March 16, 2006, Houston, TX--Researchers at Rice University have invented "nanorice," rice-shaped particles of gold and iron oxide that may be useful for imaging proteins and other large biomolecules. As described online in the April 12 issue of Nano Letters, nanorice particles are designed to interact with light and focus energy into a small space. Initial tests indicate they may be the most sensitive surface plasmon resonance nanosensors yet devised.
"On the nanoscale, the shape of a particle plays a critical role in how it interacts with light," said Naomi Halas, director of the Laboratory for Nanophotonics at Rice University, who discussed the findings this week at a meeting of the American Physical Society in Baltimore, MD. "We were looking for a new shape that would combine the best properties of the two most optically useful shapes, spheres and rods. It's just a coincidence that that shape turned out to look exactly like a grain of rice."
Nanoparticles like nanorice can be used to focus light on small regions of space. The Rice University scientists plan to capitalize on this by attaching grains of nanorice to scanning probe microscopes. By moving the grains next to proteins and unmapped features on the surfaces of cells, they hope to get a far clearer picture than what's available with current technology.
In form, nanorice is similar to nanoshells, a spherical nanoparticle Halas invented in 1998 that is currently being examined for possible applications in molecular imaging, cancer treatment, medical diagnostics and chemical sensing. Both nanorice and nanoshells are made of a non-conducting core that is covered by a metallic shell.
Halas' investigations find that nanorice possesses far greater structural tunability than nanoshells and another commonly studied optical nanoparticle, the nanorod. In fact, tests indicate that nanorice is the most sensitive surface plasmon resonance (SPR) nanosensor yet devised.