Aug. 30, 2002 — Researchers at Northwestern University reported today a new technique of detecting infectious diseases using gold nanoparticles that bypasses a potentially time-consuming step required in competing approaches. The Northwestern team said its method provides a way to spot life-threatening bacteria and viruses such as anthrax, smallpox and HIV.

The work appears in the Aug. 30 issue of the journal Science. Lead researcher Chad Mirkin, director of Northwestern’s Institute for Nanotechnology and a chemistry professor, devised a system that relies on chips, gold particles and a treatment step to detect unique biological markers. Each chip and particle is dotted with bits of DNA, the genetic material that defines life forms. The particle, which is 13 nanometers in diameter, also holds a light-sensitive molecule.

If the targeted disease exists in the sample, its DNA will bind onto the complementary strands of DNA on the chip. That attracts the DNA-studded nanoparticle, which latches onto the site as well. The chip is then washed and treated with silver-based photographic developing solution, allowing the silver to coat the nanoparticles. Laser light scanned across the chip detects and records any signals from the chip.

Mirkin said the silver enhances the signal enough to detect minute amounts of DNA. Existing technologies use PCR, or polymerase chain reaction, to replicate bits of DNA to detectable amounts. Typically PCR requires a heating and cooling system and is done in a lab under the supervision of a scientist. Getting results may take days or longer.

Nanosphere Inc., an Illinois-based life sciences startup co-founded by Mirkin, is licensing the nanoparticle technology.