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  • Optical Sensor Catches Drug Abusers

Photonics Spectra
Aug 1999
Max Glaskin

CAMBRIDGE, UK -- Optical sensors that detect biochemical reactions at the molecular level could be used to spot drug abuse by athletes within minutes. The technology promises to be a great improvement over traditional chemical analysis of blood or urine samples that can take several hours to complete.

In addition to the time savings, the new biosensor designs from Labsystems Affinity Sensors could be three times more sensitive than those that are available now. The company expects to complete the sensors soon.

Labsystems' current biosensors are based on a resonant mirror design, in which a 670-nm laser beam enters a prism (which measures 9 x 7 x 6 mm3), coupling through a low-refractive-index spacer to a high-refractive-index waveguide.

When the beam hits a special layer on one surface of the prism, a change in refractive index shows that a biochemical interaction has taken place, indicating the presence of a specific drug. If the sample is drug-free, no biochemical reaction will occur and the light reflects at the expected angle.

Sensitivity factors

Various elements can affect the sensitivity of such sensors -- for example, the penetration depth of the evanescent wave, light loss, instrument noise and temperature variation. Labsystems will not disclose its specific proprietary methods of avoiding problems with these issues.

Increased sensitivity allows the detection of even smaller molecules, which in turn enables the use of less material for the sensing surfaces and reduced operating costs.

With the current systems, tests can be performed for two drugs simultaneously, but the expected improvements will go even further. Extending the number of simultaneous measurements should broaden the technology's application, noted Nikoletta Athanassopoulou, a physicist at Labsystems.

"The molecular weight of [some] drugs used illegally by athletes tends towards the lower limit that current [optical] systems can detect," Athanassopoulou said.

"And there are many pharmaceutical, biochemical and environmental applications that could be carried out when sensitivity is enhanced," she added.

The systems cost £35,000 to £120,000 (approximately $55,590 to $190,600).

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