M.D.
on a Chip - Next time you feel sick, your doctor might use
your blood sample, plus one tiny computer chip, to rule out up
to 10,000 diseases—all while you’re still there in
the office. (2/6/03)
Cell
Scouts - It’s a short movie that will never make it
to the big screen. Nevertheless, it may have a big role in fighting
disease. (8/28/02)
Elsewhere on the web
Noisy
Inner Life of Cells
Biomolecules
and Nanotechnology
National Institutes
of Health: The Structures of Life
For anyone who’s diagnosed with cancer, doctors often prescribe radiation
and chemotherapy. But some tumors resist these standard treatments. Right
now researchers don’t know why, because it’s been very difficult
to learn how cells actually work.
As this ScienCentral News video reports, one scientist has come up with a better
tool for figuring out why some tumors don’t surrender to medicine’s
arsenal.
Bright Lights off Broadway
At Rockefeller University
in New York City, biologist Sanford
Simon is studying living cells, to find out why some cells organize themselves
into tumors that resist standard cancer treatments. Until recently, he says,
scientists had to study cell organization by looking at cross sections of
dead tissue on slides under a microscope. “It was as if you wanted to
study heart beat and blood circulation, but you only looked at cadavers,”
Simon recalls. “You had no sense of the heart moving or blood flowing
through veins.”
Biologists tried to follow the movements and interactions inside cells by
staining
their components with fluorescence. But the only fluorescent stains available
didn’t come in a wide range of clear colors. Even more problematic,
they bleached away in less than a minute. According to Simon, it was impossible
to follow how a cell worked—only to get “a very brief glimpse
of a cell at work during a few seconds.”
Then, in the early 1980s, a Russian physicist who was working on
miniature
semiconductors saw a byproduct of his work fall to the bottom of his test
tube. These were quantum dots, minute crystals made of two metals, selenium
and cadmium. Each quantum
dot is only about the size of an average molecule, and can emit a neon-bright
color when it is struck by ultraviolet light. Depending on size, quantum dots’
colors span the entire spectrum visible in a rainbow.
Biologists immediately recognized that quantum dots offered distinct advantages
for studying cell organization. Inside a cell, quantum dots give off very
clear, sharp colors—for an indefinite period of time. However, “in
science,” Simon points out, “it’s very easy to come up with
an idea. It’s much harder to figure out how to make that idea work in
practice.”
Quantum dots’ cadmium core is highly poisonous, and physicists had been
using the dots in a solution of chloroform, which also can be toxic. So biologists
spent the next decade working on coatings and other solutions that would allow
them to fix quantum dots onto cell components, without killing off the cells
they wanted to study.
Today, Simon says, he has the means to use quantum dots safely. Because they
remain stable inside cells, without fading or decaying, they have accelerated
his work considerably. Most recently, he has found that if he
starves
particular cells of their nutrients, they herd together and concentrate
themselves. Their behavior under stress may provide him with clues to the
reasons why some tumors resist bombardment with radiation and chemotherapy.
Simon's work was funded by the National Institutes of Health (NIH), National Science Foundation (NSF), and the American Cancer Society.
