New device offers roadside dope test

Later this year, Philips will introduce a handheld electronic device that uses magnetic nanoparticles to screen for five major recreational drugs.

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 methamphetamine...

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...

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.