March 2003

Bright Lights, Molecular World

By David Talbot

The glow of fluorescent probes has become a critical lighthouse in biomedicine, serving an essential role in many diagnostic, forensic, pharmaceutical, and genomic screening tests. Currently available tests for early detection of HIV, for example, use a probe molecule-a specific protein combined with a light-emitting molecule-that glows when it encounters the RNA of HIV. The glow is detectable by an optical sensor. Researchers at the University of California, Santa Barbara, have developed a simple way to amplify these signals from the molecular world.

The key is a new class of light-emitting polymers that release their optical energy when they come into contact with the probes, boosting the glow by a factor of 25, says Guillermo Bazan, a materials scientist at Santa Barbara. This amplification could mean far more sensitive tests. In fact, says Bazan, "we can detect lower concentrations of HIV's RNA than any of the optical methods today for direct HIV detection."

Equally important is the potential to reduce costs. Fluorescent probes are expensive, and the Santa Barbara technology could mean much less probe material will be needed for diagnostic tests. The new technology would be welcome in developing countries where many people go untreated simply because HIV tests are too expensive.

Applications extend well beyond early detection of HIV. Because fluorescent probes are commonly used to identify specific DNA sequences, light amplification with Bazan's polymers could boost the sensitivity and reduce the cost of procedures ranging from forensic DNA matching to gene tracking in crops. Polymers for brighter fluorescent probes could be ready for genomic research in a year or two, says Bazan, who is working with colleagues to boost fluorescence a hundredfold. Better blood-screening tests and other diagnostics using the polymers could be on the market within three years.