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Analytical Chemistry

Metal Nanoparticles Can Be Used As Universal Probe For Many Imaging Methods

by Celia Henry Arnaud
September 5, 2011 | A version of this story appeared in Volume 89, Issue 36

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Credit: Courtesy of Jie Zheng
Metal nanoparticles can be used for imaging cancer cells with fluorescence microscopy.
Brain cancer cell labeled with metal nanoparticles and imaged with fluorescence microscopy.
Credit: Courtesy of Jie Zheng
Metal nanoparticles can be used for imaging cancer cells with fluorescence microscopy.

A new type of nanoparticle works as a label for five types of microscopy. Different microscopy methods usually require different types of probes, making the resulting images difficult to correlate. Chemistry professor Jie Zheng and graduate student Chen Zhou of the University of Texas, Dallas, reported that metal nanoparticles can be used as universal probes for five types of microscopy—bright field, dark field, fluorescence, Raman, and two-photon excitation. Zheng attributed the particles’ versatility to a structural phenomenon that he called the grain-size effect. “Each individual nanoparticle is composed of many tiny grains,” Zheng said. Those grains have two distinct size distributions within the particles. That structure gives each highly polycrystalline silver nanoparticle its strong and robust single-particle luminescence, Zheng said. His team decorated the nanoparticle’s surface with peptides that bind to integrin receptors on cell surfaces. With the probe, the researchers imaged brain cancer cells at the single-particle level using multiple types of microscopy.

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Credit: Courtesy of Jie Zheng
TEM image of silver nanoparticles used to label brain cancer cells that was then imaged using five types of microscopy—bright field, Raman, dark field, fluorescence, and two-photon fluorescence
Credit: Courtesy of Jie Zheng

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