7/01/2008 PERMALINK
Creating nano-spies to infiltrate cells & report back A team of Duke University materials engineers and chemists has developed tiny gold nanostructures that can create signals from subtle changes in light reflecting off their nanoscale surfaces. The sub-cellular size of the nanostructures and their ability to absorb or scatter light as their structure changes makes them appealing as biological sensors suited to creating tiny “spies” able to infiltrate individual cells and report back in real time on the cell’s inner workings, the researchers said.

By measuring color changes, researchers can tell what is happening at the molecular level, said lead researcher Anne Lazarides, assistant professor of mechanical engineering and materials science at Duke’s Fitzpatrick Institute for Photonics. But while these light-reporting particles are relatively easy to see, it is a challenge to get things that small organized. “When dealing in such small realms, it is important that any nanostructure be able to assemble itself in a reliable and predictable fashion,” she said. “We engineered a structure whose organization and response to light are both reproducible and well-controlled.” Because they are just a few thousandths the size of a living cell, nanoparticles are small enough to pass through cell membranes, another reason they are an attractive potential biomedical sensor.

The Duke construct is known as a “core-satellite” structure, resembling a planet with numerous smaller moons tethered to it by tiny strands of DNA. Gold core particles and smaller satellite particles are mixed together in solution with strands of DNA and under controlled circumstances assemble themselves into the desired core-satellite structure. “In order for a nanostructure to work within a living system, it needs to include a biological component, like DNA, that recognizes other molecules,” Lazarides said. “DNA is both the glue that holds all the particles together and also the material to which specific target molecules bind.” The results of Lazarides’ experiments were published online in Nano Letters, a journal published by the American Chemical Society.