Researchers at Berkeley Lab’s Molecular Foundry created upconverting nanoparticles (UCNPs) from nanocrystals of sodium yttrium fluoride (NaYF4) doped with ytterbium and erbium that can be safely used to image single proteins in a cell without disrupting the protein’s activity. (Image by Andrew Mueller)
The term a "brighter future" might be a cliché, but in the case of ultra-small probes for lighting up individual proteins, it is now most appropriate. Researchers at the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have discovered surprising new rules for creating ultra-bright light-emitting crystals that are less than 10 nanometers in diameter. These ultra-tiny but ultra-bright nanoprobes should be a big asset for biological imaging, especially deep-tissue optical imaging of neurons in the brain. Working at the Molecular Foundry, a DOE national nanoscience center hosted at Berkeley Lab, a multidisciplinary team of researchers led by James Schuck and Bruce Cohen, both with Berkeley Lab's Materials Sciences Division, used advanced single-particle characterization and theoretical modeling to study what are known as "upconverting nanoparticles" or UCNPs. Upconversion is the process by which a molecule absorbs two or more photons at a lower energy and emits them at higher energies. The research team determined that the rules governing the design of UCNP probes for ensembles of molecules do not apply to UCNP probes designed for single-molecules. "The widely accepted conventional wisdom for designing bright UCNPs has been that you want to use a high concentration of sensitizer ions and a relatively small concentration of emitter ions, since too many emitters will result in self-quenching that leads to lower brightness, says Schuck, who directs the Molecular Foundry's Imaging and Manipulation of Nanostructures Facility.
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