One Label, Five Microscopies

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.