SCI/TECH: Nano-tech Probes Sneak Inside Your Cells

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Their success lies in specially prepared crystalline semiconductors composed of a few hundred or thousand atoms that emit different colors of light when illuminated by a laser. Because these fluorescent probes are stable and nontoxic, they have the ability to remain in a cell’s nucleus — without harming the cell or fading out — much longer than conventional fluorescent labels. This could give biologists a ringside seat to nuclear processes that span several hours or days, such as DNA replication, genomic alterations, and cell cycle control. The long-lived probes may also allow researchers to track the effectiveness of disease-fighting drugs that target these processes.

In nature, a virus called SV40 is coated with a protein that binds to a cell’s nuclear trafficking mechanism, a ploy that gives the virus an unhindered ride inside the nucleus. Chen and Gerion obtained a portion of this protein and attached it to the quantum dot. The result is a hybrid quantum dot, part biological molecule and part nano-sized semiconductor, that is small enough to slide through the nuclear membrane’s pores and believable enough to slip past the membrane’s barriers.

In the future, they hope to tailor quantum dots to track specific chemical reactions inside nuclei, such as how proteins help repair DNA after irradiation. They have already visualized the dots’ journey from the area surrounding the nucleus to inside the nucleus, a feat that opens the door for real-time observations of nuclear trafficking mechanisms. They also hope to target other cellular organelles besides the nucleus, such as mitochondria and Golgi bodies. And because quantum dots emit different colors of light based on their size, they can be used to observe the transfer of material between cells.


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