis phase, a beam of light is bounced off the sensor.
Any nanoparticles bound to the surface will change its refractive index,
thereby altering the intensity of the reflected light and indicating the
concentration of drugs in the sample. By immobilizing different drug
molecules on different portions on the sensor surface, the analyzer is
able to identify the drug traces in question. An electronic screen
displays instructions and a simple color-coded readout of the results.
The test takes less than 90 seconds and can detect drugs at
concentrations measured in parts-per-billion using a single microliter
of saliva. The sensor is capable of even greater sensitivity- -it has
been used to detect cardiac troponin, a commonly used indicator of heart
attack, at concentrations 1,000 times lower.
Philips plans ultimately to enter the healthcare market. It is working
on a platform capable of testing blood as well as saliva and is seeking
partners that can help expand its testing menu by providing it with
Other researchers have built experimental devices to magnetically detect
a wide range of biomolecules in minuscule samples of blood or saliva at
extremely low concentrations. Often this involves using microfluidic or
magnetic forces to quickly shepherd the magnetically labeled molecules
through scanners--though a group at the University of Utah has even
built a prototype in which a sample-laden stick is swiped across a GMR
sensor, like a credit-card through a reader.
The combination of high sensitivity, low sample volumes,
miniaturization, speed, and ease of use has raised hopes for a handheld
biosensor that could perform sophisticated tests with high accuracy.
"Everyone's trying to get there," says Kricka. "The question is who's
going to win?" With Philips set to introduce its drug tester in Europe
by the end of the year in partnership with the British diagnostics firm
Cozart, the consumer electronics maker appears poised to take the prize.
http://www.technolo gyreview. com/biomedicine/ 23111/