One such quantum property is the ability to absorb light of any wavelength and re-emit that light at only one specific frequency or color. In other words, quantum dots glow, and the larger the dot, the redder their color. Physicists have learned how to manufacture quantum dots in a variety of sizes that glow in any visible color, from red to blue through ultraviolet. Getting silicon to glow in such a manner has long been the key to transforming many optical computing concepts into working hardware. With quantum dots, that door is open and exciting research continues.

Now, as reported in the November 29 issue of Science, a team of biologists report creating the first glowing quantum dot frog. Being positively charged, raw quantum dots will not mix with or dissolve in water. Researchers from the Rockefeller University have learned how to coat quantum dots with a micelle, which is a class of chemical used to coat insoluble drugs. This has enabled them to inject billions of quantum dots into a fertilized frog egg, turning the egg into a sort of microscopic snow globe paperweight. As the egg divided into an increasingly complicated multicellular embryo, quantum dots naturally flowed into each cell during the appropriate cell division time. Without harming or interfereing with the normal embryogeic process, the biologists were thus able to place glowing “fluid flow” markers into the cellular fluid of each cell. “We’ve seen quantum dots dispersed throughout the cytoplasm of early embryonic cells suddenly relocalize to the nuclei about four hours after fertilization,” says one of the scientists involved in the research. “This indicates the onset of embryonic transcriptional activity; visualization with quantum dots is the first in vivo marker of this important developmental stage.”

“We always knew this physics/biology collaboration would bear fruit,” says another researcher, “we just never knew how sweet it would be. Quantum dots in vivo are the most exciting, and beautiful, scientific images I have ever seen.”

Besides obvious research applications, the biologically compatable quantum dots offer one possible way to uniquely mark or label via taggants those organisms such as clones or in-vitro babies that are created by the manipulation of single cells.