posted on Apr, 28 2005 @ 09:36 AM
A California laboratory has succeeded in creating nano-sized probes, biological and technological hybrids called "Quantum Dots", which can sneak
into the interior of living cells. The probes, no larger than a few hundred or thousand atoms, are able to pass through the cell's previously
impenetrable nuclear membrane by mimicking the protein layer 'cloaking' observed in certain viruses.
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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While still a "passive" form of nano-sized biotechnology, this development is an important step in the quest to one day produce tiny machines that
will be able to repair cells from the inside, effectively reproducing, or even improving on, nature's own complex sub-cellular mechanisms. Creation is
vast and complex, yet many of it's greatest mysteries are contained within the tiny confines of a single cell.
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