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Fluorescent, glowing polymer dot
nanoparticles in solution, illuminated with a UV lamp.
Microscope image of individual fluorescent "polymer
dot" nanoparticles spread out on a glass slide.
Images � by Jason McNeill, Clemson University
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If scientists could track the motion of a
single molecule within a living cell it could reveal a world of
information. Among other things, scientists could determine how
viruses invade a cell or how proteins operate in the body. Such
technology also could help doctors pinpoint the exact location of
cancer cells in order to better focus treatment and minimize damage to
healthy tissue. Outside the body, the technology could help speed up
detection of such toxins as anthrax.
The key to developing single-molecule tracking
technology may be the development of better fluorescent nanoparticles.
Fluorescent nanoparticles are thousands of times
smaller than the width of a human hair and are similar in size to
protein molecules, to which they can be attached. When illuminated by
a laser beam inside a light microscope equipped with a sensitive
digital camera, the nanoparticle attached to a protein will light up,
allowing scientists to get a precise fix on the position of the
protein and monitor its motion inside a cell.
Until now, nanoparticles have been too dim to
detect inside cells, but Clemson chemists have developed a novel type
of nanoparticles containing materials called conjugated polymers that
light up and stay lit long enough for scientists to string together
thousands of images, as in a movie.
Conjugated polymers share many properties with
semiconductors like silicon but have the flexibility of plastic. While
initial efforts at preparing nanoparticles out of conjugated polymers
resulted in particles that were very bright, their brightness quickly
faded under the bright glare of a laser beam.
�When a conjugated polymer is in a high energy
state, it is vulnerable to attack by oxygen,� says principal
investigator and chemist Jason McNeill. �The dye efficiently removes
the energy from the molecule and re-emits the energy as light, which
greatly improves the brightness and longevity of the nanoparticles.�
McNeill says other possible targets of
investigation include the formation of plaques and fibrils in the
brain associated with Alzheimer's disease and mad cow disease.
Graduate students Changfeng Wu, Craig Szymanski, Jennifer Grimland and
Yueli Zheng contributed to the study, which the National Science
Foundation funded.
Clemson University chemists are presenting 40
papers on a wide range of subjects at the society meeting. Other
topics include detection and quantification of uranium in groundwater,
conversion of lipid feedstocks such as poultry fat to biodiesel and a
new mechanism for antioxidants that fight DNA damage. |
