Researchers Develop Ultrabright Nanocrystals for Single Protein Imaging
25 March 2014
US researchers have recently created ultrabright light-emitting crystals with extremely small size that have the capacity to image single proteins. The discovery could bring significant benefits to biological imaging processes by enabling deep-tissue optical observations of neurons in the brain.
The nanoprobes, which are less than ten nanometers in diameter, were developed by a team from Lawrence Berkeley National Laboratory at the US Department of Energy. The scientists used novel single-particle characterization and theoretical modeling to examine the properties of upconverting nanoparticles (UCNPs), which are made out of nanocrystals of sodium yttrium fluoride doped with ytterbium and erbium, given their potential to safely image single proteins in a cell without disrupting its activity.
The team found, however, that the rules applying to the design of UCNP probes for ensembles of molecules are not valid for UCNP probes for single molecules. In order to make UCNPs more compatible with cellular imaging, the researchers needed to think of new synthetic methods to shrink their size, said Bruce Cohen of Berkeley Lab's Materials Sciences division. Their experiments revealed that under the higher excitation powers used for imaging single particles, emitter concentrations must be as high as possible without affecting the structure of the nanocrystal, said James Schuck, also of Berkeley Lab.
UCNPs that are heavily doped with erbium are weak at low powers, but by the time the laser intensity is boosted, they have passed up the conventionally doped UCNPs that are the highflyers at low powers, researcher Emory Chan added.